{"id":5641,"date":"2019-03-16T13:05:49","date_gmt":"2019-03-16T17:05:49","guid":{"rendered":"https:\/\/dronebotworkshop.com\/?p=5641"},"modified":"2023-04-12T11:42:46","modified_gmt":"2023-04-12T15:42:46","slug":"sd-card-arduino","status":"publish","type":"post","link":"https:\/\/dronebotworkshop.com\/sd-card-arduino\/","title":{"rendered":"SD Card Experiments with Arduino"},"content":{"rendered":"\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-9571 size-full alignnone\" title=\"Download PDF\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2023\/04\/dbws-pdfdown.png?resize=64%2C64&#038;ssl=1\" alt=\"Download PDF\" width=\"64\" height=\"64\" data-recalc-dims=\"1\" \/> <a href=\"#Parts_List\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-9563 size-full\" title=\"Parts List\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2023\/04\/dbws-parts.png?resize=64%2C64&#038;ssl=1\" alt=\"Parts List\" width=\"64\" height=\"64\" data-recalc-dims=\"1\" \/><\/a> <a href=\"https:\/\/youtu.be\/PQhQfww-qGQ\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-9565 size-full\" title=\"View on YouTube\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2023\/04\/dbws-youtube.png?resize=64%2C64&#038;ssl=1\" alt=\"View on YouTube\" width=\"64\" height=\"64\" data-recalc-dims=\"1\" \/><\/a> <a href=\"https:\/\/s3.amazonaws.com\/download.dronebotworkshop.com\/SD+Servo+Record+Play+DroneBot+Workshop.zip\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-9569 size-full\" title=\"Download Code\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2023\/04\/dbws-codedown.png?resize=64%2C64&#038;ssl=1\" alt=\"Download Code\" width=\"64\" height=\"64\" data-recalc-dims=\"1\" \/><\/a><\/p>\n<h2><span style=\"font-weight: 400;\">Introduction<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Secure Digital, or SD, Cards are used in a variety of applications. You likely have several of them in your electronic devices as they are used in phones, tablets, cameras, and music players.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The Raspberry Pi also uses a microSD card for storage, in a sense it performs the function of a hard drive.<\/span><\/p>\n<div class=\"youtube-player\" data-id=\"PQhQfww-qGQ\"><\/div>\n<p><span style=\"font-weight: 400;\">Anywhere that you need a large amount of inexpensive, non-volatile memory an SD (or microSD) card is a good choice. And, as you are about to see, these cards are very easy to use in your Arduino projects.<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">SD and microSD Cards<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">The SD card was developed as a joint effort between SanDisk, Panasonic, and Toshiba. The first SD cards were released in August 1999. In January 2000 the three companies formed the <\/span><a href=\"https:\/\/www.sdcard.org\/index.html\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"font-weight: 400;\">SD Association<\/span><\/a><span style=\"font-weight: 400;\"> to create standards for SD cards.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5651\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/SD-Cards-With-Arduino.jpeg?resize=750%2C422&#038;ssl=1\" alt=\"SD Cards with Arduino\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/SD-Cards-With-Arduino.jpeg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/SD-Cards-With-Arduino.jpeg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">There are actually three sizes of SD cards &#8211; standard SD cards, miniSD cards, and microSD cards. The miniSD card was never that popular and hasn\u2019t been produced since 2008 so modern devices make use of either standard SD cards or microSD cards.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">There are also a number of designations on SD cards such as \u201cSDXC\u201d, SDUC\u201d, \u201cUHS-I\u201d, \u201cClass 10\u201d etc. This can get a bit confusing when trying to choose an SD card.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The following is an (admittedly lame) attempt to clarify some of this!<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">File Systems<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">SD Cards have evolved to use different file systems, different speeds, and different connection methods than the original 1999 design. \u00a0These differences are designated into five different storage classes:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><b>SD or SDSC<\/b><span style=\"font-weight: 400;\"> &#8211; Standard Capacity SD cards. These use the FAT32 file system and can store up to 2 GB of data. \u00a0Older cards used the FAT16 file system.<\/span><\/li>\n<li style=\"font-weight: 400;\"><b>SDHC<\/b><span style=\"font-weight: 400;\"> &#8211; These are High Capacity cards. They also use the FAT32 file systems and can store from 2 GB to 32 GB of data.<\/span><\/li>\n<li style=\"font-weight: 400;\"><b>SDXC<\/b><span style=\"font-weight: 400;\"> &#8211; These are Extended Capacity cards. \u00a0They use the exFAT file system and have capacities from 32 GB to 2 TB.<\/span><\/li>\n<li style=\"font-weight: 400;\"><b>SDUC<\/b><span style=\"font-weight: 400;\"> &#8211; These are Ultra Capacity cards. They have capacities from 2 TB to a whopping 128 TB.<\/span><\/li>\n<li style=\"font-weight: 400;\"><b>SDIO<\/b><span style=\"font-weight: 400;\"> &#8211; This is a standard that combines memory cards with Bluetooth and other wireless networking standards, allowing the cards to be read remotely.<\/span><\/li>\n<\/ul>\n<h3><span style=\"font-weight: 400;\">Speed<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">SD cards are serial data cards and thus have limits to the speed that they can transfer data. As SD cards evolved so has their speeds and there are new designations to determine which cards are faster than others.