STM32F103CB Study Board

This is a playground project created around an STM32F103C6T8 "study board" sourced from ebay.

To Do next

• RTC for time keeping, but the board has no battery back up :-(
• USB
• UART
• I2C using DMA. presently bit-banged.

PCB

Name and URL on backside LC Technology
link in English ARM Cortex-M3 STM32F103C8T6 Dev board Core Board
Link in Chinese STM32F103C8T6开发板 STM32 核心板 开发板

STM32-base lists similar looking boards with other CPUs and other boards with the STM32F103C8T6, but not this combination. The "MINI STM32 Schematic Diagram" from Open Impulse appears to match

Project build

The base project was created using ST's CubeMX with LL divers for everything except USB.
Compiler/IDE is IAR EWARM 7.8

TM1637 support

I2C-like support for a TM1637 is implemented using bit-banged I/O. CLK = PB066 DIO = PB07 The original source is from https://github.com/rogerdahl/stm32-tm1637 The code has been modified in several ways:

• I/O is mapped to I2C1 pins on STM32F103C8T6.
• use uSecDelay() for uSec delays. This function uses the SysTick counter for accurate timing.
• IC2 CLK is push-pull, I2C data is push-pull for all cycles except during ACK from TM1637.
• ACK is checked as part of byte write function.
• return ACK status (presently ignored.)
• made brightness a variable, fixed an issue with the initial setting.

commit notes

04/22/2022 MAR

• systick is running at 1mS. Main loop sleeps until SysTick changes.
• UART with basic echo: implemented with IRQs.
• TM1637 is working, toggling colon every 500mS and updating the displayed count every second.

03/15/2023 MAR

• update links to PCB info.
• fix project to use local copy of TM1637 driver.