This project demonstrates precise temperature measurement using a K-type thermocouple with the MAX31855 thermocouple-to-digital converter and an STM32F103C6 microcontroller.
The MAX31855 performs cold-junction compensation, digitizes the thermocouple signal, and communicates with STM32 over SPI. The system provides high-resolution temperature readings along with fault detection for improved reliability.
Thermocouples are widely used for their simplicity, ruggedness, and ability to measure a broad temperature range—from cryogenic levels to extreme heat. By integrating the MAX31855 with STM32, this project offers an accurate and efficient industrial-grade temperature sensing solution.
STM32CubeMX Setup- MCU Selection: STM32F103C6 (8 MHz clock)
- SPI1 Configuration:
- Mode: Full-Duplex Master
- Prescaler: 32 (250 kHz clock)
- CPOL: Low, CPHA: 1 Edge
- GPIO Configuration:
- PA4 → Output (Chip Select)
- UART1 Configuration:
- Mode: Asynchronous
- Baud Rate: 9600
- Word Length: 8 bits
- Generate initialization code in STM32CubeIDE.
Key Functions
- Temperature Reading
- float Read_MAX31855_Temperature(void) → Reads thermocouple data and converts to °C
- Fault Detection
- void Check_Faults(uint32_t raw_data) → Detects open thermocouple, shorts, and other errors
- Main Loop
temp = Read_MAX31855_Temperature();
printf("Temperature: %.2f°C\r\n", temp)Required Components
- STM32F103C6 microcontroller
- MAX31855 thermocouple interface
- K-Type Thermocouple
- Virtual Terminal (UART display)
Steps
- Connect SPI lines:
- PA5 → SCLK, PA6 → MISO, PA7 → MOSI, PA4 → CS
- Connect UART1 (PA9 → TX) to Virtual Terminal.
- Connect K-type thermocouple to MAX31855.
- Load the .hex file generated from CubeIDE into Proteus.
- Run simulation → Set thermocouple temperature in component properties.
- Observe measured temperature and fault messages in the Virtual Terminal.
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