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Older cards used a Class designation from 1 to 10, with a 10 being the fastest. Modern SD cards can all exceed Class 10 speed so the class designation is virtually meaningless.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">SDHC and SDXC cards can use an Ultra High-Speed bus and have the following designations:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">UHS-I &#8211; Transfers data at a rate of 50 MBps to 104 MBps.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">UHS-II &#8211; Transfers data at a rate of 156 MBps.<\/span><\/li>\n<li style=\"font-weight: 400;\"><span style=\"font-weight: 400;\">UHS-III &#8211; Transfers data from 312 MBps to 624 MBps.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">There is also a new specification called \u201cSD Express\u201d which can transfer data at up to 985 MBps.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Electrical Connections<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">A standard SD card uses the SPI bus and works at 3.3 volts. \u00a0SDHC and SDXC cards can also switch to the \u201cone-bit SD bus\u201d and in this mode they work on 1.8 volts.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">When an SDHC or SDXC card is inserted into its socket it will initially use the SPI bus. The host computer can switch the device to one-bit mode if the device supports it.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">SD cards and microSD cards are electrically compatible, however, they do not use the same pinouts. The plastic \u201cSD Adapter\u201d that is usually included with microSD cards is wired to reconfigure the pinout so the microSD card can also be used in an SD card slot.<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">SD Card Modules for Arduino<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">There are many SD card modules available for the Arduino. \u00a0Some of them are stand-alone, others are shields. Many of the shields also have additional components like real time clocks, Ethernet adapters and temperature sensors integrated along with the SD card holder.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5650\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/SD-and-microSD-Modules.jpg?resize=750%2C422&#038;ssl=1\" alt=\"SD and microSD Modules for Arduino\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/SD-and-microSD-Modules.jpg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/SD-and-microSD-Modules.jpg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">In the experiments I&#8217;ll be performing I used a microSD card adapter, however you can substitute a shield of full-sized SD card adapter if you wish.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Standard SD Modules<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">The full-sized SD card modules I\u2019ve used have SPI bus connections and connections for either a 5-volt or 3.3-volt power supply.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The SD card uses 3.3-volt logic so there is a built-in voltage regulator to reduce the 5-volt supply to 3.3-volts. If you use a 3.3-volt supply the regulator is bypassed.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">One thing to note is that many of these modules do not have logic-level converters and therefore expect that 3.3-volt logic will be used. If you are using 5-volt logic, as with an Arduino Uno or Mega, you\u2019ll need to supply logic-level converters or use a resistor array to work with the 3.3-volt logic.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">microSD Modules<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">In my experiments I elected to use the microSD module, the one I\u2019m using is very common. <\/span><\/p>\n<p><span style=\"font-weight: 400;\">These modules are made to be used with 5-volt logic as they contain built-in logic converters, as well as voltage regulators. As such they have only a 5-volt power input.<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">Using SD Cards with Arduino<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">The Arduino does not have a particularly fast bus so any type of SD card will work well with it.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">I\u2019ll be showing you the connections using a microSD module but they are pretty well identical for a full-sized SD module. Remember though that if you elect to use a full-sized module you may need to do some logic-level conversion, otherwise your data will be garbled.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Hooking up the microSD Module<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">The following diagram shows how to hoo the microSD card module to the Arduino Uno, using the SPI bus.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5646\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-SD-Card-Hookup-.jpeg?resize=750%2C422&#038;ssl=1\" alt=\"Arduino SD Card Module Hookup\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-SD-Card-Hookup-.jpeg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-SD-Card-Hookup-.jpeg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">If you are using a shield with an SD or microSD card you might need to change the Chip Select (CS) pin connection, the one I have connected to pin 4. Some shields use pin 6 or pin 10, check with your shield manufacturer or use a multimeter to determine if this is the case with your shield<\/span><\/p>\n<p><span style=\"font-weight: 400;\">If you are using an Arduino Mega the SPI pin connections are different. \u00a0The following table shows the relationship between the Uno and the Mega.