FCDEV3B hardware bug: sleep mode self-reboot

[Das Signal]

By the way, I've noticed something interesting:  if I wait until AT+CFUN=1
receives ATI: OK, and then issue AT%SLEEP=0 then AT+COPS=0, it appears the
board can successfully register without rebooting. If I'm not wrong, after
AT+CFUN=1 the board starts talking to the (U)SIM card, which could perhaps
be a culprit for the observed behaviour wrt/ sleeping.

On Sat, Jul 29, 2017 at 11:33:17AM +0000, Das Signal wrote:
> Hi Mychaela,
> 
> Thank you for the detailed indications. I have first recompiled magnetite
> in the l1reconst configuration and flashed it. I can confirm that issuing
> the AT+CFUN=1 command through fc-shell does cause a reboot of the board
> (and does not cause one with AT%SLEEP=2 issued before).
> 
> I had no problem identifying the three caps, and indeed the voltage is
> at 1.5V which is expected. In the three cases, I have issued the AT+CFUN
> command while observing the output on the scope. There was no voltage drop,
> however there was some slight "noise", which is to say the voltage varied
> a little bit around 1.5V (at most +/- 0.1V). However this could be due to
> the power draw when the board was rebooting, as this noise appears much
> after the AT command. Please have a look at the oscilloscope screenshot
> that illustrates the situation:
> https://www.freecalypso.org/members/ds/NewFile1.png
> 
> I've noted that the radio part of the board does not seems turned on
> until after AT+COPS=0 is issued; hence the possibility that the RF part
> is not (at least directly) responsible for this situation (RF TX would
> likely be the most power hungry part of the board).
> 
> --DS
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