FXT-009 power supply issue

Hi, all

Did anyone had issues with FXT-009 when power is removed for a short period (under 5s)?
Our system, upon successful startup attempts to make a voice call and generates some tone through audio.
If I remove power to the modem and re-apply it within about 5s, this first call starts and modem resets few seconds into the call. Absolutely no indication why this happens. nothing through debug interface to TMT, nothing in EEPROM, no exception generated. If power is disconnected for about 10s, problem is not happening.
I remove power by pulling power plug from the modem to take external power supply out of equation.

Any ideas?


Remember that the FXT has an internal switch-mode PSU, so it’s not all that surprising that this might take a short time to discharge - with the results that you describe.

I know it has internal supply, but failure mode is somewhat strange:

  1. Unit works normally otherwise, always fail in exact same manner and same place in the code.
  2. Soft reset does not clear the fault. Unit has to be unplugged for about 10s.

This failure indicates that something is not initialized properly (GSM DSP is my guess) and fault can not be recovered from. What if unit is out there unattended? Brownout can happen, but after power comes back, soft reset should should fix any issues.


We were able to reproduce the effect on Q2687h module with R7.44 firmware. Under investigation now.
Cant reproduce effect after upgrading firmware to R7.45 yet.