mai_pico/README.md

# Mai Pico - Maimai Style Mini Controller

<img src="doc/main.jpg" width="80%">  
<img src="doc/assembled.jpg" width="80%">

Features:
* Made with a 15.6 inch portable screen.
* Arcade-like experience.
* Dual-player is possible.
* All source files open.

Thanks to many respectful guys/companies who made their tools or materials free or open source (KiCad, OnShape, InkScape, Raspberry things).

## Notes
This project is the most complex one.
* It needs a custom etched ITO glass and a portable display.
* Heavily depends on 3D printing.
* Requires skills to solder tiny components.
* Requires many other DIY hands-on skills.
* The IO PCB is still in prototype state, it works, but the layout and connectors are not perfect. You may need to solder directly from Pi Pico's pins. I'm just too lazy to release a new version.
* I didn't design the housing, so it's your job to make it look nice and structually stable, follow your imagination and taste.

## Check Out My Other Projects
You can also check out my other cool projects.

<img src="https://github.com/whowechina/popn_pico/raw/main/doc/main.jpg" height="100px">
<img src="https://github.com/whowechina/iidx_pico/raw/main/doc/main.jpg" height="100px">
<img src="https://github.com/whowechina/iidx_teeny/raw/main/doc/main.jpg" height="100px">
<img src="https://github.com/whowechina/chu_pico/raw/main/doc/main.jpg" height="100px">
<img src="https://github.com/whowechina/mai_pico/raw/main/doc/main.jpg" height="100px">
<img src="https://github.com/whowechina/diva_pico/raw/main/doc/main.jpg" height="100px">
<img src="https://github.com/whowechina/aic_pico/raw/main/doc/main.jpg" height="100px">

* Popn Pico: https://github.com/whowechina/popn_pico
* IIDX Pico: https://github.com/whowechina/iidx_pico
* IIDX Teeny: https://github.com/whowechina/iidx_teeny
* Chu Pico: https://github.com/whowechina/chu_pico
* Mai Pico: https://github.com/whowechina/mai_pico
* Diva Pico: https://github.com/whowechina/diva_pico
* AIC Pico: https://github.com/whowechina/aic_pico

## **Disclaimer** ##
I made this project in my personal time with no financial benefit or sponsorship. I will continue to improve the project. I have done my best to ensure that everything is accurate and functional, there's always a chance that mistakes may occur. I cannot be held responsible for any loss of your time or money that may result from using this open source project. Thank you for your understanding.

## About the License
It's CC-NC. So DIY for yourself and for your friend, don't make money from it.

## HOW TO BUILD
### PCB
* Go JLCPCB and make order with the gerber zip file (latest `Production\PCB\mai_io_v*.zip` and `Production\PCB\mai_button_v*.zip`), regular FR-4 board, 1.6mm thickness. You need 1x io PCB and 8x button PCBs for one Mai Pico con.  
  <img src="doc/pcbs.jpg" width="50%">
* 1x Rasberry Pico Pi Pico or Pico W.  
  https://www.raspberrypi.com/products/raspberry-pi-pico
  Becareful of 3 pins that are at the other side, they're difficult to solder and may leave air bubbles.  
  <img src="doc/solder_usb_txrx.jpg" width="60%">
* 1x USB Type-C socket (918-418K2023S40001 or KH-TYPE-C-16P)
* 3x MPR121 modules, there're many types in the market, choose ones like this.  
  https://www.sparkfun.com/products/retired/9695  
  Before solder MP121 module to the main PCB board, remember to **cut (unshort) the ADDR pin** which is short by default.  
  <img src="doc/mpr121_cut.png" width="40%">
* Leave U5, U6, U7 area discrete components empty as we're using MPR121 module, not the chip.
* 2x 0603 5.1kohm resistors (R20, R21) for USB.
* 1x SN74LV1T34DBVR (SOT-23-5) level shifter (U8), if you can't find one, use a 0603 10ohm resistor (R4) as an alternative.  
  https://www.lcsc.com/product-detail/Buffer-Driver-Transceiver_Texas-Instruments-SN74LV1T34DBVR_C100024.html
* 4x 0603 1uF (0.1~1uF all fine) capacitors (C1, C2, C3, C7), OPTIONAL, recommended.
* 16x WS2812B-3528 RGB LEDs (each button needs two).
* 8x Kailh Choc v1 key switches, linear, 30gf to 45gf ones.  
  https://www.kailhswitch.com/mechanical-keyboard-switches/low-profile-key-switches/burnt-orange-switch.html

