Usb4All with Cortex M3 (STM32F103C8) or M4 (GD32F303CC)

My new project is a Cortex M3 based board in year 2020, and I will fresh this page, when there is any news later. The plan is that this board will be compatible with the older PIC18F2550 based panel.

I think, the circuit is ready. The peripheries has extended with a temperature sensor (DS18B20), and some usefull parts i.e. battery connection, SPI connection for SD-card pinout, I2C connection for BME280 barometer panel, reset jumper, TPS3813 heartbeat circuit (not tested yet) and Blue Pill compatible SWD pinout and PC13 LED.

The firmware is not ready yet, but many features work: FreeRTOS based process management, LCD display, STM32 internal rtc, temperature sensor, PWM for display backlight, UART communication, heartbeat signal and 4 buttons handle. I have to write and implement the USB, I2C and SPI divers and peripheries.

I have written I2C functions yet, so I bulit two different version barometers with this board. The barometer sensor is the Bosh BME280. The third board has a DS18B20 sensor, wich can measure the temperature only. Sadly the accuracy is not too precise, as you can see on the photo.

But the flourescent display is really nice!

Two seemingly same board are on the right side of this article.

But the upper board has a STM32F103C8 (Cortex M3) microcontroller, and the lower has a GD32F303CC (Cortex M4). Because the stm32 (ST) and gd32 (Gigadevice) mcu-s have pin and functional compatibilty, I had to implement only the software interface for successful exchange. I finished this work during this winter vacation (2023-2024).