An STM32-based development board for boundless exploration in Embedded Systems.
Introducing the STM32PlayBoard. As the name suggests, the main object of developing this board is to expand my knowledge and provide an entry gate for others to learn Embedded Systems with a well-known and documented microcontroller by STMicroelectronics.This project opens the door to immersive learning experiences and practical experimentation.
A Catalyst for Growth and Innovation, the reason for the development of STM32PlayBoard was rooted in a dual ambition: to push the boundaries of my expertise in PCB design while creating a versatile tool that resonates with my journey in Embedded Systems.
- Elevating PCB Design Expertise: This project moved me into a relatively complex PCB design I was familiar with. It also provided a stage to experiment with diverse PCB manufacturing and assembly services, broadening my understanding of the complexities of hardware production.
- Fulfilling a Learning Trip: While learning about ARM Cortex-M architectures, I have always used a variety of STMicroelectronics boards. Recently, I wanted to develop a basic yet peripheral-rich custom board.
I pictured a compact design for the STM32PlayBoard that prioritized accessibility to a wide range of communication protocols while offering dedicated pins for ADC, timers, and some general-purpose I/Os.
This careful pin allocation aimed to balance versatility, functionality, and ease in PCB designing. By providing exposure to commonly used communication interfaces and essential GPIO options, the board becomes an adaptable platform for various applications.
Additionally, the compact nature of the design wasn't just about efficient use of space; it also served a practical purpose. I aimed to create a development board that could seamlessly integrate into my other projects as a convenient replacement. This design approach allows for easy adaptability across different projects, simplifying development and minimizing the need for significant redesigns.
- The board's core is an STM32F103C8T6 microcontroller from STMicroelectronics, running with a 16MHz High-Speed External Oscillator.
- Board has a configurable BOOT0 for different operational modes.
- A physical reset button for manually resetting the board.
- The board can be powered by an external voltage supply and through Micro B USB. They are reverse polarity protected and can both coexist.
- The voltage regulation is accomplished using AMS1117-3.3 linear voltage regulator from Advanced Monolithic Systems. Since the main component on the board is the main microcontroller IC, I went with this standard, less expensive, and easily available LDO.
- The maximum voltage that can be provided externally is 18V, and the maximum drop-out voltage of this LDO is 1.2V at 1A. We are going to be far from this current consumption using this board.
- The Silkscreen on the back side of the PCB shows 15V is just an additional safety measure (not to exceed 15V even though up to 18V is acceptable).
- The board supports USB 2.0 full-speed interface using a Micro B connector.
- The board provides ESD protection on USB using USBLC6 IC from STMicroelectronics.
- D3 is onboard status LED and is connected to pin PA1. The cathode of the LED is permanent ground.
- D2 is the Power LED indicating a healthy power supply.
- The PCB is two layered board. The reason for being two layers is I wanted to go with a simple board design, which also minimizes the production cost.
- The entire bottom layer of the board is grounded, and the Top layer is the signals layer.
- A wide trace of 0.5mm is for power, and a 0.3mm trace is for signals.
- The board dimensions are 56x36mm.
- This board functions as a development board with GPIO and communication protocols exposed.
The board exposes:
- 1 SPI connection (SPI1)
- 1 I2C connection (I2C2)
- 1 USART connection (USART1)
- SWD for programming and debugging
- 1 ADC (ADC1_IN0)
- 2 timers (TIM1_CH1 and TIM1_CH2)
- 4 GPIOs from Port B (PB3, PB4, PB5, PB6)
- An onboard LED on pin PA1
- The voltage level for all the pins is 3.3V. And for interfacing with other 5V level compatible boards (for example, Arduino), a logic level shifter/converter is required.
The board can be programmed using an external ST-Link programmer via the SWD interface.
| Input Voltages | Max Values |
|---|---|
| Through USB connector | 5V |
| Through Power connector | 18V |
| GPIO Tolerances | Max Values |
|---|---|
| All pins | 3.3V |
| Memories | Size |
|---|---|
| FLASH | 64 Kbytes |
| SRAM | 20 Kbytes |
| Exposed Peripherals | Connected to |
|---|---|
| I2C2_SDA | PB11 |
| I2C2_SCL | PB10 |
| USART1_RX | PB7 |
| USART1_TX | PB6 |
| SPI1_NSS | PA4 |
| SPI1_SCK | PA5 |
| SPI1_MISO | PA6 |
| SPI1_MOSI | PA7 |
| Status LED D3 | PA1 |
| ADC1_IN0 | PA0 |
| TIM1_CH1 | PA8 |
| TIM1_CH2 | PA9 |
| GPIO1 (USART1_TX) | PB6 |
| GPIO2 | PB5 |
| GPIO3 | PB4 |
| GPIO4 (SWO) | PB3 |
Throughout the development of this board, I discovered a lot regarding designing a PCB with a microcontroller on it and various design practices like decoupling and bulk capacitors. I also wanted to learn to program a STMicroelectronics microcontroller using an external programmer, and I achieved this using this board.
As per software development skills, I am writing my drivers for various peripherals and example codes for this board, which are available on this GitHub repository.
Keeping this project as a base, I would like to design and develop another STM32-based development board with a different, more powerful microcontroller with various onboard peripherals like FLASH memory and some onboard sensors communicating with the main IC using multiple communication protocols.