SOPine modules stay off at reboot?

[Pine]

Hi all, I'm desperately working on this issue too in 2021. It's so perplexing, so much so that I've taken to document my long investigation into this: https://ericdraken.com/a64-reset-problem/

First of all, thank you very much for writing such an extensive article!  It must have required a whole lot of elbow grease and many sleepless nights.

Your article concludes that two AA batteries in a powered-on Clusterboard will become dead in about a couple of months, as a result of the power draw from batteries being much higher when the Clusterboard is powered on.  Obviously, discharging batteries while the system is taking power from the wall makes very little sense, so I followed along and researched the relevant parts of the Clusterboard, SOPine, SOPine Baseboard and Pine A64-LTS schematic.  Below are some of my conclusions.

You've also raised a question about the missing OD4 diode in the SOPine schematic, and you've actually confirmed that the OD4 is physically present on the SOPine module.  Moreover, a complete translation of a mixed-language note in the SOPine schematic, near the circled OD4, is as follows:

Note: R9717 DELETE increases OD4

I'm not sure where the R9717 exactly is; there's one on the SOPine Baseboard, but it isn't marked as NC.  Though, it's also circled in the SOPine Baseboard schematic and labeled as "debug", so it's probably the right R9717.  Anyway, this just additionally confirms that the OD4 is populated.

Furthermore, if I'm not wrong, there's nothing that can stop the combined VCC_RTC outputs of the AXP803 PMICs on all seven SOPine modules to attempt charging the two AA batteries?  It would get even worse once the batteries become weak, so they can no longer "fight" against the VCC_RTC outputs.  Am I wrong there?

Thank you, my friend.

Since I found the diode, I've added about 20% more to that page I made. I tried to model the schematic as well. One discovery I made is that PWROK drops to 2.25V without the RTC battery, but stays at 3.25V (+0.25V due to voltage from the 74LVT04) with an RTC battery. In the baseboard, PWROK stays at 3.00V, of course (no 74LVT04).



About the RTC battery fighting a losing battle, it looks to power all 7 SOPines, yes, then gets weaker, and then gets overpowered by the combined VCC_RTC output of the 7 SOPines. The baseboard solves this with diode OD3. I'll opt to not use batteries going forward.

I've ordered some custom hardware from Ali to edit the PCB trace lines to test fix ideas.