Worklog Pi-Xel

[thedrew]

A few months back, I was thinking of my childhood and impulsively purchased a Retroid Pocket 2 for nostalgia after seeing all of the good reviews. To be honest, I was disappointed and has been in a drawer ever since.

It's a bit of a learning process for me as I don't know much about the pi and I'm still learning as I'm going, but the goal is to build something better and more capable than the Retroid.

Here is a quick list of features I'd like to have:

- 3 to 4 hours battery life
- 800x480 4.3" IPS display (Now changed to a 5" IPS)
- 24bit direct drive from pi GPIO
- LCD brightness control
- Front firing speakers
- Removable micro sd card
- Usb slot for transferring roms to micro sd
- Arduino micro as gamepad with switch sticks
- Modded RVL-PMS as bms

I'll be using Vita action buttons and Dpad.

Current state of top half:

Current state of bottom half:

This is the custom direct drive circuit. This is a preview of a board but will be a flex. It is designed to be soldered on the bottom side of the pi, as when the pi board is screwed down in the case, the bottom side of the pi will be facing up toward the LCD. I'm using a PT4103 as the backlight driver and will have dimming control via a potentiometer thumbwheel.

I will be extending the micro sd slot from the pi to a simple custom board. An FFC connector will be soldered in alignment of the micro sd slot on the pi and connected to the board via an FFC cable.

There will be about 6 or so custom boards total for this handheld to make the assembly/internals much easier and cleaner. For the modified RVL-PMS, essentially I will be using the 5v reg but cutting off the top half of the board as I will not be using any of those regs and cannot fit the PMS in the case without trimming it. I'd rather not redesign the whole RVL as I already have extra blank boards laying around from a previous JLC order.

For the audio board, I will be using the HXJ8002 ic as it is class AB with super low distortion and practically doesn't distort at full volume. I've used this chip before and is my favorite audio amp to work with so far.

I still have the button boards, audio board, and peripheral board to finish and I'll be done with all of the custom boards .

Lastly, I found a different 800x480 4.3" IPS LCD that is higher quality than the older 4.3" IPS screen we've all been using on the forums. Looks fantastic with a direct drive board I've been testing it with. It has better saturation, better contrast, and better viewing angles. Tried to capture it on camera but is way more apparent in person.

Left old, right new

Here's the link if anyone is interested. I did test this new LCD with an RTD2660 driver board and it doesn't work. Maybe a firmware or timing thing as the LCD has the same pinout.

https://www.aliexpress.com/item/1608099318.html?spm=a2g0s.9042311.0.0.adf14c4dFfW8ZZ

 

[thedrew]

This has been a slow project as I'm challenging myself with custom pcbs. It will make it much easier and cleaner to assemble.

I received a couple custom boards and a flex board.

Here are the simple controller boards. The switch stick ffc connectors are off on purpose due to limited space I'm working with as well as the stick placement, but should still work fine .

The flex board is for the LCD to be directly driven from the pi, pure digital with a backlight circuit to the left. I'll have a thumbwheel pot to control brightness.

This was my first flex I've designed, and didn't realize the more ground you have the less flexible it is... Whoops. It doesn't really need to be flexible anyway haha.

Last, I really didn't want to redesign the whole RVL-PMS board, so the easiest and quickest solution was to modify the board by cutting off the upper portion to be able to fit it in the case.

Next steps are to finish designing the audio board, peripheral board, and shoulder button boards.

 

[Stitches]

This has been a slow project as I'm challenging myself with custom pcbs. It will make it much easier and cleaner to assemble.

I received a couple custom boards and a flex board.

Here are the simple controller boards. The switch stick ffc connectors are off on purpose due to limited space I'm working with as well as the stick placement, but should still work fine .
View attachment 16152
View attachment 16153
View attachment 16154

The flex board is for the LCD to be directly driven from the pi, pure digital with a backlight circuit to the left. I'll have a thumbwheel pot to control brightness.
View attachment 16155
This was my first flex I've designed, and didn't realize the more ground you have the less flexible it is... Whoops. It doesn't really need to be flexible anyway haha.

