[SOLVED] SIM900 Shield AT Error


Running the code from here: https://github.com/hologram-io/hologram-SIMCOM


ERROR: Timeout when calling AT
_ | elapsed ms = 0_
ERROR: begin() failed at AT
DEBUG: Verbose monitoring and modem serial access enabled
DEBUG: Write Modem Serial = AT+CGATT?
ERROR: Timeout when calling AT+CGATT?
| elapsed ms = 0
DEBUG: Write Modem Serial = AT+CGATT?

I’m sure I connected it wrong, diagram below:


If the first AT command fails it means the Uno cannot talk with the modem. Make sure the TX & RX are right. Remember the modem’s TX > Uno RX & modem RX > Uno TX. You’ll need to know the shield’s pinout.


Got it working, for those running the same board:

Make sure for data transmission between the sim900 and arduino using pins 7,8 make sure that the jumper of the GSM card is positioned in D7 and D8 to activate these pins.