CristianM
Posts: 4
Joined: Thu Mar 15, 2018 7:14 pm

Troubleshoot PMIC

Tue May 15, 2018 6:48 am

Hello! I have a faulty RPI3 B+. I think the problem is caused by the PMIC. I measured 5V at the inputs of the chip (pins 24, 31), but no 3V3 output.

Is there anything else I can do to repair the RPI? Or should I replace the PMIC (if so, what version is it MxL7704 AQB or XQB)?

deNiro
Posts: 1
Joined: Thu May 24, 2018 6:47 pm

Re: Troubleshoot PMIC

Fri May 25, 2018 4:20 pm

I accidentally made a short 5V rail to 3.3V what resulted in having 3.3V power rail down.
I've replaced PMIC with MxL7704 AQB (powering sequence in this option looks reasonable) and installed the system. System got installed alright but low voltage warning comes up when it's booting up and power flag is constantly on. Also, I have a feeling that VDD_core=1.3V is a bit too high. However, I don't know what was a level of that voltage before the failure and I struggle to find a detailed specification of BCM2837B0.
System seems stable, however I haven't run any benchmarks yet.
I hope this helps

hardy8
Posts: 5
Joined: Wed Apr 03, 2019 8:32 am

Re: Troubleshoot PMIC

Wed Apr 03, 2019 8:49 am

I have got the same problem, shorted 5v to Gnd. Now no voltage on 3v3 pin on pi 3 b+ . My PMIC is blown and before replacing the PMIC, I want to know the configuration of all the register in MxL7704 IC used in a brand new pi 3 b+. I think new PMIC registers should be configured same as in registers of a PMIC in brand new pi 3b+. It would be great help if somebody on this forum could help to share the configuration. This configuration can be read using I2c interface of PMIC on pin numbers 2 and 3 of MxL7704. Some micro-controller as Arduino could be used to do this task. As this is an open source hardware. The configuration of this IC should be shared by Raspberry.org too. However, I could hardly find these value of PMIC registers. It would be great help if somebody can provide me these values to recover my pi 3 b+ .

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mahjongg
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Re: Troubleshoot PMIC

Wed Apr 03, 2019 8:52 am

hardy8 wrote:
Wed Apr 03, 2019 8:49 am
As this is an open source hardware. The configuration of this IC should be shared by Raspberry.org too.
I don't know where you got that notion from, but the RPI is NOT open source hardware!!!!

hardy8
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Re: Troubleshoot PMIC

Wed Apr 03, 2019 11:56 am

mahjongg wrote:
Wed Apr 03, 2019 8:52 am
hardy8 wrote:
Wed Apr 03, 2019 8:49 am
As this is an open source hardware. The configuration of this IC should be shared by Raspberry.org too.
I don't know where you got that notion from, but the RPI is NOT open source hardware!!!!
That is real bug. :shock:

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B.Goode
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Re: Troubleshoot PMIC

Wed Apr 03, 2019 12:06 pm

hardy8 wrote:
Wed Apr 03, 2019 11:56 am
mahjongg wrote:
Wed Apr 03, 2019 8:52 am
hardy8 wrote:
Wed Apr 03, 2019 8:49 am
As this is an open source hardware. The configuration of this IC should be shared by Raspberry.org too.
I don't know where you got that notion from, but the RPI is NOT open source hardware!!!!
That is real bug. :shock:

Fortunately you have the option of not buying hardware that you consider to be "buggy."

You could build your own version that does not have that deficiency.

jamesh
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Re: Troubleshoot PMIC

Wed Apr 03, 2019 2:06 pm

hardy8 wrote:
Wed Apr 03, 2019 11:56 am
mahjongg wrote:
Wed Apr 03, 2019 8:52 am
hardy8 wrote:
Wed Apr 03, 2019 8:49 am
As this is an open source hardware. The configuration of this IC should be shared by Raspberry.org too.
I don't know where you got that notion from, but the RPI is NOT open source hardware!!!!
That is real bug. :shock:
Been there a long time, without anyone spotting it...!!!
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hardy8
Posts: 5
Joined: Wed Apr 03, 2019 8:32 am

Re: Troubleshoot PMIC

Sun Apr 07, 2019 6:57 am

It would be great help if anyone could share that PMIC registers' values for a new pi 3b+. I think replacing PMIC with these values could give a new life to my pi :idea:

krishna72
Posts: 3
Joined: Sun Apr 07, 2019 9:07 am

Re: Troubleshoot PMIC

Mon Sep 16, 2019 11:50 am

hardy8 wrote:
Wed Apr 03, 2019 8:49 am
I have got the same problem, shorted 5v to Gnd. Now no voltage on 3v3 pin on pi 3 b+ . My PMIC is blown and before replacing the PMIC, I want to know the configuration of all the register in MxL7704 IC used in a brand new pi 3 b+. I think new PMIC registers should be configured same as in registers of a PMIC in brand new pi 3b+. It would be great help if somebody on this forum could help to share the configuration. This configuration can be read using I2c interface of PMIC on pin numbers 2 and 3 of MxL7704. Some micro-controller as Arduino could be used to do this task. As this is an open source hardware. The configuration of this IC should be shared by Raspberry.org too. However, I could hardly find these value of PMIC registers. It would be great help if somebody can provide me these values to recover my pi 3 b+ .
How did you conclude your pmic is blown?
Have you tried I2C interface connection with PMIC(what ,you thought to be burnt)?
I too have similar problem with my RPi3B+. But, pmic has no signs of burning/melting and was not HOT while I shorted 3v3 pin and killed my RPi (but my 32GB samsung sdcard damaged).
Seems to be some dead lock occured with firmware in it.
Last edited by krishna72 on Mon Sep 16, 2019 12:00 pm, edited 1 time in total.

