lornova
Posts: 4
Joined: Sun Apr 15, 2018 1:21 pm
Location: Turin

Raspberry Pi 400 replacement motherboard

Fri May 07, 2021 4:41 pm

My Pi 400 has some electrical problem: I connected an FTDI-USB module to the GND, TXD and RXD pins of the GPIO of the Pi 400, and the CP2102 chip smoked and desoldered itself from the FTDI-USB module PCB. I tried another module and it burned, too.

The Raspberry boots and seems to work, with the exception of the UART (I haven't tested other GPIO pins).

It is possible to order just a replacement mainboard for the Raspberry Pi 400? Even if the price is almost the same as the full system, I'd like to savage the keyboard/case/heatsink to avoid a bit of e-waste...
Last edited by lornova on Mon May 10, 2021 3:27 pm, edited 1 time in total.

ejolson
Posts: 7231
Joined: Tue Mar 18, 2014 11:47 am

Re: Raspberry Pi 400 replacement motherboard

Fri May 07, 2021 4:47 pm

lornova wrote:
Fri May 07, 2021 4:41 pm
I accidentally connected the 5V output of an FTDI-USB module to the TXD pin of the GPIO of the Pi 400... The CP2102 chip smoked and desoldered itself from the FTDI-USB module PCB..

The Raspberry Pi 400 kinda survived: it boots and so far seems to work, with the exception of the UART (I haven't tested other GPIO pins).

It is possible to order just a replacement mainboard for the Raspberry Pi 400? Even if the price is almost the same as the full system, I'd like to savage the keyboard/case/heatsink to avoid a bit of e-waste...
Since the Pi 400 is a consumer device (not a component like the others), it should be repairable. It's price, like a toaster, may be too cheap to fall under any proposed or enforced legislation.

Once in a while someone posts on this forum that they broke the keyboard but not the Pi inside. Maybe some sort of swap to create a single working Pi 400 could be performed next time this happens.

Where I live a rather huge two compressor refrigerator was just sent to the dump because one of the compressors ran out of gas or something. When stuff like that happens, worrying about the Pi is like trying to solve a drought by foregoing a glass of water at the restaurant.

lornova
Posts: 4
Joined: Sun Apr 15, 2018 1:21 pm
Location: Turin

Re: Raspberry Pi 400 replacement motherboard

Mon May 10, 2021 4:02 pm

Just a little update: my initial thought, that I misconnected the FTDI module, was wrong because... I cut the 3V3 and the 5V pins from the FTDI module, just to avoid that kind of mistake! In fact, it is the Raspberry Pi 400 that is outputting 5V from the GPIO pins :shock:
Pi 400 Broken GPIO.jpg
Pi 400 Broken GPIO.jpg (152.02 KiB) Viewed 1135 times

User avatar
rpdom
Posts: 18692
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: Raspberry Pi 400 replacement motherboard

Mon May 10, 2021 4:59 pm

Well, you've got that board plugged in to your Pi the wrong way round, so you're actually testing between Pin 2 (5V) and Pin 33 (GPIO 13).
I could be wrong. See next post.
Last edited by rpdom on Mon May 10, 2021 8:08 pm, edited 1 time in total.
Unreadable squiggle

aBUGSworstnightmare
Posts: 2904
Joined: Tue Jun 30, 2015 1:35 pm

Re: Raspberry Pi 400 replacement motherboard

Mon May 10, 2021 7:25 pm

rpdom wrote:
Mon May 10, 2021 4:59 pm
Well, you've got that board plugged in to your Pi the wrong way round, so you're actually testing between Pin 2 (5V) and Pin 33 (GPIO 13).
there are GPIO expansion boards out in the field which rotate the Pi400 GPIO by 180deg -> HAT would face away from the Pi. Also got fouled by such a boads picture once (viewtopic.php?f=140&t=309654) and need to say that I stop answering questions related to them. Too much confusion .. And too much risk for unexperienced folks to blow their Pi400 --> wont take that risk!

Let me repeat what I've said in a similiar thread: in case you want to use HATs the simplest solution is by this https://shop.pimoroni.com/products/spar ... rry-pi-400

Note: I'm not related to sparkfun nor pimoroni! This PCB is simply more easy to use for starters as the GPIO position is same as with every other RPi, hence all 'tutorials' starters may follow are valid.
Last edited by aBUGSworstnightmare on Wed May 12, 2021 5:03 am, edited 4 times in total.

