How to Build a 16-bit ADC Data Logger with Circular Buffer on STM32F4

Implementing a 16-bit ADC Data Logger with a Circular Buffer on an STM32F4 for Real-Time Temperature Monitoring via I2C

This tutorial will guide you through the process of implementing a 16-bit ADC data logger using a circular buffer on an STM32F4 microcontroller. The data logger will be used for real-time temperature monitoring via the I2C protocol.

Prerequisites

• Basic knowledge of C programming
• Familiarity with STM32 microcontrollers
• STM32 development environment set up (e.g., STM32CubeIDE)
• Temperature sensor with I2C interface (e.g., LM75)
• Basic understanding of ADC and I2C communication

Parts/Tools

• STM32F4 Discovery Board
• Temperature sensor (e.g., LM75)
• Connecting wires
• USB to UART converter (if necessary)
• Multimeter (for testing)

Steps

1. Set Up the Hardware:
   • Connect the temperature sensor to the STM32F4 board using I2C pins (SDA and SCL).
   • Ensure proper power supply to the sensor and microcontroller.
2. Configure the STM32F4:
   • Open STM32CubeIDE and create a new project for your STM32F4 board.
   • Configure the I2C peripheral in the .ioc file:

     
                     // Example configuration
                     I2C_HandleTypeDef hi2c1;
                     hi2c1.Instance = I2C1;
                     hi2c1.Init.ClockSpeed = 100000;
                     hi2c1.Init.DutyCycle = I2C_DUTYCYCLE_2;
                     hi2c1.Init.OwnAddress1 = 0;
                     hi2c1.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT;
                     hi2c1.Init.DualAddressMode = I2C_DUALADDRESS_DISABLE;
                     hi2c1.Init.OwnAddress2 = 0;
                     hi2c1.Init.GeneralCallMode = I2C_GENERALCALL_DISABLE;
                     hi2c1.Init.NoStretchMode = I2C_NOSTRETCH_DISABLE;
                     

   • Enable the ADC module in the .ioc file:

     
                     // Example ADC configuration
                     ADC_HandleTypeDef hadc1;
                     hadc1.Instance = ADC1;
                     hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV4;
                     hadc1.Init.Resolution = ADC_RESOLUTION_12B;
                     hadc1.Init.ScanConvMode = DISABLE;
                     hadc1.Init.ContinuousConvMode = ENABLE;
                     hadc1.Init.DiscontinuousConvMode = DISABLE;
                     hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
                     

3. Implement the Circular Buffer:
   • Define the circular buffer and its size:

     
                     #define BUFFER_SIZE 100
                     uint16_t buffer[BUFFER_SIZE];
                     uint8_t head = 0;
                     uint8_t tail = 0;
                     

   • Implement functions to add and retrieve data from the buffer:

     
                     void add_to_buffer(uint16_t value) {
                         buffer[head] = value;
                         head = (head + 1) % BUFFER_SIZE;
                         if (head == tail) {
                             tail = (tail + 1) % BUFFER_SIZE; // Overwrite oldest data
                         }
                     }
     
                     uint16_t get_from_buffer() {
                         if (head == tail) return 0; // Buffer is empty
                         return buffer[tail++];
                     }
                     

4. Read Temperature Data and Log:
   • Setup the I2C communication to read temperature data:

     
                     uint8_t tempData[2];
                     HAL_I2C_Mem_Read(&hi2c1, LM75_ADDR, TEMP_REG, 1, tempData, 2, 100);
                     int16_t temperature = (tempData[0] << 8) | tempData[1];
                     

   • Log the temperature into the circular buffer:

     
                     add_to_buffer(temperature);
                     

5. Set Up a Timer for Continuous Logging:
   • Configure a timer interrupt to periodically read temperature data.
   • In the timer interrupt callback, read the temperature and log it:

     
                     void TIMx_IRQHandler(void) {
                         if (HAL_TIM_IRQHandler(&htimx) != HAL_OK) return;
                         // Read and log temperature
                         int16_t temperature = read_temperature();
                         add_to_buffer(temperature);
                     }
                     

Troubleshooting

• Sensor Not Responding:
  • Check connections between the STM32 and temperature sensor.
  • Verify I2C addresses and configurations.
• Data Not Logging:
  • Ensure the timer interrupt is set up correctly.
  • Debug the add_to_buffer function to check for buffer overflow or underflow.

Conclusion

By following this tutorial, you have successfully implemented a 16-bit ADC data logger with a circular buffer on an STM32F4 microcontroller for real-time temperature monitoring via I2C. This setup can be further expanded for additional sensors or data processing as needed.