<\/span><\/p>\n<table style=\"height: 307px;\" width=\"768\">\n<tbody>\n<tr style=\"background-color: #6495ed; color: #ffffff;\">\n<td><b>SPI Bus Connect<\/b><\/td>\n<td><b>Arduino Uno<\/b><\/td>\n<td><b>Arduino Mega<\/b><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">MISO<\/span><\/td>\n<td><span style=\"font-weight: 400;\">12<\/span><\/td>\n<td><span style=\"font-weight: 400;\">50<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">MOSI<\/span><\/td>\n<td><span style=\"font-weight: 400;\">11<\/span><\/td>\n<td><span style=\"font-weight: 400;\">51<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">SCK<\/span><\/td>\n<td><span style=\"font-weight: 400;\">13<\/span><\/td>\n<td><span style=\"font-weight: 400;\">52<\/span><\/td>\n<\/tr>\n<tr>\n<td><span style=\"font-weight: 400;\">CS<\/span><\/td>\n<td><span style=\"font-weight: 400;\">4 (can be another pin)<\/span><\/td>\n<td><span style=\"font-weight: 400;\">53 (can be another pin)<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><span style=\"font-weight: 400;\">Again note that you can use almost any pin for Chip Select (CS), so if you do change it just remember to change the appropriate line in the sketch to reflect the difference.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Arduino SD Library<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">The Arduino IDE already has a <\/span><a href=\"https:\/\/www.arduino.cc\/en\/reference\/SD\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"font-weight: 400;\">library for working with SD cards<\/span><\/a><span style=\"font-weight: 400;\">. It supports both FAT16 and FAT32 file systems on both standard SD (SDSC) or SDHC cards. \u00a0Keep that in mind if you are reformatting your microSD card and don\u2019t use exFAT.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Another thing to remember is it uses the older 8.3 naming convention for file names, so keep your names down to 8-characters or less with a maximum 3-character extension. \u00a0A name like \u201cTESTFILE.TXT\u201d is great, one like \u201cMYNICEFILE.FILE\u201d won\u2019t work.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">You can also use forward slashes (\u201c\/\u201d) to specify directories if you need to.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The Arduino also has the <\/span><a href=\"https:\/\/www.arduino.cc\/en\/reference\/SPI\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"font-weight: 400;\">SPI Library<\/span><\/a><span style=\"font-weight: 400;\"> for communicating over the SPI bus, you\u2019ll need that to talk to your SD or microSD card module.<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">Arduino Example Sketches<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">The Arduino SD Library has a number of example sketches included with it, and they are great for learning how to work with an SD card.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">You can access these libraries by opening the <\/span><i><span style=\"font-weight: 400;\">File<\/span><\/i><span style=\"font-weight: 400;\"> menu and selecting <\/span><i><span style=\"font-weight: 400;\">Examples<\/span><\/i><span style=\"font-weight: 400;\">. From the sub-menu scroll down until you get to the <\/span><i><span style=\"font-weight: 400;\">SD<\/span><\/i><span style=\"font-weight: 400;\"> entry and highlight that. You\u2019ll see six example sketches that you can try.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">We will look at a few of them now.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">ReadWrite<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">The first example we will look at is the ReadWrite example. As its name would imply it shows you how to read and write data from an SD card.<\/span><\/p>\n<pre class=\"lang:default decode:true \" title=\"ReadWrite\">\/*\r\n  SD card read\/write\r\n\r\n This example shows how to read and write data to and from an SD card file\r\n The circuit:\r\n * SD card attached to SPI bus as follows:\r\n ** MOSI - pin 11\r\n ** MISO - pin 12\r\n ** CLK - pin 13\r\n ** CS - pin 4 (for MKRZero SD: SDCARD_SS_PIN)\r\n\r\n created   Nov 2010\r\n by David A. Mellis\r\n modified 9 Apr 2012\r\n by Tom Igoe\r\n\r\n This example code is in the public domain.\r\n\r\n *\/\r\n\r\n#include &lt;SPI.h&gt;\r\n#include &lt;SD.h&gt;\r\n\r\nFile myFile;\r\n\r\nvoid setup() {\r\n  \/\/ Open serial communications and wait for port to open:\r\n  Serial.begin(9600);\r\n  while (!Serial) {\r\n    ; \/\/ wait for serial port to connect. Needed for native USB port only\r\n  }\r\n\r\n\r\n  Serial.print(\"Initializing SD card...\");\r\n\r\n  if (!SD.begin(4)) {\r\n    Serial.println(\"initialization failed!\");\r\n    while (1);\r\n  }\r\n  Serial.println(\"initialization done.\");\r\n\r\n  \/\/ open the file. note that only one file can be open at a time,\r\n  \/\/ so you have to close this one before opening another.\r\n  myFile = SD.open(\"test.txt\", FILE_WRITE);\r\n\r\n  \/\/ if the file opened okay, write to it:\r\n  if (myFile) {\r\n    Serial.print(\"Writing to test.txt...\");\r\n    myFile.println(\"testing 1, 2, 3.\");\r\n    \/\/ close the file:\r\n    myFile.close();\r\n    Serial.println(\"done.\");\r\n  } else {\r\n    \/\/ if the file didn't open, print an error:\r\n    Serial.println(\"error opening test.txt\");\r\n  }\r\n\r\n  \/\/ re-open the file for reading:\r\n  myFile = SD.open(\"test.txt\");\r\n  if (myFile) {\r\n    Serial.println(\"test.txt:\");\r\n\r\n    \/\/ read from the file until there's nothing else in it:\r\n    while (myFile.available()) {\r\n      Serial.write(myFile.read());\r\n    }\r\n    \/\/ close the file:\r\n    myFile.close();\r\n  } else {\r\n    \/\/ if the file didn't open, print an error:\r\n    Serial.println(\"error opening test.txt\");\r\n  }\r\n}\r\n\r\nvoid loop() {\r\n  \/\/ nothing happens after setup\r\n}<\/pre>\n<p><span style=\"font-weight: 400;\">The sketch starts by including both the SPI and SD libraries. \u00a0We then define a File object called <\/span><i><span style=\"font-weight: 400;\">myfile<\/span><\/i><span style=\"font-weight: 400;\">.