Hello,

I can communicate to my slave device locally (using serial RS232) and remotely (using GSM Wavecom modem) by sending Modbus Read Holding Register (0x03) request, and get response from the device.

If I send Write Multiple Register (0x10) request locally via serial RS232, the slave device responds. But if I send Write Multiple Register request via GSM Wavecom modem, I don't get any response from the slave device. Why does this happen? I have adjusted the timeout longer to fetch the response, but still I get no response. Pls help.

Thanks,
Dan

 

Does your modem support function 16? It might be easier to answer this question if you can provide a URL to the documentation for the model of modem you are using.

 

Hi Griffin,

I have solved the problem. I change the AT command +CBST=0,0,0 to be +CBST=0,0,1

I use Wavecom modem Fastrack Supreme.

 

Hi Griffin,

I tried the same with GenPro2Oe from ErcoGener and it works fine.

Best regards,