Introduction

This is a tentative to reverse engineer/develop alternative firmwares for the Paintaudio Midi Captain.

This is based on reverse engineering, and is make available to the public hoping it will be useful, but I offer

no warranty whatsoever on anything (if you break it YOU ARE ON YOUR OWN!!!!).

This infomation is similar to other Paintaudio products:

• Midi Captain STD Version Black (Same with no wireless module)
• Midi Captain Mini 6
• Midi Captain Nano 4
• Midi Captain Duo
• Midi Captain One

that seems to be based on the same microcontroller (RP2040) and CircuitPython. But not having them I cannot verify the information.

General Description

The board is based on a Raspberry Pi Core Microcontroller (RP2040 Datasheet) and is programmed using CircuitPython.

The CircuitPython Version on the board as per firmware 4.0 is 7.3.1 (see boot_out.txt)

Links:

• RP2040 Datasheet
• CircuitPython
• Paintaudio Recover uf2 file
• CircuitPython 7.x Library Bundle
• Paintaudio Midi Captain 3in1 Firmware 4.0

Going into update mode

As described in the main product page here, to modify the CircuitPython code you have to enter the Update Mode

On the MIDI Captain this is done pressing switch0 (top left switch) when powering up while being connected via usb to a computer. This will show you the MIDICAPTAIN drive where you can load new firmware and modify the code.

Going into circuitpython bootloader mode

On the board there's a 2 pin header that if you short it and reboot you'll go into circuitpython recovery mode.

Don't mess with it if you don't know what you are doing.

• Paintaudio Recover uf2 file

Circuitpython Serial Debugging Console

1. Install the [mu editor][https://learn.adafruit.com/welcome-to-circuitpython/installing-mu-editor]
2. Start the midi captain in fw update mode (switch 0 pressed at boot)
3. with the mu editor, open the boot.py file and the serial consol
4. comment the following lines to enable autoreload

   # import supervisor
   # supervisor.disable_autoreload()

5. Restart in fw update mode. You will see:

   Adafruit CircuitPython 7.3.1 on 2022-06-22; Raspberry Pi Pico with rp2040
   >>>

6. if you modify the boot.py or the code.py files you will see

   Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.
   code.py output:

7. You can stop the boot pressing Enter at the prompt, or soft reboot with Ctrl+D

Relevant Files and Folder Description

based on the normal+geek_super 3in1 FW4.0

.
├── boot.py                                # Raspbe
├── boot_out.txt
├── code.py                                # Main Python Code
├── lib
│   ├── adafruit_bitmap_font               # Display Libraries
│   ├── adafruit_display_notification
│   ├── adafruit_display_shapes
│   ├── adafruit_display_text
│   ├── adafruit_displayio_layout
│   ├── adafruit_imageload
│   ├── adafruit_progressbar
│   ├── adafruit_st7789.mpy
│   ├── adafruit_framebuf.mpy

│   ├── adafruit_midi                     # Midi Library
│   ├── adafruit_bus_device               #
│   ├── adafruit_hid                      # USB Keyboard
│   ├── adafruit_io                       #
│   ├── adafruit_minimqtt                 # MQTT library?
│   ├── asyncio/                          #
│   ├── adafruit_ticks.mpy                #
│   ├── neopixel.mpy
│   ├── midicaptain.mpy                   # MIDI Captain 
│   ├── midicaptain10s.mpy                # MIDI Captain 
│   ├── midicaptain_ledon.mpy             # MIDI Captain 
│   ├── midigeek.mpy                      # MIDI Captain Geek Mode
│   └── midigeek_C.mpy                    # MIDI Captain 

boot_out.txt

Adafruit CircuitPython 7.3.1 on 2022-06-22; Raspberry Pi Pico with rp2040
Board ID:raspberry_pi_pico

boot.py

import storage
import board
import digitalio
import time

# remove this two lines to auto reload the code when is modified
import supervisor
supervisor.disable_autoreload()

switch = digitalio.DigitalInOut(board.GP1)
switch.direction = digitalio.Direction.INPUT
switch.pull = digitalio.Pull.UP
time.sleep(0.05)

if switch.value is True:
    storage.disable_usb_drive()
    storage.remount("/", readonly=False)
else:
    storage.remount("/", readonly=False)
    m = storage.getmount("/")
    m.label = "MIDICAPTAIN"
    storage.enable_usb_drive()
    storage.remount("/", readonly=True)

code.py

A lot of code to select the firmware mode.

Peripherals

Midi Captain Blue

The board is based on a Raspberry Pi Core Microcontroller (Datasheet), with the following peripherals:

• 10 footswitches
• 30 RGB led, separately addressables
• Midi In/Out
• 2 expression pedal Input
• Battery
• wireless module

GPIO Assignment

GPIO	PERIPERAL	board lib pin / notes?
GP0	encoder switch
GP1	switch1
GP2	encoder A
GP3	encoder B
GP4
GP5
GP6
GP7	neopixel GPIO
GP8	tft_pwm
GP9	switchA
GP10	switchB
GP11	switchC
GP12	tft_dc	(debug_port??)
GP13	tft_cs	(debug_port??)
GP14	tft_spi_clk
GP15	tft_spi_mosi
GP16	uart_midi_tx
GP17	uart_midi_rx
GP18	switchD
GP19	switchDown
GP20	switchUp
GP21
GP22
GP23	switch4	SMPS_MODE
GP24	switch3	VBUS_SENSE
GP25	switch2	LED
GP26		GP26_A0
GP27	ExpPdl1	GP27_A1
GP28	ExpPdl2	GP28_A2
GP29		VOLTAGE_MONITOR

Reverse engineering code

Midi UART

Uart Pins

UART pins can be assigned to any GPIO.

Gpio Loopback Test

1. set a midi cable between midi in and out
2. run the following

Neopixel Led

30 RGB led on the board.

Test Code

scripts/led.py

Display

Adafruit 1.54" 240x240 Wide Angle TFT LCD Display with MicroSD | ST7789 with EYESPI Connector

• https://www.adafruit.com/product/3787

  1.54" 240x240 Color IPS TFT Display

• https://www.adafruit.com/product/4421

Pin Assignments

tft_pwm = board.GP8
tft_dc = board.GP12
tft_cs = board.GP13
spi_clk = board.GP14
spi_mosi = board.GP15

spi = busio.SPI(spi_clk, spi_mosi)

display_bus = displayio.FourWire(spi, command=tft_dc, chip_select=tft_cs)
display = ST7789(
    display_bus, width=240, height=240,
    rowstart=80,
    # colstart=53,
    rotation=180,
)

Wireless Module

The wireless module is a "wireless mouse" serial RF IC

BK2461 Datasheet