iam using SIM300S_V6.01 module,in that iam using serial port 1 all signals.iam trying to send AT commands to the module.but it is not sending any response to that particular commands.pls hep me regarding this issue.
Can you provide more details on what you are sending? What platform (PC or microcontroller)? How do you know the module is receving the data - have you verified with a scope?
the AT commands are sended through 16-bit uc via CPLD.iam sending the command only AT to GSM.this signal is seen through the scope.but iam not getting the response from the module.the pk-pk voltage is 3.3Vmax.in idle state the TXD signal is high(3.3V approx).SIM300 module supply is approx of 4.2V.
when i send Reset signal the module is turned on.this can be verified by SIM_CLK signal and SIM_VDD 2.9V generation.
When you say "Reset" signal, do you mean the "PWRKEY" pin? The "VDD_EXT " pin will go high when the module has powered-up. Also the "Network LED" pin should start toggling.