### ITO Glass
* Find a service to make custom etching ITO coated glass. The AutoCAD file is `Production\CAD\mai_pico_ito_v*.dwg`. Use 2mm thickness, 10-20ohm sheet resistance ITO coated glass.
  <img src="doc/ito_glass.jpg" width="70%">
* The ITO coated glass is connected to the IO PCB by "zebra cable" (1.6mm pitch: 0.8mm black part and 0.8mm clear part). A silicon heater head at 200°C is used to stick the zebra cable to the gold finger part of PCB and ITO coated glass. The formal name of this cable is "Heat Seal Connector".  
  <img src="doc/zebra_cable.jpg" width="70%">
* Custom ITO coated glass is relatively expensive, but ours is small, so it's not like arcade-size expensive. This is the shop I ordered the ITO glass. The minimal batch is around 5 pieces. But they provide service only in China as far as I know.  
  https://shop378788148.taobao.com/?spm=2013.1.1000126.2.305e16c4LFf1GW

### Button Ring
* Print out the 8x set of base, link, button and cover from `Production\3DPrint\mai_*.stl`.
* Buy 8x 2mm (diameter) * 40mm (length) steel shafts, they're used as the button hinge.
* Here's how to assemble them, hinge shaft and components on PCB are not shown in this rendered image.  
  <img src="doc/assemble.jpg" width="80%">
* Here's how I assembled the ring. Please note that wiring for the button switches is missing in these pictures.
  * All discrete components ready.  
    <img src="doc/assemble_1.jpg" width="60%">
  * Solder the button PCB first.  
    <img src="doc/assemble_2.jpg" width="60%">
  * PCBs are daisy-chained using short and soft 4-wire cable, they're LED_GND, LED, LED_5V and BUTTON_GND. The BUTTON signal pins are not soldered yet, you can later wire them. Don't worry about the order of button GPIOs, because they can be remapped through command line interface.    
    <img src="doc/assemble_3.jpg" width="60%">
  * You need 3M5423 UHMW film tape (or similar hard and super-smooth PTFE tape with 0.2-0.3 thickness). It is to lubricate the button surface that touches the keyswitch.  
    <img src="doc/button_lub.jpg" width="60%">
  * Assemble the 3D printed parts together with the PCBs.  
    <img src="doc/assemble_4.jpg" width="60%">
  * Use shaft to expand the support holes a little bit, and apply some keyboard switch lubricant such as Krytox 205G0 to make the shaft super smooth.  
    <img src="doc/assemble_5.jpg" width="60%">
  * Each `link` needs 8x M2*4mm screws to connect two `base`s together.  
    <img src="doc/assemble_6.jpg" width="60%">
  * Install the cover, each needs 2x M2*5mm screws.  
    <img src="doc/assemble_7.jpg" width="60%">


### Portable Display
  * Resolution: 1920*1080, size: 15.6inch, refresh rate: 120Hz (recommended) or 60Hz, built-in speakers.
  * They're easy to find. Choose cheap or even tiny-flawed ones, they're much cheaper and work just fine.
  * There're 2 types of driver board, one is micro-HDMI only and the other supports type-C display (for convenient Nintendo Switch connection). They're both OK.  
  https://www.amazon.com/s?k=portable+display+15.6+120hz&s=price-asc-rank&crid=1CCA2EAYLZDBE&qid=1697276847&sprefix=portable+display+15.6+120hz%2Caps%2C387&ref=sr_st_price-asc-rank&ds=v1%3AqoS0mks05q225yuL8reh50fEEBkTZ583nMPEZJwjXAk

### Glue Things Together
  * I use 3M VHB tape (0.5mm or 1mm thickness) to stick the button ring, the ITO glass and the monitor together.
  * Only use a little tape, I use 4 small pieces to stick ITO glass to the display and another 4 small pieces to stick button ring to the ITO glass.
  * Don't apply the tape on the traces of the ITO glass, you can see the traces or pads at certain angle.

### Housing
  * It's your job to design it and make it look nice.

### Firmware
* UF2 file is in `Production\Firmware` folder.
* For the new build, hold the BOOTSEL button while connect the USB to a PC, there will be a disk named "RPI-RP2" showed up. Drag the UF2 firmware binary file into it. That's it.
* Button GPIOs can be remapped using `gpio` command.
* LED and Touch protocols are implemented following Sucareto's research at https://github.com/Sucareto/Mai2Touch.
* It has a command line to do configuration. You can use this Web Serial Terminal to connect to the USB serial port of the Mai Pico. (Note: "?" is for help)  
  https://googlechromelabs.github.io/serial-terminal/  
  <img src="doc/cmd.png" width="80%">
* It implements 3 COM ports, one is for command line and the other two are for LED and Touch. By issuing "whoami" to the command line, each COM port will print their identities.
* Button signal is sent to the host by HID Joystick or HID NKRO (keyboard). There're two set of NKRO keymaps, use `hid <joy|key1|key2>` to switch between them.

## CAD Source File
I'm using OnShape free subscription. It's powerful but it can't archive original designs to local, so I can only share the link here. STL/DXF/DWG files are exported from this online document.  
https://cad.onshape.com/documents/d8b39d27c9cb7990d9ce4d46/w/2c1baa71e391bfd1246f122b/e/f87f0f1c373fe2186ddc5c9c?renderMode=0&uiState=652a665608b4e07137e3861a