Last, I really didn't want to redesign the whole RVL-PMS board, so the easiest and quickest solution was to modify the board by cutting off the upper portion to be able to fit it in the case.
View attachment 16156

Next steps are to finish designing the audio board, peripheral board, and shoulder button boards.

Just a lil off the top

 

[thedrew]

Well, made a design change from a 4.3" screen to now a 5". The deciding factor was battery life. With the 4.3" design, I was able to fit 4800mah batteries but only lasts 2 hours. With the 5" design, I can fit 8000mah batteries, which should last closer to 4 hours. So far, everything was designed for the smaller screen so now with the larger screen design should give me a little extra room for everything. Luckily, my direct drive flex still fits alignment wise with the new screen.

Did a quick test print of the top and everything fits like a glove. Terrible lighting for the next few photos...

The switch stick cables line up just right to where the ffc connectors will be on the controller boards.

I designed a sound chamber for the speakers. Have yet to test but should have more depth than the usual speakers in a portable.

Not the final color scheme, just for testing

 

[thedrew]

Assembled my flex and what a pain where the sun don't shine... Had to redo the lcd ffc connector about 5 times since this flex kept bending when I added heat. Probably would have been better off using an actual pcb. Oh well, experience was gained designing and assembling my first flex. All I have to do is solder the backlight ic once it comes in and fingers crossed it will work first try!

Had to use the microscope to see if all of the pins were finally making contact. Not perfect but should be fine.

Also assembled my sd card extender board.

Need to order a longer ffc cable but not sure if I need to wire anything additional for the sd card to work since the pi board has traces for sd detect and my board doesn't have that. So maybe just the detect trace needs to be wired to ground so it's always detected. I'll find out soon enough...

EDIT

The good news is that the trimmed PMS, micro sd relocation, and backlight circuit are confirmed working which I'm happy about, but...

The display flex on the other hand is kind of working. The colors and image are a bit wonky

The text sort of looks garbled.

So, I'm wondering if the direct drive guide I used to create my display flex is incorrect or I made a dumb mistake haha. Could also be the config as I borrowed code from the board I was using for testing that maybe doesn't work with my display flex.

But in that case wouldn't I get no display at all if the pinout was wrong?

This is the guide I used if anyone's wondering:
24bit Direct Drive Display with Pi GPIO

I think I just have to mess with the software. To be honest, having no experience with a pi prior and to gett to this point I'm pretty happy with though haha.

 

[Shank]

Last, I really didn't want to redesign the whole RVL-PMS board, so the easiest and quickest solution was to modify the board by cutting off the upper portion to be able to fit it in the case.
View attachment 16156

 

[thedrew]

After many hours, the solution ended up being so simple. In the config file, the dpi display was set to the wrong color profile. Everything is working perfectly now as well as brightness control with a potentiometer wheel.

 

[thedrew]

Project is coming along nicely. Assembled another board and so far most everything is working.

This board is for charging, usb, audio, and brightness control. The audio amp ic is on the bottom of the board as well as a tiny RGB LED for the PMS. The ic behind the type c charging port negotiates 9V from a smartphone fast charger. Maybe not the best solution but actually works pretty well.

Everything works other than troubleshooting audio and the pi runs all the games at super fast speeds that are unplayable for some reason... Will need to look further into that.

All that's left to do is just to figure out the shoulder buttons and doing some final tweaks to the case. Yet still seems like there's so much more to do...

 

[vipe_202]

Love the design of your pi build, one question I had was your PMS mod. The 5v buck boost is that the one that is by default list on the BOM for the RVL PMS? I had assumed it would work but wanted to double check

 

[thedrew]

Love the design of your pi build, one question I had was your PMS mod. The 5v buck boost is that the one that is by default list on the BOM for the RVL PMS? I had assumed it would work but wanted to double check

Thank you, and yes it is!