The Metro RP2040 has an onboard SD card slot, making it easy to read and write files from a micro SD card. To do this with Arduino, you'll need to plug in your micro SD card, install the Adafruit fork of the SdFat library and run the provided example code.
Library Installation
You can install the Adafruit Fork of the SDFat library for Arduino using the Library Manager in the Arduino IDE.
Click the Manage Libraries ... menu item, search for Adafruit SDFat and select the SDFat - Adafruit Fork library:
// SPDX-FileCopyrightText: 2023 Liz Clark for Adafruit Industries // // SPDX-License-Identifier: MIT /* SD card read/write This example shows how to read and write data to and from an SD card file The circuit: * SD card attached to SPI0 bus as follows: ** MOSI - pin 19 ** MISO - pin 20 ** CLK - pin 18 created Nov 2010 by David A. Mellis modified 9 Apr 2012 by Tom Igoe modified 14 Feb 2023 by Liz Clark This example code is in the public domain. */ #include "SdFat.h" SdFat sd; #define SD_FAT_TYPE 1 // default CS pin is 23 for Metro RP2040 #define SD_CS_PIN 23 File32 myFile; void setup() { // Open serial communications and wait for port to open: Serial.begin(115200); while (!Serial) { ; // wait for serial port to connect. Needed for native USB port only } Serial.print("Initializing SD card..."); if (!sd.begin(SD_CS_PIN)) { Serial.println("initialization failed!"); return; } Serial.println("initialization done."); // open the file. note that only one file can be open at a time, // so you have to close this one before opening another. myFile.open("test.txt", FILE_WRITE); // if the file opened okay, write to it: if (myFile) { Serial.print("Writing to test.txt..."); myFile.println("testing 1, 2, 3."); myFile.println("hello metro rp2040!"); // close the file: myFile.close(); Serial.println("done."); } else { // if the file didn't open, print an error: Serial.println("error opening test.txt"); } // re-open the file for reading: myFile.open("test.txt"); if (myFile) { Serial.println("test.txt:"); // read from the file until there's nothing else in it: while (myFile.available()) { Serial.write(myFile.read()); } // close the file: myFile.close(); } else { // if the file didn't open, print an error: Serial.println("error opening test.txt"); } } void loop() { // nothing happens after setup }
Upload the sketch to your board and open up the Serial Monitor (Tools -> Serial Monitor) at 115200 baud. A test text file will be created and written to on the SD card. Then, the text file will be read back with its contents printed to the Serial Monitor.
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