CaseCommander

Computer case environmental controller with USB control interface

Planned features

• Fan speed control
  • Classic 3pin fans via variable supply voltage
  • PWM 4pin fans via direct PWM signaling
  • Various modes (static, threshold, curve, target [PID], TBD)
• Temperature sensor readout and feedback
• RGB LED strip control
  • SK9822 support
  • Various modes (TBD)
• All functions should be inspectable and controllable from some form of PC (GUI) software

State of the art (as of 2020/06/16)

• Design of supporting circuitry for variable voltage and PWM control is complete, yet to be tested and validated
• Implemented firmware features:
  • USB communication
  • fan tachometer reading
  • SK9822 initial test implementation using SPI peripheral

Hardware

The chosen MCU is an ARM Cortex-M3 STM32F103C8, which is readily available from chinese resellers on a prebuilt board known as Blue/Black Pill.

There is also some supporting circuitry, consisting of a N-channel MOSFET (IRF3205 or IRF520N or equivalent) and gate driver (TC4420 or equivalent), one combo to drive each variable voltage control channel.

Development environment

Cross-platform? (Linux on Windows)

First try, Windows Subsystem for Linux: worked well up to the point of actually trying to flash the MCU -> WSL does not expose USB devices.

Second try, MSYS2: same issue as WSL.

My current environment is a Ubuntu 20.04 Server virtual machine which I SSH into from Visual Studio Code using its "Remote - SSH" extension (works really well). As a debugger probe I am using a SEGGER J-Link.

• Ubuntu 20.04 with these packages: build-essential python-is-python3 libncurses5 (also openocd if you don't want to use proprietary software, but read on...)

• Visual Studio Code with these extensions: C/C++, Cortex-Debug, Cortex-Debug: Device Support Pack - STM32F1

• gnu-arm-embedded toolchain

• J-Link Software for Linux 64-bit

  gnu-arm-embedded and J-Link software binaries paths must be set in the PATH (eg. by setting them in ~/.profile like so: export PATH=~/gcc-arm-none-eabi-9-2020-q2-update/bin:~/JLink_Linux_V680b_x86_64:$PATH)

As far as the debugging software is concerned, I first tried using OpenOCD (as you can see from the included debug launch configuration and openocd.cfg file) and it worked for simple flashing and debugging, but started crashing once I set up SWO trace in Cortex-Debug. The error was jaylink_swd_io() failed: JAYLINK_ERR_DEV_NO_MEMORY followed by a USB reenumeration of the probe and numerous other errors; I did not bother troubleshooting the cause (was it because it's running in a VM? who knows...), so I simply switched to SEGGER's official software, which is available and well supported for Linux.

Development utilities

JLink connections (SWD mode)

JLink	Pin	STM32	Pin
VTref	1	3.3V
GND	4	GND
SWDIO	7	PA13	34
SWCLK	9	PA14	37
SWO	13	PB3	39
nRESET	15	NRST	7

Used libraries

• libopencm3
• FreeRTOS

Building

1. Clone repository including submodules

    git clone --recurse-submodules https://github.com/LaXiS96/CaseCommander.git
    cd firmware/
   

2. Build libopencm3 (needed only once after cloning)

    make -C lib/libopencm3
   

3. Build

    make
   

4. Flash

    make flash
   

5. Debug

    # Launch any "Cortex-Debug ..." configuration in VSCode
    # Configurations ending in "... Launch" will flash and reset the MCU; those ending in "... Attach" will simply attach the debugger without flashing nor resetting
   

Useful links

• https://github.com/ve3wwg/stm32f103c8t6
• https://github.com/libopencm3/libopencm3-examples/tree/master/examples/stm32/f1