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 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 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.
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.)