STM32 Keyboard

Originated from HKUST Elec3300 project

Feature List

• 6*14 key matrix
• Programmable 6*14 RGB matrix
• On-board OLED display(SSD1306)
• Volume control by Rotary encoder
• Fingerprint sensor
• Programmable Macro
• Sleep Mode(low power mode)
• Connection:
  • Bluetooth
  • USB
• Power:
  • USB power supply
  • Battery(with USB charging)

Feature Specification

RTOS

We use RTOS to manage all the tasks

1. RGB Thread:
   1. Change pwm pulse width to control color
2. Key Thread:
   1. Detect key pressed and send HID report to computer
   2. Read volume encoder
3. Others Thread:
   1. System Debug LED Blink
   2. Read Battery ADC
4. Key Interrupt
   1. Generate an interrupt whenever a key is pressed to keep the system awake.
5. Fingerprint Sensor Interrupt
   1. Since Comparing Fingerprint is quite a time-consuming process, it will delay the system so bad if using polling. Hence, we use a pin to detect interrupt whenever there is finger being detected by fingerprint sensor.

Key Input

Via Bluetooth:

• Use a bluetooth HID connection (RN42) to communicate with the computer to type characters
• Utilize the button matrix system as a way to indicate which character are being input to the computer

Via Cable:

• Use STM32 USB HID interface to communicate with the computer
• Use the same Button matrix system to indicate which character is being inputted

Volume Control

• Use an encoder(timer) for detecting the volume changes and sent it to computer by HID.

RGB Backlight

• To control the Brightness and Colour, WS2812B uses uptime and downtime indicate ‘0’ and ‘1’ data.
• Since changing PWM pulse width by delaying is not fast enough to handle the data transition (Sending ‘0’ byte then ‘1’), we refer to DMA to solve this issue as it is more performant.
• Different RGB pattern:
  • Static
  • Breath
  • Loop
  • Disable

Sleep Mode

• Power-consuming parts will be disable when keyboard is idle for certain amount of time.
• Wake up by keys interrupt.

OLED

• It uses I2C protocol in order to communicate with the OLED screen
• OLED serves as an User Interface for status and setup
• Pages:
  • Status(Connection mode, Battery)
  • RGB Mode(Static, Breath, Loop, Disable)
  • RGB static
  • Marco
  • FingerPrint

Battery

• The battery is being read by an ADC, which uses a continuous mode.
• The value is read, and converted into percentage in our OLED

Fingerprint Sensor

• It uses UART as a communication system to register, scan, and detect the fingerprint.
• Furthermore, having an interrupt when a finger is being detected help to reduce the need for pooling if a finger is placed on the scanner

Environment

Download all of these before continuing:

• arm-none-eabi-gcc for compiling (make sure you use the lastest version)
• OpenOCD for flashing and debugging
• CMake for the build system
• Ninja or some kind of Make
  • Ninja is faster and easier to install on windows
  • Mac/Linux can just use inbuilt Make easily

Package Manager: Use Brew on Mac

https://brew.sh/

brew install --cask gcc-arm-embedded
brew install ninja
brew install cmake
brew install open-ocd

Package Manager: Use Anaconda

https://anaconda.org/ While Anaconda is usually for handling Python packages you can find many. You may need this anyway

conda install -c conda-forge cmake ninja 
conda install -c litex-hub openocd # max/linux
conda install -c m-labs openocd # windows/linux
conda install -c dhgoldberg gcc-arm-none-eabi

Package Manager: Use Chocolatey on Windows

https://chocolatey.org/

choco install gcc-arm-embedded
choco install openocd
choco install ninja
choco install cmake

Building and Flashing:

In the command palette

• type build and find CMake: Build, remember the keyboard shortcut shown on the right for future use
• use CMake: Build Target and choose flash
• use CMake: Set Build Target to choose the default build target
  • this would make CMake: Build run that target
  • the default default build target is all which just compiles

PCB

TODO

Video Demo on Youtube

https://www.youtube.com/watch?v=Xp9VSN2TY44