Reading from Encased SD Breakout through COM Port

Projects Interfacing w/ Software on the Computer
1

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.

2

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.

3

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()?

4

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.