Sending AT commands to a GSM

[Aaron Graves]

Hello All, I am working with a pre-programed PCB; the main components of the are a nRF51822 chip, a GPS, and a GSM. I am using a J-link to communicate to the entire board through the SWD (SWDIO and SWDCLK) pins on the nRF51. I need to send AT commands to the GSM to test it for functionality. How do I do that? I have been told that I need to embed the AT commands in the nRF51's source code and re-flash it to the chip. However, I do not have the original source code. Is there any way to have the nRF51 send the GSM the AT commands without re-flashing the the source code? I would like to send the AT commands using serial (using a Putty or the like). Can this be done through the SWD pins? Thanks.

[Hung Bui]

@Aaron: if you have access to the SWD interface and if the firmware on the nRF51 chip is not read back protected. You can simply readout the chip's image, store it. Then make your own firmware to test the GSM chip. After you have done that you can flash the original image back.

Or you can simply don't power the nRF51 chip, and hook the UART lines from PC to the UART pins on the GSM chip. And can try to control it from the PC. This would require some hardware hack on the board.

Or you can try what Ulrich suggested.