tiny-manager - Microcontroller firmware for baseboard management

tiny-manager will, one day, become a general purpose firmware for baseboard management.

Currently however is a single purpose firmware that can toggle the power and reset lines for the STM32F042 found on the Solidrun Honeycomb LX2. Nevertheless this is sufficient to be a proof-of-concept showing how to squeeze a simple USB ACM command processor into the tiny, tiny flash of the STM32F042. Now we have working USB then how hard can the rest of it really be ;-) !

Quickstart

• Install the Arm Embedded
  Toolchain
  (or similar arm-none-eabi- compiler) and dfu-util.
• Clone this repo:
  git clone https://github.com/daniel-thompson/tiny-manager.git
• Fetch the libraries:
  cd tiny-manager; git submodule update --init --recursive
• Build the firmware:
  make
• Use the jumper link to force the Micro-BMC on the Honeycomb to DFU
  mode and power up the board:
  make -C src/stm32f0-relay flash
• Unset the jumper and cycle the power.

Usage

The firmware registers itself as a CDC-ACM device and, under Linux, will be presented as ttyACMx where x is typically 0 on "simple" setups although will be larger if there is any USB communication or modem device installed (for example an unused 3G modem).

Type help to get a list of available commands.

• echo - test command that echos back its input
• help - shows a list of commands
• power - manipulate the power line (hold it on for 7 seconds to
  for a power off)
• reset - manipulate the reset line, note that the BMC reset line
  does not work correctly on early Honeycomb boards (due to an
  incorrectly designed combination of bidirectional level shifters
  and current limiting resistors) meaning the reset command may not
  work on all boards.

udev rules

Note: This section is aspirational... but hopefully it will be implemented soon.

The firmware uses the STM32 unique device ID to provide every physical instance with a unique serial number. This allows udev rules to be introduced to ensure stable device enumeration regardless of any changes to the USB topology.

SUBSYSTEM=="tty", ATTRS{manufacturer}=="redfelineninja.org.uk", ATTRS{serial}=="045101780587252555FFC660", SYMLINK+="ttyrelayC660"
SUBSYSTEM=="tty", ATTRS{manufacturer}=="redfelineninja.org.uk", ATTRS{serial}=="7301C2152B72E52DE2744F3B", SYMLINK+="ttyrelay4F3B"

The serial number can picked up from the kernel log (dmesg) or using udevadm: udevadm info --attribute-walk /dev/ttyACM0 | grep serial .

udevadm can also be used to re-apply the rule if any changes are made to the symlink: sudo udevadm trigger /dev/ttyACM0