TCP Connection Failure - even after Detatch/Attach (never appeared to get back on the network)

We recently ran into an issue with poor connectivity where the module never was able to establish a TCP Connection.

Interesting observations:

  • HL8548 reported it was attached. Our SIM Portal said otherwise (did not attach for 24 hours as we made sure it could not get signal)
  • RSSI Readings appeared valid (did not verify it changed at all)
  • Calling Detach and then Attach again resulted in a successful attach response. Again, the SIM portal did not indicate the radio ever attached since the last time over 24 hours prior.
  • TCP Connection still failed

The only way to recover at that point was to hard reset the module.

This seems like a bug in the HL8548 running the RHL85xx. version of the firmware that it lost its mind with regards to connection.


Is this just an observation and posting telling people or is there a question? The unit does not normally mistake its attach status because the procedure it has to complete to declare it is attached is pretty explicit.

Also which attach state are you talking about circuit (at+creg?) or packet (at+cgreg?)? Its could be the portal was showing one and you were checking the other.



The portal was showing no connection state for 24 hours (the module was placed in a RF shield so it could not attach), then removed. The Attach status of CGATT was 1 and we were getting RSSI numbers from $CSQ upon removal.

Calling CGATT=0 followed by CGATT=1 resulted in what seemed like a successful connect and valid RSSI numbers from $CSQ. However, our SIM portal showed no new authentication request or any attachment/transmissions like we would normally see.