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rclasen / bluetosis

Bluetooth 4.2 firmware for the Mitosis keyboard

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Bluetosis

Bluetooth firmware for the Mitosis keyboard

Precompiled Firmware

Download the latest .hex file from the releases section. You need to flash the right half only (the left one uses stock Mitosis firmware). Firmware does NOT come with the softdevice because it would violate Nordic redistribution terms. Download softdevice s130 2.0.1 from the Nordic site and flash it the same way as firmware (you need to do it just once). All fimware updates and softdevice go for the right half, left half should be held intact.

Default Layout (Mitosis-BT)

  • Press Adjust + ← ↓ ↑ → to switch between three Bluetooth devices and a receiver
  • Press Fn + Adjust + ← ↓ ↑ → to reset three corresponding Bluetooth devices or erase all bonds

Current firmware version switches into a System Off mode after a few minutes of inactivity to save the battery, and wakes up on hardware interrupt (any key, usually you press something on a home row).

Software

Uploading

ST-Link V2

To flash nRF modules, connect ST-LINK/V2 to the module programming pins (SWCLK, SWDIO, GND, 3.3V - top to bottom) and run this batch (windows 10):

@echo off
set path=C:\SDK\openocd-0.10.0-dev-00247-g73b676c\bin-x64;%path%
set file=%~dp0custom\iar\_build\nrf51822_xxac.hex
openocd -f interface/stlink-v2.cfg -f target/nrf51.cfg ^
-c init -c "reset halt" -c "flash write_image erase %file:\=/%" -c reset -c exit

BluePill

This is basically an $1.80 STM32 board (STM32F103C8T6) that you can use as an ST-Link V2 replacement. No OpenOCD needed. You need to flash the programmer firmware (Blackmagic) first.

  • download Demonstrator GUI from ST-LINK
  • set jumpers to 0-1 0-0, hook up UART (RX - A9, TX - A10)
  • open the latest blackmagic.bin built with make clean && make PROBE_HOST=stlink
  • force select 128K device, select offset 0x08002000, hit Flash
  • set jumpers to 0-0 0-0, hook up your favorite SWD board (SWCLK - A5, SWDIO - B14)
  • get the latest zadig, update all drivers to libusbK or something
  • run something like arm-none-eabi-gdb --quiet --batch -ex "target extended-remote \\.\COM5" -ex "mon swdp_scan" -ex "att 1" –ex "load nrf51822_xxac.hex" –ex kill

You can also merge softdevice using mergehex utility from the nRF5x Command Line Tools but it's faster to just flash it once.

mergehex.exe -m s130_nrf51_2.0.1_softdevice.hex nrf51822_xxac.hex -o out.hex

Building

Copy this repository to the nRF5_SDK_12/bluetosis folder.

Mind that symlink or junction won't work on Windows 10 for some reason (GCC Makefile error ... is a directory. stop).

IAR

Open .eww, hit Make, that's it. I'm using a single plate (reversed) version for the debug configuration (modules soldered to the top of the PCB), to build standard version remove COMPILE_REVERSED from defines.

GCC

sudo apt install openocd gcc-arm-none-eabi
(edit nRF5_SDK_12/components/toolchain/gcc/Makefile.posix, set GNU_INSTALL_ROOT := /usr/)
cd nRF5_SDK_12
git clone https://github.com/joric/bluetosis && cd bluetosis
cd firmware/custom/armgcc && make

Working GCC linker settings for softdevice s130 2.0.1 and YJ-14015 modules (256K ROM, 16K RAM) appear to be:

  FLASH (rx) : ORIGIN = 0x1b000, LENGTH = 0x25000
  RAM (rwx) :  ORIGIN = 0x20002000, LENGTH = 0x2000

To build with this settings, set stack and heap to 1024 or something in gcc_startup_nrf51.S (originally 2048). You could also use Makefile defines:

ASMFLAGS += -D__HEAP_SIZE=1024 -D__STACK_SIZE=1024

Debugging

There is a built in NRF_LOG in Nordic SDK but it doesn't work with GCC (probably no memory). I had to write a small drop-in replacement. In IAR you can try using NRF_LOG_ENABLED and NRF_LOG_USES_UART in sdk-config.h. Note that built in debugging has its own pin settings in sdk-config.h (not the ones that are in the custom_board.h).

Neither nRF51822 nor ST-Link V2 have SWO pin for printf (there is no tracing hardware in the nRF51 series), so I had to use UART. You only need ONE pin to print messages via UART (e.g. using Arduino IDE Serial Monitor). There are no free broken out pins on the Mitosis so I've used pin 19 (bottom right key) as TX_PIN_NUMBER and it worked.

Hook up a single UART RX pin at 115200 baud (currently pin 21, key S15 or S23). You will also need common GND and VCC to make it work. It doesn't really interfere much with the keyboard matrix so you can use any pin you want, just don't use the same pin for TX and RX to avoid feedback.

You can also use Blackmagic probe for debugging. It is actually the best because it has a built in UART (pin A3) on the second virtual COM port so you won't need another USB. I personally use Bluepill board with Blackmagic firmware as a programmer and a debugger and Putty with enabled local echo as a serial monitor.

