Abstract:

This video tutorial demonstrates the implementation of the SPI communication protocol on a CH32V003F4P6 microcontroller using the MounRiver Studio IDE. The practical application involves interfacing with an ADXL345 3-axis accelerometer, covering detailed setup of GPIO pins and SPI peripheral in master mode, along with the development of custom functions for register read/write operations tailored to the sensor's datasheet. The tutorial culminates in reading and displaying real-time acceleration data, including a unique method for printing pseudo-floating-point values, and visualizing the sensor's output graphically using Arduino's Serial Plotter.

Summary:

• 0:00 Introduction & Demo Setup: The video continues a CH32 tutorial series, focusing on the SPI protocol, demonstrated using an ADXL345 3-axis accelerometer wired for 4-wire SPI (Chip Select, MOSI, MISO, SCLK). The setup utilizes a CH32V003F4P6 microcontroller, programmed with a debugger module via SWIO, and communicates with a PC via UART. Software development occurs in MounRiver Studio v2.
• 3:42 ADXL345 Sensor & SPI Advantages: The ADXL345 sensor communicates via SPI or I2C; SPI is chosen for its higher speed, full-duplex (simultaneous two-way) communication, and dedicated chip select pin that avoids I2C address conflicts.
• 8:19 SPI Initialization: The SPI_Initialize function is set up, configuring GPIO clocks and pins for Chip Select (PC4, output push-pull, initially high), SCLK (PC5, alternative function push-pull), MOSI (PC6, alternative function push-pull), and MISO (PC7, input floating). SPI1 is configured as a master, 2-lines full duplex, 8-bit data, high clock polarity, 2nd edge clock phase, software chip select management, 1.5MHz bus speed, and MSB first.
• 16:59 SPI Transfer Function: The SPI_Transfer function is implemented to send a byte and simultaneously receive a byte, enabling the full-duplex communication necessary for SPI.
• 19:11 Register Read/Write Operations:
  • ADXL345_WriteRegister handles manually pulling the Chip Select pin low before data transfer and high afterward, then sends the register address and value.
  • ADXL345_ReadRegister demonstrates constructing a command byte by combining the register address with read (D7) and multi-byte (D6) bits based on the datasheet. It then transfers this command and subsequent dummy bytes to receive data into a buffer.
• 27:26 Chip Initialization & Verification: The ADXL345_Initialize function configures the sensor's power control (measurement mode), data format (4-wire SPI, full resolution, +/-2G range), and data rate (3200Hz). Communication is verified by reading the DEVICE_ID register (expected 0xE5).
• 34:30 Communication Confirmation: The tutorial demonstrates successful chip recognition by displaying the expected DEVICE_ID value (229 or 0xE5) in the MounRiver Studio's serial terminal.
• 34:50 Reading Acceleration Data: The ADXL345_ReadAcceleration function reads 6 bytes of acceleration data from the sensor, using its multi-byte read feature. The received 8-bit low and high bytes are then combined into 16-bit signed integers for X, Y, and Z axes.
• 39:17 Pseudo-Floating-Point Output: A custom PrintAcceleration_g function is created to display acceleration values in 'G' units as pseudo-floating-point numbers on the microcontroller, which lacks native float support. It achieves this by scaling the raw data and extracting whole and fractional parts for printing.
• 44:26 Real-time Visualization: Real-time X, Y, Z acceleration data is visualized in both the MounRiver Studio terminal and, more impressively, using Arduino IDE's Serial Plotter.
• 45:06 Sensor Demonstration: Tilting the accelerometer is shown to dynamically change the X, Y, and Z G values, demonstrating the sensor's responsiveness.
• 47:26 Additional Sensor Capabilities & Resources: The video briefly discusses other ADXL345 features like tap detection (useful for triggering microcontroller wake-up) and highlights its application in high-speed vibration analysis for maintenance and failure detection. Code (main.c file) is available on GitHub and a related article on the presenter's website.