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The whole sketch runs in the setup, so it runs once and then ends.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In the Setup we set the speed for the serial monitor and then write \u201c<\/span><i><span style=\"font-weight: 400;\">Initializing SD card\u2026<\/span><\/i><span style=\"font-weight: 400;\">\u201d to it. \u00a0We then initialize the SD card and print an error message if it fails.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Note the line with <\/span><i><span style=\"font-weight: 400;\">SD.begin(4)<\/span><\/i><span style=\"font-weight: 400;\"> in it. The number \u201c<\/span><i><span style=\"font-weight: 400;\">4<\/span><\/i><span style=\"font-weight: 400;\">\u201d is the pin that the Chip Select (CS) of the module is connected to. If you&#8217;re using a shield which uses a different pin you\u2019ll need to change this line to the proper value.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Assuming that the card is OK we then open a file. Take a good look at this statement as it is key to understanding how to work with the file system.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The <\/span><i><span style=\"font-weight: 400;\">SD.open<\/span><\/i><span style=\"font-weight: 400;\"> opens the file. We specify the file name and then we add the <\/span><i><span style=\"font-weight: 400;\">FILE_WRITE <\/span><\/i><span style=\"font-weight: 400;\">parameter to indicate that we want to write to the file. \u00a0If we hadn\u2019t specified that the file would be open to read instead.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">If the file does not exist it will be created and opened. If it already exists then it will be opened and any text we add wil be appended to it. This is an important point to note.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">We write to the serial monitor and then use <\/span><i><span style=\"font-weight: 400;\">myFile.println<\/span><\/i><span style=\"font-weight: 400;\"> to write to the file itself.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">After that we close the file. Again, this is an important point to note when working with files, you need to close them when you are done with them.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">After we write to the file we open it again, this time to read from it. Note that this time we only need to specify the file name.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Compile the sketch and send it to your Arduino, make sure that you have a microSD card in your module and that it is formatted with the FAT32 file system. \u00a0Then open your serial monitor.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">You should see the text \u201c<\/span><i><span style=\"font-weight: 400;\">testing 1, 2, 3.<\/span><\/i><span style=\"font-weight: 400;\">\u201d displayed on the screen.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5653\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/sd-readwrite-demo.jpg?resize=750%2C422&#038;ssl=1\" alt=\"SD Card ReadWrite Demo\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/sd-readwrite-demo.jpg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/sd-readwrite-demo.jpg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">Try pressing the reset button on your Arduino and observe the serial monitor. You should see an additional line of text every time you press the button. This is because the sketch is appending the text to the file every time it is run.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">DataLogger<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">A Datalogger is a device that can record data over a period of time. It can be used to observe trends or just to record data.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The SD library has a simple Datalogger example. Unlike a professional datalogger, this one does not use a real time clock to add a timestamp to the data, it simply reads the data and writes it to a file on the SD card.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">To use this sketch you will need to add some additional components to the circuit, specifically three potentiometers. These should be linear taper devices, any value from 5k up would work &#8211; I used three 10k pots in my setup.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5645\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-Datalogger-Hookup.jpeg?resize=750%2C422&#038;ssl=1\" alt=\"Arduino SD Datalogger Hookup\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-Datalogger-Hookup.jpeg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-Datalogger-Hookup.jpeg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">The wiper of each potentiometer is connected to one of the Arduino analog input pins, A0, A1, and A2. One side of each pot is connected to the 5-volt output, the other side is connected to ground.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">This will allow you to vary the voltage sent to the analog pins from zero to 5 volts. \u00a0We will measure the voltage and write the value, from 0 to 1023, to the SD card. The results will be saved in a comma-delimited file.<\/span><\/p>\n<pre class=\"lang:default decode:true \" title=\"Datalogger\">\/*\r\n  SD card datalogger\r\n\r\n This example shows how to log data from three analog sensors\r\n to an SD card using the SD library.