STM32C5-eval-board

Custom STM32C5 board in the breadboard friendly BluePill format designed in Kicad v10.

Features

• Compact breadboard friendly board size at 53.5mm x 20mm with 2x16 pin headers.
• STM32C551CE Cortex-M33 MCU, 144 MHz, 512 KB flash, 128 KB RAM. (Product page / Datasheet)
• USB-C power connection with CH340E uart to usb bridge (USART1 used).
• LSE 32768 Hz crystal and HSE with 24 MHz crystal.
• 3V3 LDO with power status led.
• Reset button.
• User led and user button.
• SWD header for programming (Must be used as BOOT0 is not exposed).
• All other MCU pins is routed to board edge headers.

Note

This MCU family is quite new and therefore not all variants of this MCU was available with the usual suppliers when this board was created. When other variants with LQFP-48 footprints is available this should be pin compatible with the layout of this board.

Pinout

For complete pin alternative function definitions it is recommended to use the STMicroelectronics application CubeMX2.

Production

Production files adapted to PCBWay recommendations is found in the fab folder.

Firmware

As this is a new MCU family the latest GIT version of stlink is needed to flash this MCU. If this is not available the STMicroelectronics original software can be used. OpenOCD does not yet support this MCU familiy.

In the firmware folder there is a project file for CubeMX2. By opening this file it as matter of generate the CMake project files.

I used VSCode and the CubeMX extension to open the generated CMake project files and added the following test code for a simple blinker application:

/*
  * You can start your application code here
  */

while (1) {
  printf("hello!\n");
  HAL_GPIO_TogglePin(HAL_GPIOB, HAL_GPIO_PIN_9);
  HAL_Delay(2000);
}

Alternative Firmware in Oberon-2

As an alternative to C/C++ the ECSOberon language and the ECSMicroLib framework can be used to develop firmware for this board.

ECSOberon has a number of benefits for MCU applications:

• Simplest possible language (the language report is 20 pages), yet supporting object oriented design with single inheritance.
• The language has the bit SET type which makes fiddling with bit register of the MCU very easy and natural.
• The ECSOberon language is updated with manual allocation, unsigned types, variable pointers, packages and simple templates. Making the language more practical for system programming and MCUs than the original Oberon-2 implementation.
• No header files to worry about. The visibility of the code elements is defined directly in the module.
• The module and package concept keeps the code cleanly segregated and avoid the problem with colliding names in C.
• The documentation is excellent and reported bugs is fixed quickly.

The drawbacks of ECSOberon:

• Oberon-2 is a verbose language and require upper case keyword. However with an IDE and auto-completion this is a minor issue in my opinion.

• No support for a pre-processor. Some cases can be solved with help of templates, but otherwise this must be solved with shell scripts. However this omission keeps the code base readable in my opinion.

• Not much existing code exists and many things must be implemented from scratch. Code from the original OberonSystem 3 or from BlackBox Component Builder could be reused.

  This is the major drawback in my opinion.

Testing

board-testing.webm

The board has been verified to work correctly with the uart-to-usb bridge, leds, buttons and crystals.

Minor issues:

• The SWDIO and SWDCLK pin was swapped.
• The silkscreen was difficult to read.

This will be fixed in a future revision along with any other issue.

TODO

• Fix SWD CLK/DIO swap on silkscreen and schematic.
• Possible expose BOOT0 with a test point on PCB.
• Possible add PCB jumper to disconnect power led for battery operations.
• Review pins used for user button/led and usb-to-uart.

Sponsors

This board was generously sponsored by PCBWay and this project was handled in quick and professional way in my experience. Thanks.

Acknowledgments

This board was developed and with help of and inspiration by the excellent instruction videos on the Phil's Lab Youtube channel.

Also initially skeptical to KiCAD software, it turned out to be a very nice experience working with this application. The team behind KiCAD does an excellent job in turning this application into a professional tool.

License

This project is licensed under the MIT License - see the LICENSE file for details.