I use stm32f107，now I want to communicate with a 2G gprs module by usb。How I do it ？
Not likely to be super practical. Consider using a RPi for USB connectivity, or find a serial (USART) connectable Cellular Modem
Just out of curiosity: what makes you use the USB for GPRS module?
AT commands through the UART are the simplest and popular way of communicating with GSM modems. I used binary protocols for this purpose once (i.e. Nokia FBUS protocol) but it complicates things. I did it because I had a few decent Nokia phones and wanted to use them for the purpose.
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