Reading from Encased SD Breakout through COM Port

Hi all,

I am trying to figure out a solution to read data off an SD card storing NMEA sentences from a GPS logger attached to an Arduino Pro Micro. The Arduino writes NMEA sentences to a FAT16 text document in a directory on the SD card. The package (SD breakout, Arduino, GPS module, battery) is encased in a small plastic box and the SD card is not accessible to the user.

Ideally, I would like to attach a 3.5mm to USB cable to my project and, over serial, read (through the command prompt or a GUI) the text file(s) off of the SD card to a directory on Windows. Does anyone know of a way I can do this without having to flash a new program onto the Arduino?

I have Googled this furiously but haven't had any luck. Thank you in advance for your help.

-G

EDIT: I'm hoping I can just dump the flash similarly to this command: avrdude -c usbtiny -p atmega328p -U flash:r:mystery.hex:r Rather I'd want the contents of the SD card, not the flash memory on the microcontroller.

Does anyone know of a way I can do this without having to flash a new program onto the Arduino?

You can't. The SD card reader/writer is a dumb piece of hardware without a microcontroller around.

Since your microcontroller does not have the functionality that you want, the only solution is to add that functionality to the code and upload the new program.

Thanks Paul. Does it sound feasible to you then to include some code in the program that "listens" for a 3.5mm jack input and pushes the collected NMEA sentences line by line, file by file to that serial connection via SoftwareSerial()?

Does it sound feasible to you then to include some code in the program that “listens” for a 3.5mm jack input

No. There must be some way to connect a switch, or something useful, to the Arduino. I don’t know what you think the Arduino would be “listening” for.