sim900 initialization problem

[tuan_vu]

Hello,
I am currently working on a project with GSM module SIM900. I connect this module with Altera DE to send command and read data. I build a Nios system with UART core. Everything is quite good, but I still have a problem. After I power up this module, if I use DE board to send the first command to module, there isn't any response for any commands. However, if I use PC to send the first command, the module responses, after that, I connect DE with SIM900 and my code run fluently, I can send commands and read messages. Do you have any idea with my problem? Thank you!!!

 

[artofcircuits]

Hi Tuan,

Please make sure your code running on Altera DE board sends out Carriage Return character ("\r" or 0x0D) after every line of command sent to SIM900 modem. The modems expect all commands be terminated by a carriage return character.

Let me know if you still have problem after adding carriage return character is added to terminate command string.

Kind Regards

 

[tuan_vu]

Hi Tuan,

Please make sure your code running on Altera DE board sends out Carriage Return character ("\r" or 0x0D) after every line of command sent to SIM900 modem. The modems expect all commands be terminated by a carriage return character.

Let me know if you still have problem after adding carriage return character is added to terminate command string.

Kind Regards

thanks for your reply,
my code has <CR> character after every command. After I send first command by PC, DE board and SIM900 module communicates fluently, Module can receive to send sms, and board can receive the responses. I guess that PC firstly send some signal to initialize module. However, I cann't find any information about that.