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. 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!!!

 

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I'd verify that the PC (software) isn't sending some initialization sequence to the module, which you probably aren't doing with your Altera design.