Pogo pins power clarification - reading schematics
(01-07-2021, 07:36 PM)bokomaru Wrote: Some things to notice:
- If a "charging brick" is connected to the USB C port, the voltages at both PIN5 and PIN1 seem to be directly determined by the voltage of the USB C port supply.
- If a "charging brick" is not connected to the USB C port, the voltage at PIN1 is the battery voltage.
- If the phone is powered on, my "hacked together" variable supply (fake "brick") doesn't affect PIN1's voltage. PIN1 remains at the battery's voltage.
On (3): That's pretty strange, no? There must be something else I need to do to convince the phone that I'm a charger. But this also makes me see it your way, doubting if PIN1/DCIN is connected to the USB C port like the schematics say.
In any case, it's pretty clear to me that the wiki's statement "the second power pin is VBAT, which connects to the battery voltage" is inaccurate, or at best is an incomplete description of PIN1.
(01-07-2021, 08:22 AM)scholbert Wrote: If i should power the single board, i would design a 4.0V Power supply and attach it to the battery pins!
Unfortunately, an actual battery is actually necessary for the short bursts of high current draw from the modem, apparently on the order of Amps. So your solution to that problem would work to power part of the system, but not all. Properly powering an isolated mainboard requires a battery-like device, plus another power source for powering the phone + charging the battery. I don't see a way around it.
(01-07-2021, 08:22 AM)scholbert Wrote: Only written words so far, so maybe in the end they found out that the Pogo Pins could not be used for that.
Maybe, but I hope not true! The blog says these have gone into production already. You'd think it works.
(01-07-2021, 08:22 AM)scholbert Wrote: If they connect the "real" Qi-Charger to Pin5 (wiki name VBUS), then this would be the pin to power the boards... obviously
Ahaha, too bad that's the opposite conclusion of how I read the schematics. I feel like we still have no idea which pin would be the charging input or why.
We've definitely made some progress though :-)
O.K. try to keep it a little shorter this time.
The PMIC components on modern platforms are complex logic.
Intense reading of the datasheet may be helpful... or compare it with another reference design:
https://files.pine64.org/doc/Pine%20A64%...elease.pdf
Anyway, it would be a solution to pull to phone apart and use a logic tester to find out where the pins are connected to.
Another thing i realized by having a closer look at the schematic again (and a comparison with the Pine A64+ schematic as well).
It seems to me that there are two different DCIN nets with barely the same name... see my screenshots attached.
My next guess is there could be net names like "DCIN" and "DCIN ".
The red circles may point the same nets then... hope you know what i mean.
BTW, i missed U102 (load switch)... and you're completely right this component would block a direct measurement.
So agreed with most of the things you mentioned...
Some last note concerning your comment on the power supply... you're right to point at the current pulses drawn by the modem.
All you would need here, are some additional decoupling caps with a proper capacity (see the EG25 hardware guides as a reference as well).
The caps on the pinephone mainboard (modem section) are barely sufficient in that case.
Anyway... we're not discussing to build up a DCDC supply for the phone... so good point!!
I enjoy this conversation, but to get clearness we need some reverse engineering... or definite information from the Pine64 team!
Regards,
scholbert
