I am trying to use SIM900A With STM32F1 USING UART FOR SENDING MESSAGE.I CAN SEE MY TRANSMITTING DATA THROUGH PUTTY BUT IN RECEIVE BUFFER I CANT GET ANY VALUE SOMETIMES MY TRANSMITTING DATA I CAN SEE IN MY RX.WHAT SHOULD WE DO FOR SENDING MESSAGE CAN ANYONE HELP.I ALREADY CHECKED WITH USB TTL ALL COMMANDS RUNNING OK BUT FOR SENDING MESSAGE IT SHOWS ME ERROR SOMETIMES .SOMETIMES IT GOES TO MESSAGE MODE BUT MESSAGE IS NOT SENDING BUT IN STM32 I CANT GET OK RESPONSE ATLEAST FROM GSM MODULE AFTER AT COMMQAND.
THANKS IN ADVANCE
then how did you intend to test & debug this?
But, anyhow, the "hints on debugging serial comms" link given above doesn't rely on a scope or analyser...