Status

Works

  • Bluetooth and Gazell timesharing
  • Battery level reporting via Bluetooth
  • Debugging via UART
  • Basic QMK layout support
  • Bluetooth pairing shortcut
  • Switching between RF and Bluetooth modes
  • Switching between Bluetooth devices

TODO

  • Full QMK/TMK suport (maybe)

QMK support is still in progress (firmware compiles fine without QMK)

QMK firwmare has massive incompatibility issues with ICCARM (IAR) that can't be fixed with preprocessor. So it's either a fully-GCC setup (armgcc and maybe uVision Keil) or patching QMK (changes are small but I don't know if they ever get merged to the upstream). I've patched and compiled QMK for ICCARM but couldn't get correct keycodes so far.

QMK incompatibility issues

  • Excessive and unnecessary binary literals (e.g. 0b011 is C++14 only), should use hex or decimals
  • GCC-specific switch case ranges (case A ... Z, ), should use if and else
  • GCC-specific __attribute__ keyword, e.g. __attribute__ ((weak)), should use __WEAK define
  • Inplace initializations (#define MACRO(...) ({static const macro_t __m[]; PROGMEM={__VA_ARGS__}; &__m[0]}))

Patching QMK for IAR

  • add #ifdef __ICCARM__ for IAR-specific code
  • add __attribute__(x)= to the preprocessor directives, use __weak or whatever instead
  • add dummy Atmel-specific variables and functions PORTF, PORTD, etc.

QMK embedding guide

  • add QMK_KEYBOARD_H="your_hardware_name.h" to the preprocessor directives
  • add #include "keyboard.h", add QMK paths (quantum/, tmk_core/common/, etc.)
  • implement timer_read32() if it's incompatible (e.g. use app_timer_cnt_get for nrf5x)
  • implement matrix_row_t matrix_get_row(uint8_t row) callback (just read from array)
  • implement host driver callbacks, add host_set_driver(&driver) to the init sequence
  • add keyboard_task() to the main loop

See this GCC-only TMK core-based project for example (all API calls are precisely the same):

Summary

Mitosis was NOT a Bluetooth keyboard (until now). It used a proprietary rf-protocol (Gazell) and a dedicated receiver. Global layers need two wireless channels: Bluetooth HID and something for the communication between halves. Possible solutions are listed below.

Gazell

There are examples of Bluetooth and Gazell running concurrently (this is what current firmware uses):

Bluetooth UART service

There are a few split keyboards that successfully run Bluetooth HID and Bluetooth UART service concurrently. Most of them use Adafruit nRF52 library and simple sketches written and compiled in Arduino IDE.

Arduino nRF5

There is Arduino-nRF5 by Sandeep Mistry that supports nRF51. You could use arduino-BLEPeripheral library for sketches. Works fine with BLE400 board (Arduino IDE setup, wiring). Sadly this library has multiple issues with Windows 10.

Arduino nRF52

Note that Arduino nRF52 builds (usually based on Bluefruit nRF52 boards) are NOT compatible with the Mitosis keyboard (softdevice s132 and all the software is nRF52-only, Mitosis is nRF51-based).

BlueMicro

This is a drop-in Pro Micro replacement that is compatible with Arduino nRF52 boards (it's NOT compatible with nRF51). BlueMicro is open source, official repositories are BlueMicro_BLE (firmware) and NRF52-Board (hardware).

Hardware

Original Mitosis hardware repository: https://github.com/reversebias/mitosis-hardware

  • ST-LINK/V2: $2.54, had in stock (you can also use $1.80 STM32 board instead).
  • YJ-14015: nrf51822 modules, 3 pcs: $10.5 ($3.50 * 3), free shipping, need 2/3, so $7.
  • 10 main PCB's from EasyEDA, $13.32 ($2 + $11.32 for trackable shipping), used 4/10, so $5.32.
  • 3 receiver PCB's from OshPark, $5.40, free shipping, used only 1/3, so $1.80.
  • Arduino Pro Micro from Aliexpress (price varies from $2.54 to $4), had in stock.
  • Si2302 mosfets: board survives reverse polarity for a while, you may just short the pads.
  • ASMB-MTB1-0A3A2 from Aliexpress (or Cree CLVBA-FKA, or 3 single LEDs, very optional)
  • AMS1117: 5v to 3v regulator, had in stock. You probably can use diodes for 2v drop.
  • 1206 4.7k resistor arrays, 2 pcs: had in stock (taken from an old motherboard).
  • Switches and caps: most of you have more than you can handle.

Total

  • Keyboard: $12.32 ($7 + $5.32) and I got enough PCBs to build 3 and they can reuse receiver.
  • Receiver: $7.84 ($3.50 + $1.80 + $2.54) firmware upgrade to ble and you wouldn't need it at all.

So, about $20 for a single keyboard.

PCB Manufacturers

Schematics

There were speculations that Core 51822 has 32 GPIO pins available, so it's possible to make an Atreus62 without using a keyboard matrix. It is not true. GPIO 26/27 are shared by the 32kHz crystal and there are only 31 GPIOs hence PIN31 is not existing. So you could only have 29 keys on each side (58 total) if you manage to layout them without crossing.

Mitosis Clones

References

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Bluetooth 4.2 firmware for the Mitosis keyboard

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