\r\n\r\n The circuit:\r\n * analog sensors on analog ins 0, 1, and 2\r\n * SD card attached to SPI bus as follows:\r\n ** MOSI - pin 11\r\n ** MISO - pin 12\r\n ** CLK - pin 13\r\n ** CS - pin 4 (for MKRZero SD: SDCARD_SS_PIN)\r\n\r\n created  24 Nov 2010\r\n modified 9 Apr 2012\r\n by Tom Igoe\r\n\r\n This example code is in the public domain.\r\n\r\n *\/\r\n\r\n#include &lt;SPI.h&gt;\r\n#include &lt;SD.h&gt;\r\n\r\nconst int chipSelect = 4;\r\n\r\nvoid setup() {\r\n  \/\/ Open serial communications and wait for port to open:\r\n  Serial.begin(9600);\r\n  while (!Serial) {\r\n    ; \/\/ wait for serial port to connect. Needed for native USB port only\r\n  }\r\n\r\n\r\n  Serial.print(\"Initializing SD card...\");\r\n\r\n  \/\/ see if the card is present and can be initialized:\r\n  if (!SD.begin(chipSelect)) {\r\n    Serial.println(\"Card failed, or not present\");\r\n    \/\/ don't do anything more:\r\n    while (1);\r\n  }\r\n  Serial.println(\"card initialized.\");\r\n}\r\n\r\nvoid loop() {\r\n  \/\/ make a string for assembling the data to log:\r\n  String dataString = \"\";\r\n\r\n  \/\/ read three sensors and append to the string:\r\n  for (int analogPin = 0; analogPin &lt; 3; analogPin++) {\r\n    int sensor = analogRead(analogPin);\r\n    dataString += String(sensor);\r\n    if (analogPin &lt; 2) {\r\n      dataString += \",\";\r\n    }\r\n  }\r\n\r\n  \/\/ open the file. note that only one file can be open at a time,\r\n  \/\/ so you have to close this one before opening another.\r\n  File dataFile = SD.open(\"datalog.txt\", FILE_WRITE);\r\n\r\n  \/\/ if the file is available, write to it:\r\n  if (dataFile) {\r\n    dataFile.println(dataString);\r\n    dataFile.close();\r\n    \/\/ print to the serial port too:\r\n    Serial.println(dataString);\r\n  }\r\n  \/\/ if the file isn't open, pop up an error:\r\n  else {\r\n    Serial.println(\"error opening datalog.txt\");\r\n  }\r\n}<\/pre>\n<p><span style=\"font-weight: 400;\">The Datalogger sketch starts off in a similar fashion to the previous example. You\u2019ll note that a constant named <\/span><i><span style=\"font-weight: 400;\">chipSelect<\/span><\/i><span style=\"font-weight: 400;\"> is assigned to the pin you are using to connect to the CD line on your module. Again, if you are using a shield that connects CS to a different pin you\u2019ll need to adjust that accordingly.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Unlike the last sketch this one operates in the Loop, which makes sense as it will continually read the value of the voltages on the three analog inputs and write them to the file.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The section that reads the sensors is a nice example of efficient programming. Instead of writing a line for each sensor a for loop is used to step through the sensors and to format the text for the comma-delimited text file. You can easily extend this to use more analog ports.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5648\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/datalogger-demo.jpg?resize=750%2C422&#038;ssl=1\" alt=\"SD Card Datalogger Demo\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/datalogger-demo.jpg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/datalogger-demo.jpg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">Load the sketch to your Arduino and open your serial monitor. You will see the values of the three analog inputs displayed, adjust some of the potentiometers and observe how they change.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">After running it for a while power down the Arduino and remove the card. Now insert the card into your computer and read the resulting file. You should see it contains the same data you observed on the serial monitor.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5649\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/read-sd-on-computer.jpg?resize=750%2C422&#038;ssl=1\" alt=\"Read SD Card file on Computer\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/read-sd-on-computer.jpg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/read-sd-on-computer.jpg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">As this is a comma-delimited text file you can also open it up using your preferred spreadsheet and read the data in columns.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">DumpFile<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Reading the file on your computer is useful but not as convenient as using the Arduino to do it. The final example we will take a look at will read the file to the Arduino serial monitor.<\/span><\/p>\n<pre class=\"lang:default decode:true \" title=\"DumpFile\">\/*\r\n  SD card file dump\r\n\r\n This example shows how to read a file from the SD card using the\r\n SD library and send it over the serial port.\r\n\r\n The circuit:\r\n * SD card attached to SPI bus as follows:\r\n ** MOSI - pin 11\r\n ** MISO - pin 12\r\n ** CLK - pin 13\r\n ** CS - pin 4 (for MKRZero SD: SDCARD_SS_PIN)\r\n\r\n created  22 December 2010\r\n by Limor Fried\r\n modified 9 Apr 2012\r\n by Tom Igoe\r\n\r\n This example code is in the public domain.\r\n\r\n *\/\r\n\r\n#include &lt;SPI.h&gt;\r\n#include &lt;SD.h&gt;\r\n\r\nconst int chipSelect = 4;\r\n\r\nvoid setup() {\r\n  \/\/ Open serial communications and wait for port to open:\r\n  Serial.begin(9600);\r\n  while (!Serial) {\r\n    ; \/\/ wait for serial port to connect. Needed for native USB port only\r\n  }\r\n\r\n\r\n  Serial.print(\"Initializing SD card...\");\r\n\r\n  \/\/ see if the card is present and can be initialized:\r\n  if (!SD.begin(chipSelect)) {\r\n    Serial.println(\"Card failed, or not present\");\r\n    \/\/ don't do anything more:\r\n    while (1);\r\n  }\r\n  Serial.println(\"card initialized.\");\r\n\r\n  \/\/ open the file. note that only one file can be open at a time,\r\n  \/\/ so you have to close this one before opening another.