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3

You only need to open the file with FILE_WRITE and use file.seek(EOF) to go to de end of the file. After that you can write whatever you want that will be appended to the end of the file. File outputFile = SD.open(LOG_FILE, FILE_WRITE); outputFile.seek(EOF); outputFile.println("Appended to the EOF");


2

Unfortunately the DFPlayer cant write that data to the SD card. The Arduino has some non volatile memory of its own built in though. Theres 1K of EEPROM for the UNO. Notes on how to use it here: https://www.arduino.cc/en/Reference/EEPROM If you can get what you need to done in 1K and its not important to your project that you be able to unplug the SD card ...


2

Not with an ATTiny85, and not with so few pins, no. However, all is not lost. The ATTint85 has 512 bytes of EEPROM inside it where you can store your login details. All you need is some way of telling setting that data in your sketch from the PC - and the simplest way is probably through a USB serial connection. If you don't have a serial connection ...


1

Ok i found the solution. It was not too complicated. I just assumed the problem was in the code. This works well enough (dont ask me about the counter--) unsigned short EKG_recording::count_files_from_SD() { root = SD.open("/"); root.rewindDirectory(); //Sets to beginning of directory while (true) { File entry = root.openNextFile(); if(!...


1

SD cards work with SPI. This needs only one pin per device (SlaveSelect) but 3 pins for the other common signals ( MISO / MOSI / SCK ) Card reader modules simply do some voltage level shifting (if at all). But, you need a lot of RAM to work with SD cards, as data transfer always happens in 512 byte "sectors". With a file system, you need at least two such ...


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You can use the adapter because: the adapter uses an AMS1117 to generate 3.3V to supply the SD card and the level shifter the level shifter is a 74LVC125 which uses 3.3V and works with 3.3V (and accepts up to 5V as input level) The adapter works for 3.3V and 5V systems as long as 5V power is available.


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