I'm currently using VHDL to program the FPGA Spartan 3AN Kit-set. The objective is create a programme to send an SMS to a mobile phone, using the Kit-set via the modem. I'm done with the transmit finite-state-machine (FSM) and started doing for the receive part. However, I'm only required to send an SMS and the only thing to receive is the 'OK', which is send by the modem back to the device, after sending it an AT Command.

The question here is:

  1. Is receiving the 'OK' from the modem important?
  2. Can I substitute with delays in between each AT-Commands, assuming the modem is functioning perfectly?

Thanks in advance!


Yes, you can use a delay and ignore the response, but if it is a response to sending the actual SMS itself, then that could take some time. You would have to send several SMS messages by hand to judge how long it might take the OK to come back, and then add on some margin to the longest delay seen.

It would be much better to actually look for the OK response rather than use a delay. Two reasons: you might very likely get an ERROR or other response, instead of the OK, if the message could not be sent for some reason. Secondly, looking for the OK response saves the guesswork over how long to safely make the delay. It will allow the process, on average, to run much faster.

  • 2
    \$\begingroup\$ Fully agree - since you will be dependent on the mobile network you will want to be able to trap any ERROR reponses if the message is critical. \$\endgroup\$ – RJR Oct 30 '14 at 6:59

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