[Solved] Left directional button is turning the device on!?

The problem:

The Problem:

The problem was that when the Pokitto was not turned on and its left directional button was being pressed, the device would power up.

This was noticable by the device behaving exactly as if the power switch had been turned on for as long as the left button was held, including:

  • The blue power light being on
  • The screen turning on
  • The bootloader loading

Furthermore, when the device was turned on via the power switch the left directional button would not be detected by any game.

The Cause:

The cause of the problem was that there was a small amount of solder that was connecting pins 99 and 100 of the MCU*.

Pin 99 is the MCU’s wake up signal.
Pin 100 is the pin for the left button.

Hence these two pins being soldered together was causing the wake up signal to fire when the left button was pressed.

This solder was an excess amount of solder that unintentionally introduced during the manufacturing processes as it was building up on the PCB’s** stencil***. This problem is now known and counter measures will be taken.

Note that this issue can affect other pins, particularly those in the bottom left corner and top right corner of the MCU, and as such this issue may manifest itself in other ways.

* MCU - microcontroller unit - an integrated circuit’s equivalent of the CPU of a full sized computer, the ‘electronic brain’ that controls all other components.

** PCB - printed circuit board - an integrated circuit’s equivalent of the motherboard of a full size computer, the circuit board that holds and connects all the individual components.

*** PCB stencil - when PCBs are manufactured they use a stencil (a sort of board with holes cut out of it, much like those used for drawing) to uniformly apply solder to a board (and in some cases, to solder multiple boards at once).

The Solution:

The solution was to somehow remove the soldering paste from the two pins that had been soldered together.

In my case I used a small, thin sewing needle to gently scrape away the solder, being careful to not damage the MCU or the PCB.

If you have access to more sophisticated desoldering facilities I would recommend using those as they are less likely to cause damage.
In my case I already had a replacement board so I was not as concerned about causing damage.

Two popular methods for removing solder are to use a desoldering pump (also known as a solder sucker) or to use a desoldering braid (also called a desoldering wick or a solder wick).

These are well recognised methods and I would advise you use them if you are able to and are concerned about damaging your Pokitto board.


Original Post:

I finally I sat down and put my Pokitto together (forgoing the missing screw) and I noticed something odd.
For some reason my left direction button isn’t working.
On top of which, it appears that when I have the board off, pressing the left direction button actually turns the board on.

I pulled the board away from its housing so the only thing left connected was the screen and it still turns the board on, so it looks like it’s probably a board fault. I can’t spot anything visibly wrong, but I’m a programmer, not an electrician/hardware designer so I have absolutely no clue what’s up with it.

Edit: Here’s a video uploaded to Youtube to demonstrate:

(Coincidentally my hand’s internet debut.)

2 Likes

Wow. Sounds downright spooky!

Edit: I am going to look at the wiring. That is an odd thing to happen

1 Like

Thats most likely a short circuit of some sort. Are you sure the missing screw is not hiding jammed on the PCB somewhere?

EDIT: this is not a joke. Check around the Li-Po battery and the left button on both top and bottom of the board, also around the main CPU.

There is 3.3V in the “leg” of the left button switch that might be shorted to the wake up line. Same fault would be visible also as a non-working left button

Pokitto does not have a hardware switch, it has a wake up, because we will be using the RTC for waking later.

1 Like

There is a chip right below the left switch component (on the front side).

If there is something between this chip and the button component (both marked in white) it could cause exactly the symptoms you describe.

1 Like

I have made a video but this site doesn’t accept any video formats so I may have to host on youtube if you’d like a look.

The video is somewhat grainy because my camera is old and I had to condense the video to a smaller format.

Here’s a picture of the board from the left side:

And here is the back:

As far as I can tell, everything appears normal.
I will try to get my hands on a better camera tomorrow.

Is there a technique to removing the battery?
Is it taped down or does it slide out?

I’m trying to be cautious because some parts (like the clips and the battery) are quite stiff and I’m worried about breaking anything (I’m sure the screen connector wouldn’t appreciate being torn).

1 Like

Well, I guess there’s some spooky events just in time for Friday the 13th :stuck_out_tongue: #2spooky4me

I hope you can fix that and don’t have to order a new Pokitto, because that’s obviously unpleasant (and I can’t wait to see more content on the Pokitto! We need a floating skulls game! :stuck_out_tongue:)

1 Like

I completely forgot it was Friday the 13th.
First time one of those has ever brought me bad luck.

Usually they’re (ironically) actually incredibly good days because the superstitious people are extra careful so less accidents happen.

If I have to get a replacement shipped or send this one back for inspection I’d probably be willing to since I’m a fairly patient person, but it would be a tad awkward since the address it was shipped to isn’t my address.

(I promise that as soon as the issue is fixed my first demo will involve some skulls.)

2 Likes

If you use the youtube link in a post it gets converted to the video. You do not need to lower the video quality for youtube.

Can you post sharper images of the pcb from top? Maybe we can help diagnosing

@Pharap PM me your name & address. I think your order was combined with someone elses?

[off-topic] Finally, I can see the other side of the moon Pokitto PCB. One of my doodles made it to the PCB :slight_smile:

This is the best I can offer at the moment:



The problem is that the raw video is 15MB which would take quite a while to upload to youtube, and even then it’s only for the purpose of showing that the left button does indeed cause the power to turn on, so waiting 30 minutes or longer to upload a large video file to Youtube just to show that the power turns on when I press the left button seems like a bit of a waste of time.


Was there a doodle contest or something?
I’d have happily donated some doodles.
I’m not a very good artist but I try.

Do you need my full name or will initials do?

(Sorry for taking so long to reply, I’ve been busy today.)

Well, I just need some address to send a new pcb.

1 Like

There will be new iterations of the board and more chances for doodles. I came up with the idea and didn’t have a lot of time to wait (24 hrs actually) on this round. I would have put more but vectorizing and fitting the doodles on the graphics took time.

1 Like

Just fyi @Pharap : i did not get the replacement sent yesterday, was too busy. but it left today and is on its way

extra set of screws and bonus backcover included. all keys tested

1 Like

Thank you. I appreciate that you have many other jobs that need doing so a small delay is no concern.

When my replacement board arrives I will most likely ask about the procedure for sending my old board back so I can make sure I do it correctly.
(Perhaps it would even make a good wiki article, undoubtedly someone else will have to do the same at some point in the future.)

After the board arrives you can check the board over whenever it is convinient to do so. As nice as it would be to know the cause, there’s no rush to find out what the problem is as I suspect you will have more urgent problems to solve.

Totally agree. We shall do so.

Btw, you are getting a backcover color nobody else has! (proto series)

1 Like

Ooh, I get to be a guineapig.
(Hopefully it’ll be a colour I like.)

Spoiler: it is brown.

:joy:

2 Likes

No actually that color was in the machine when we began testing the molds. I needed to put the PCB in the back cover to protect it when shipping - so I took the first back cover at hand.

So it is a color that will never see production :grin:

1 Like