\r\n  File dataFile = SD.open(\"datalog.txt\");\r\n\r\n  \/\/ if the file is available, write to it:\r\n  if (dataFile) {\r\n    while (dataFile.available()) {\r\n      Serial.write(dataFile.read());\r\n    }\r\n    dataFile.close();\r\n  }\r\n  \/\/ if the file isn't open, pop up an error:\r\n  else {\r\n    Serial.println(\"error opening datalog.txt\");\r\n  }\r\n}\r\n\r\nvoid loop() {\r\n}<\/pre>\n<p><span style=\"font-weight: 400;\">The DumpFile sketch dumps the contents of the file on the SD card to the serial monitor. As with the first example it works entirely in the Setup routine so there is no code in the loop.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">After opening the file for reading the sketch uses a while statement to read the data line-by-line while it is available. Each line is printed to the serial monitor.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5652\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/sd-dumpfile-demo.jpg?resize=750%2C422&#038;ssl=1\" alt=\"SD Card DumpFile Demo\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/sd-dumpfile-demo.jpg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/sd-dumpfile-demo.jpg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">Run the sketch and open the serial monitor. You should observe the same data you saw in the serial monitor when you initially ran the Datalogger sketch.<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">Servo Motor Recorder &amp; Playback<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">So now that we have looked at some of the SD card example sketches let\u2019s write one of our own.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The sketches I\u2019m about to show you will allow you to record the position of a servo motor and then play it back. Essentially I\u2019ve combined parts of the Datalogger and DumpFile sketches with a simple servo driver.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">You can use this sketch as-is or, better yet, expand upon it to record and playback movements on a robot arm, a robot car or you can use it to create a sequence that plays back on one or more LEDs. <\/span><\/p>\n<p><span style=\"font-weight: 400;\">Although I\u2019m only controlling one servo motor in this example it would be very simple to add more of them.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Arduino Hookup<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">If you still have the Datalogger circuit hooked up on your breadboard you can leave it as it is, we will only be using the potentiometer connected to pin A0. \u00a0Otherwise, you\u2019ll need one potentiometer that is hooked up as follows.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5647\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-Servo-SD-Hookup.jpeg?resize=750%2C422&#038;ssl=1\" alt=\"Arduino Servo and SD Card Hookup\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-Servo-SD-Hookup.jpeg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/Arduino-Servo-SD-Hookup.jpeg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">You will also need a servo motor, along with a power supply for that motor. Although you could hook the servo up to the Arduino 5-volt output I really don\u2019t recommend it, as sharing a servo with the Arduino power supply isn\u2019t a very good idea &#8211; it can induce noise and voltage drops onto the supply lines.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">I used my bench power supply for the external 5-volt supply, you could also use a 6-volt battery if you wish.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">I used a common SG90 servo motor for this test but you can use pretty well any servo you happen to have on hand. <\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Servo Recorder<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">I\u2019ve created two sketches, one that records the servo data onto the SD card and a second one that plays it back. You could expand upon them and include them both in the same sketch, perhaps with some record and playback pushbuttons.<\/span><\/p>\n<pre class=\"lang:default decode:true \" title=\"Servo Record\">\/*\r\n  Servo position recorder\r\n  servo-record.ino\r\n  Records servo movements on SD card\r\n  Displays results on Serial Monitor\r\n  DroneBot Workshop 2019\r\n  <blockquote class=\"wp-embedded-content\" data-secret=\"C5cooh158w\"><a href=\"https:\/\/dronebotworkshop.com\/\">Welcome to the Workshop!<\/a><\/blockquote><iframe class=\"wp-embedded-content\" sandbox=\"allow-scripts\" security=\"restricted\" style=\"position: absolute; clip: rect(1px, 1px, 1px, 1px);\" title=\"&#8220;Welcome to the Workshop!&#8221; &#8212; DroneBot Workshop\" src=\"https:\/\/dronebotworkshop.com\/embed\/#?secret=UAZlaXzhGU#?secret=C5cooh158w\" data-secret=\"C5cooh158w\" width=\"600\" height=\"338\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\"><\/iframe>\r\n*\/\r\n\r\n\/\/ Include libraries\r\n\r\n#include &lt;SPI.h&gt;\r\n#include &lt;SD.h&gt;\r\n#include &lt;Servo.h&gt;\r\n\r\n\/\/ CS pin for SD Card Module\r\nconst int chipSelect = 4;\r\n\/\/ Analog pin for potentiometer\r\nint analogPin = 0;\r\n\/\/ Integer to hold potentiometer value\r\nint val = 0;\r\n\r\n\/\/ Create a Servo object\r\nServo myservo;\r\n\r\nvoid setup() {\r\n\r\n  \/\/ Open serial communications and wait for port to open:\r\n  Serial.begin(9600);\r\n  while (!Serial) {\r\n    ; \/\/ wait for serial port to connect. Needed for native USB port only\r\n  }\r\n\r\n\r\n  Serial.print(\"Initializing SD card...\");\r\n\r\n  \/\/ see if the card is present and can be initialized:\r\n  if (!SD.begin(chipSelect)) {\r\n    Serial.println(\"Card failed, or not present\");\r\n    \/\/ don't do anything more:\r\n    while (1);\r\n  }\r\n  Serial.println(\"card initialized.