PocketBeagle Power Problems

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Paul Beam

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May 19, 2020, 6:02:21 PM5/19/20
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I have been trying to work through some PocketBeagle power weirdness.  I have an external battery backed supply which outputs 5V.  If I route power into Vin (P1.1) I run into problems with glitches from my power supply when I plug or unplug a USB charger.  The worst problem seems to be that VBAT gets a charge on it so that PocketBeagble won't start until I temporarily short VBAT to ground.  The other problem I get is sometimes the PocketBeagle will reboot.  My PS may not be perfect, but I have not been able to find on the scope anything that explains this.

So, I moved my power input over to VBAT.  I no longer have rebooting issues nor any problems unplugging or plugging the charger.  But, all the 3.3V and Vout pins are still powered when the PocketBeagle is "Off."  VIN-USB (P1.7) seems to turn on and off with the PB power LED.  Vout (P1.14) stays at 5V regardless of whether the PB is on or off, which means my connected circuitry stays on and drains power when things should be off.

From what I can tell, VIN seems to have a different brownout threshold than VBAT, but I have no explanation for VOUT being on continuously when VBAT is applied.  

Thoughts?

Pablo Rodriguez

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May 19, 2020, 8:00:46 PM5/19/20
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Vin on same pocket Beagle is bugged, havent seen any official statement but all My pb( like 6) have the same random reset when powered by Vin. Not when powered from vusb with the same power supply.
Good luck

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Stuart Longland

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May 19, 2020, 8:07:48 PM5/19/20
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On 20/5/20 10:00 am, Pablo Rodriguez wrote:
> Vin on same pocket Beagle is bugged, havent seen any official statement but
> all My pb( like 6) have the same random reset when powered by Vin. Not when
> powered from vusb with the same power supply.
> Good luck

Are these recently purchased boards that are suffering glitches? We've
got a fleet of 6 which have been running fine from Vin. Maybe some bulk
capacitance might help?
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Stuart Longland (aka Redhatter, VK4MSL)

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Paul Beam

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May 19, 2020, 8:32:27 PM5/19/20
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Very recent PB’s.  My power supply is a combo li ion battery and TI charge boost converter which does glitch when switching from usb input to battery.  The bigger problem is when it won’t power on till I bleed the voltage from Vbat.  I have not seen this glitch mentioned anywhere.  I have found it possible to get a voltage on an unconnected VBat and the PB will not start.   

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Paul Beam

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May 20, 2020, 2:49:30 PM5/20/20
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There is something wonky with VIN_AC.  If you physically remove power, then things seem fine, but using PB for off and on can lead to a state where it won't turn on.  USB1_VIN works better for some reason.

Does anyone know how to read/change PMIC registers after Linux has loaded?  i2ctools does not work since the kernel has the device.  

er...@take4.dk

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Jun 2, 2020, 4:10:46 AM6/2/20
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I have experienced the random reset issue on 10+ PBs when using VIN_AC, so I moved to power through USB1_VIN too. That fixed the intermittent reset-issue. But periodically I’m now experiencing the issue where the device will not power up after a shutdown, when pulling the PowerButton pin low.

 

Did anyone find a solution for this?

 

VOUT and VBAT are both showing 1.09 V in this situation (they are not connected to any circuitry.

 

Best regards,

 

Erik

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Paul Beam

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Aug 16, 2020, 6:02:08 PM8/16/20
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I have fought this same problem, thought it was resolved, and found it again.  I think the authoritative answer is in this TI app note: https://www.ti.com/lit/an/slva901/slva901.pdf?ts=1597613555964&ref_url=https%253A%252F%252Fwww.google.com%252F

Cutting to the chase, either ground the BAT terminal with  1K-ish resistor or power your product exclusively through the BAT terminal.  In my case, I tried to use both Vin and VUSB with an external battery and charger, plugging and unplugging the charger would cause a brief brownout condition that would lock up the PMIC and require the power to be removed before you could turn it on again.  According to the TI doc, the PMIC was really designed for battery as the primary power source, so not having a battery plugged in leads to some imperfect results -- like not being able to turn the stupid thing on.  I'm now just using BAT and things appear to work.
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