User avatar
rpdom
Posts: 18692
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: Raspberry Pi 400 replacement motherboard

Mon May 10, 2021 8:07 pm

aBUGSworstnightmare wrote:
Mon May 10, 2021 7:25 pm
rpdom wrote:
Mon May 10, 2021 4:59 pm
Well, you've got that board plugged in to your Pi the wrong way round, so you're actually testing between Pin 2 (5V) and Pin 33 (GPIO 13).
there are GPIO expansion boards out in the field which rotate the Pi400 GPIO by 180deg -> HAT would face away from the Pi. Also bot fouled by such a boads pic again and need to say that I stop a swering questions related to them. Too much confusion .. And too much risk for unexperienced folks to blow their Pi400 --> wont take that risk!
Yes, you could be right. The tracks on that board do look like they could be switching the directions. I'll retract my earlier comment.
Unreadable squiggle

User avatar
Gavinmc42
Posts: 5631
Joined: Wed Aug 28, 2013 3:31 am

Re: Raspberry Pi 400 replacement motherboard

Tue May 11, 2021 11:21 am

Isn't that one of the two 5V pins in the normal Pi header?
Is that plugged in upside down?
No idea, just took the rubber cap off mine for the first time, some molded labels hard to read.

Page 20 of the Beginners Guide helps, might try looking again in daylight.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

drgeoff
Posts: 11910
Joined: Wed Jan 25, 2012 6:39 pm

Re: Raspberry Pi 400 replacement motherboard

Tue May 11, 2021 6:06 pm

Something not right somewhere. If the red multimeter lead is really on a ground point then the meter is showing 5 Volts negative.
Quis custodiet ipsos custodes?

cleverca22
Posts: 3739
Joined: Sat Aug 18, 2012 2:33 pm

Re: Raspberry Pi 400 replacement motherboard

Tue May 11, 2021 6:09 pm

drgeoff wrote:
Tue May 11, 2021 6:06 pm
Something not right somewhere. If the red multimeter lead is really on a ground point then the meter is showing 5 Volts negative.
yeah, now i'm even more confused!

where did that board come from?
is the meter wired up correctly?

User avatar
mahjongg
Forum Moderator
Forum Moderator
Posts: 13961
Joined: Sun Mar 11, 2012 12:19 am
Location: South Holland, The Netherlands

Re: Raspberry Pi 400 replacement motherboard

Sat May 15, 2021 3:00 pm

If you look at the back side of the PI400, you can clearly see that PIN-1 is labeled with text in the plastic case near the GPIO header.

User avatar
Gavinmc42
Posts: 5631
Joined: Wed Aug 28, 2013 3:31 am

Re: Raspberry Pi 400 replacement motherboard

Sat May 15, 2021 10:58 pm

If you look at the back side of the PI400, you can clearly see that PIN-1 is labeled with text in the plastic case near the GPIO header.
Not so clear for old eye without a bight light.

Looks like that connector is plugged in reversed if those two red 5V pins are on the right hand side.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

User avatar
HermannSW
Posts: 4119
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
Contact: Website Twitter YouTube

Re: Raspberry Pi 400 replacement motherboard

Sun May 16, 2021 12:43 am

Gavinmc42 wrote:
Sat May 15, 2021 10:58 pm
Looks like that connector is plugged in reversed if those two red 5V pins are on the right hand side.
Take your Pi400 , keeping front on desk and back high.
Then the GPIO layout is identical to all PIs.
Not sure what you mean with reversed.
Pi400.Pin1.png
Pi400.Pin1.png
Pi400.Pin1.png (179.82 KiB) Viewed 790 times
https://stamm-wilbrandt.de/2wheel_balancing_robot
https://stamm-wilbrandt.de/en#raspcatbot
https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://github.com/Hermann-SW/raspiraw
https://stamm-wilbrandt.de/en/Raspberry_camera.html

User avatar
Gavinmc42
Posts: 5631
Joined: Wed Aug 28, 2013 3:31 am

Re: Raspberry Pi 400 replacement motherboard

Sun May 16, 2021 1:09 am

Not sure what you mean with reversed.
The colour codes on the PCB.
Two red 5V and one orange 3.3V pins are on the right side of the board looking from the front of the Pi 400.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

User avatar
rpdom
Posts: 18692
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: Raspberry Pi 400 replacement motherboard

Sun May 16, 2021 5:16 am

Gavinmc42 wrote:
Sun May 16, 2021 1:09 am
Not sure what you mean with reversed.
The colour codes on the PCB.
Two red 5V and one orange 3.3V pins are on the right side of the board looking from the front of the Pi 400.
The board doesn't appear to be a simple extender. It looks like it turns the connections around so that if you plug a HAT in to it it will be with the connector side toward the Pi 400 and the rest of the HAT away from it.
Unreadable squiggle

User avatar
Gavinmc42
Posts: 5631
Joined: Wed Aug 28, 2013 3:31 am

Re: Raspberry Pi 400 replacement motherboard

Sun May 16, 2021 5:28 am

The board doesn't appear to be a simple extender. It looks like it turns the connections around so that if you plug a HAT in to it it will be with the connector side toward the Pi 400 and the rest of the HAT away from it.
Yep, those tracks don't go straight across.
No idea how 5V show up on those pins.
If that does switch around then the Red probe would be on GND pin 39 and black probe on pin 8 - GPIO 18/TX.
The multimeter would then display -5V?

Where does that PCB come from?
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

Return to “Raspberry Pi 400”