\");\r\n  \r\n  \/\/ Attach servo on pin 9 to the servo object\r\n  myservo.attach(9);  \r\n}\r\n\r\nvoid loop() {\r\n  \/\/ make a string for assembling the data to log:\r\n\tString dataString = \"\";\r\n\r\n  \/\/ Read pot value and append to the string\r\n  \/\/ Map to range of 0-180 for servo\r\n    val = map(analogRead(analogPin), 0, 1023, 0, 180);\r\n    dataString += String(val);\r\n    \r\n  \/\/ Write to the servo\r\n  \/\/ Delay to allow servo to settle in position\r\n\tmyservo.write(val);\r\n\tdelay(15);\r\n  \r\n\r\n  \/\/ open the file. note that only one file can be open at a time,\r\n  \/\/ so you have to close this one before opening another.\r\n  File dataFile = SD.open(\"servopos.txt\", FILE_WRITE);\r\n\r\n  \/\/ if the file is available, write to it:\r\n  if (dataFile) {\r\n    dataFile.println(dataString);\r\n    dataFile.close();\r\n    \/\/ print to the serial port too:\r\n    Serial.println(dataString);\r\n  }\r\n  \/\/ if the file isn't open, pop up an error:\r\n  else {\r\n    Serial.println(\"error opening servopos.txt\");\r\n  }\r\n}\r\n<\/pre>\n<p><span style=\"font-weight: 400;\">The sketch starts by including libraries for the SPI bus, the SD card module and for the servo motor. All three libraries are part of your Arduino IDE so you don\u2019t need to install anything.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Once again if your SD card is on a shield you might need to change the <\/span><i><span style=\"font-weight: 400;\">chipSelec<\/span><\/i><span style=\"font-weight: 400;\">t constant value to match.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">I also define integers to hold the analog input pin number and to hold the value read from that pin.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Finally, an object called <\/span><i><span style=\"font-weight: 400;\">myservo<\/span><\/i><span style=\"font-weight: 400;\"> is created to represent the servo motor.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The Setup contains code we have seen before with the addition of a line to set up the servo motor and attach it to pin 9. You can use a different pin if you want to, just make sure that it is a pin that supports PWM.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The Loop works in a similar fashion to the Datalogger, except in this case only one analog input is read.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Pay attention to the line that reads the analog input value. It uses a Map function to change the range of the input from 0 to 1023 to a range of 0 to 180, which is what the servo requires.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">We then send this value to the servo motor to position it. A small time delay is added to allow the servo to move into place and settle.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Lastly we write the same value to the file on the SD card. \u00a0It is also pointed to the serial monitor so you can observe it in action.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Then we repeat the Loop again.<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-5654\" src=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/sd-record-servo-motor.jpg?resize=750%2C422&#038;ssl=1\" alt=\"SD Servo Motor Position Recorder\" width=\"750\" height=\"422\" srcset=\"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/sd-record-servo-motor.jpg?w=768&amp;ssl=1 768w, https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/sd-record-servo-motor.jpg?resize=300%2C169&amp;ssl=1 300w\" sizes=\"(max-width: 750px) 100vw, 750px\" data-recalc-dims=\"1\" \/><\/p>\n<p><span style=\"font-weight: 400;\">Run the sketch and put your servo through its paces. \u00a0Then stop it and move on to the next sketch, the one that will play back the motions you just recorded.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Servo Playback<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">The servo playback sketch will read the file we created and playback the servo motor movements.<\/span><\/p>\n<pre class=\"lang:default decode:true \" title=\"Servo Playback\">\/*\r\n  Servo position playback\r\n  servo-playback.ino\r\n  Plays back servo movements from SD card\r\n  Used with servo-record.ino\r\n  Displays results on Serial Monitor\r\n  DroneBot Workshop 2019\r\n  <blockquote class=\"wp-embedded-content\" data-secret=\"C5cooh158w\"><a href=\"https:\/\/dronebotworkshop.com\/\">Welcome to the Workshop!<\/a><\/blockquote><iframe class=\"wp-embedded-content\" sandbox=\"allow-scripts\" security=\"restricted\" style=\"position: absolute; clip: rect(1px, 1px, 1px, 1px);\" title=\"&#8220;Welcome to the Workshop!&#8221; &#8212; DroneBot Workshop\" src=\"https:\/\/dronebotworkshop.com\/embed\/#?secret=UAZlaXzhGU#?secret=C5cooh158w\" data-secret=\"C5cooh158w\" width=\"600\" height=\"338\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\"><\/iframe>\r\n*\/\r\n\r\n\/\/ Include libraries\r\n\r\n#include &lt;SPI.h&gt;\r\n#include &lt;SD.h&gt;\r\n#include &lt;Servo.h&gt;\r\n\r\n\/\/ CS pin for SD Card Module\r\nconst int chipSelect = 4;\r\n\r\n\/\/ String to hold one line of text\r\nString buffer;\r\n  \r\n\/\/ Create a Servo object\r\nServo myservo;\r\n\r\nvoid setup() {\r\n\r\n  \/\/ Open serial communications and wait for port to open:\r\n  Serial.begin(9600);\r\n  while (!Serial) {\r\n    ; \/\/ wait for serial port to connect. Needed for native USB port only\r\n  }\r\n\r\n  Serial.print(\"Initializing SD card...\");\r\n\r\n  \/\/ see if the card is present and can be initialized:\r\n  if (!SD.begin(chipSelect)) {\r\n    Serial.println(\"Card failed, or not present\");\r\n    \/\/ don't do anything more:\r\n    while (1);\r\n  }\r\n  Serial.println(\"card initialized.