krishna72
Posts: 3
Joined: Sun Apr 07, 2019 9:07 am

Re: Troubleshoot PMIC

Mon Sep 16, 2019 11:59 am

deNiro wrote:
Fri May 25, 2018 4:20 pm
I accidentally made a short 5V rail to 3.3V what resulted in having 3.3V power rail down.
I've replaced PMIC with MxL7704 AQB (powering sequence in this option looks reasonable) and installed the system. System got installed alright but low voltage warning comes up when it's booting up and power flag is constantly on. Also, I have a feeling that VDD_core=1.3V is a bit too high. However, I don't know what was a level of that voltage before the failure and I struggle to find a detailed specification of BCM2837B0.
System seems stable, however I haven't run any benchmarks yet.
I hope this helps
Didn't replacing PMIC ,cost atleast half the cost of RPi?

Andyroo

Re: Troubleshoot PMIC

Mon Sep 16, 2019 12:02 pm

The OP has not been here since February this year so it’s unlikely you will get an answer.

Please check the date of posts as lots could have changed in the meantime and you can see if the poster is active by clicking on their name and that will show the last active date.

LTolledo
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Re: Troubleshoot PMIC

Mon Sep 16, 2019 1:51 pm

looks cheap but more expensive (in a lot of ways) and troublesome in the long run!

give it up!
get a new one and
move on!
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

hardy8
Posts: 5
Joined: Wed Apr 03, 2019 8:32 am

Re: Troubleshoot PMIC

Sun Sep 22, 2019 5:24 pm

I bought a new PMIC mxl7704 r3 from aliexpress. After mounting it to a breakout board , I tried arduino to read register value of chip. But I got no output from PMIC's i2c bus. Slave address 0x2d is written in PMIC datasheet. Can anyone suggest how to read and write data to chip.

hippy
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Location: UK

Re: Troubleshoot PMIC

Sun Sep 22, 2019 6:58 pm

Beyond the datasheet mentioning dropped ACK/NAK I would have expected it to be standard I2C. Perhaps retry if you aren't getting the expected ACK/NAK and that's causing problems.

You could try testing some other I2C device to check it's not your hardware or software which is the problem. You could put a logic analyser on the I2C bus to see what a working Pi sends to it.

Have you remembered to add pull-ups ?

hardy8
Posts: 5
Joined: Wed Apr 03, 2019 8:32 am

Re: Troubleshoot PMIC

Wed Sep 25, 2019 4:26 pm

hippy, I am using arduino pro mini 3.3v 8Mhz for i2c communication using Arduino wire library. I have added pull up of 1k to 3.3v.

Unable to get any data from new and old ICs. Arduino to arduino i2c communication works fine. Is there any special code required for Nack/Ack i2c communication ? I am using example sketch master_reader provided in arduino IDE and putting slave address as 0x2d

trejan
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Re: Troubleshoot PMIC

Wed Sep 25, 2019 4:36 pm

hardy8 wrote:
Sun Apr 07, 2019 6:57 am
It would be great help if anyone could share that PMIC registers' values for a new pi 3b+. I think replacing PMIC with these values could give a new life to my pi :idea:
Supposedly there are differences between the generic chip and Pi specific versions that aren't covered by the config registers. You can only change those options by getting a custom chip.

hippy
Posts: 6230
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: Troubleshoot PMIC

Wed Sep 25, 2019 7:07 pm

hardy8 wrote:
Wed Sep 25, 2019 4:26 pm
Is there any special code required for Nack/Ack i2c communication ?
Beyond it NAK'ing when busy, which suggests simply trying again, I have no idea I'm afraid.
hardy8 wrote:
Wed Sep 25, 2019 4:26 pm
I am using example sketch master_reader provided in arduino IDE and putting slave address as 0x2d
Try scanning all addresses. Maybe bit-bang the I2C so you can control timing and slow things down. Try General Call and 10-bit addressing.

Though the version used on a Pi is said to be proprietary the rest of the range isn't so there might be some GitHub example code which proves useful. Might also be worth searching for info on the old part number; XR77004.

There has been forum discussion of using the MxL7704 externally with the Compute Module which may provide some information. This might be useful -

https://www.raspberrypi.org/forums/view ... p?p=923243

That suggests that it's a standard I2C bus to the PMIC and other I2C chips so it cannot be too non-standard. And, given they call it "I2C".

Note it suggests the address is actually "28". Maybe that's the proprietary part ?

Perhaps post pictures of your setup and wiring. Perhaps something isn't connected how it should be.

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