\");\r\n  \r\n  \/\/ Attach servo on pin 9 to the servo object\r\n  myservo.attach(9);  \r\n\r\n  \/\/ open the file. note that only one file can be open at a time,\r\n  \/\/ so you have to close this one before opening another.\r\n  File dataFile = SD.open(\"servopos.txt\");\r\n  \r\n \r\n  \/\/ If the file is available, read it\r\n  if (dataFile) {\r\n    while (dataFile.available()) {\r\n    \/\/ Write one line to buffer\r\n    buffer = dataFile.readStringUntil('\\n');\r\n    \/\/ Print to serial monitor\r\n      Serial.println(buffer);\r\n    \/\/ Convert string to integer and position servo\r\n      myservo.write(buffer.toInt());\r\n    delay(15); \r\n      \r\n    }\r\n    dataFile.close();\r\n  }\r\n  \/\/ if the file isn't open, pop up an error:\r\n  else {\r\n    Serial.println(\"error opening servopos.txt\");\r\n  }\r\n}\r\n\r\nvoid loop() {\r\n}\r\n<\/pre>\n<p><span style=\"font-weight: 400;\">The sketch starts identically to the previous one with the addition of a string variable called buffer. This variable will hold one line of text from the file.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">All of the action for this sketch is contained in the Setup routine, so the sketch will run once and move the motor and then it will stop. If you wish you can move some of the sketch into the loop so that the servo repeats the recorded motions indefinitely.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The file is opened for reading and then it is read, one line at a time. We accomplish this in the line <\/span><i><span style=\"font-weight: 400;\">buffer = dataFile.readStringUntil(&#8216;\\n&#8217;<\/span><\/i><span style=\"font-weight: 400;\">) . \u00a0\u00a0This will read the file until it encounters a NewLine character, which is inserted into the file after each line. <\/span><\/p>\n<p><span style=\"font-weight: 400;\">We then print the line value to the serial monitor.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">After that we use the value to set the servo motor position. Note that since the line is a string we need to convert it to an integer so that the servo object can use it. The <\/span><i><span style=\"font-weight: 400;\">toInt()<\/span><\/i><span style=\"font-weight: 400;\"> parameter accomplishes this for us.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Once again we delay the servo after each reading to give it a chance to move into position.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">We then close the file.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Run this and observe the servo motor motion, it should be identical to the motion you initially recorded.<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">Conclusion<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">As you can see it is very simple to incorporate SD cards and microSD cards into your Arduino designs. By using them you can add a huge amount of non-volatile storage to your projects.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Hopefully this has inspired you to start using these versatile devices yourself and make some beautiful memories of your own!<\/span><\/p>\n<p>&nbsp;<\/p>\n<div class=\"dbwspartsbox\">\n<h3>Parts List<\/h3>\n<p><em>Here are some components that you might need to complete the experiments in this article. Please note that some of these links may be affiliate links, and the DroneBot Workshop may receive a commission on your purchases. This does not increase the cost to you and is a method of supporting this ad-free website.<\/em><\/p>\n<p>COMING SOON!<\/p>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"dbwsresourcebox\">\n<h3><span style=\"font-weight: 400;\">Resources<\/span><\/h3>\n<p><span style=\"font-weight: 400;\"><a href=\"https:\/\/s3.amazonaws.com\/download.dronebotworkshop.com\/SD+Servo+Record+Play+DroneBot+Workshop.zip\" target=\"_blank\" rel=\"noopener noreferrer\">Code from this article<\/a> &#8211; The record and playback code, inconvenient ZIP file.<\/span><\/p>\n<p><a href=\"https:\/\/www.sdcard.org\/index.html\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"font-weight: 400;\">SD Association<\/span><\/a><span style=\"font-weight: 400;\"> &#8211; The SD Association, the people who set the standards for SD cards and all of their derivative form factors.<\/span><\/p>\n<\/div>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>SD and microSD cards are a simple way to add huge amounts of non-volatile storage to your Arduino designs. In this article, I will show you how to use SD card modules with the Arduino.<\/p>\n<p> I will also show you how to record and playback the motion of a servo motor.<\/p>\n","protected":false},"author":1,"featured_media":5651,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[9,90],"tags":[45,44],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"https:\/\/i0.wp.com\/dronebotworkshop.com\/wp-content\/uploads\/2019\/03\/SD-Cards-With-Arduino.jpeg?fit=768%2C432&ssl=1","jetpack_shortlink":"https:\/\/wp.me\/p74ClK-1sZ","jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/posts\/5641"}],"collection":[{"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/comments?post=5641"}],"version-history":[{"count":2,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/posts\/5641\/revisions"}],"predecessor-version":[{"id":9941,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/posts\/5641\/revisions\/9941"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/media\/5651"}],"wp:attachment":[{"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/media?parent=5641"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/categories?post=5641"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dronebotworkshop.com\/wp-json\/wp\/v2\/tags?post=5641"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}