【Hardware Peripheral Use】——SPI

SPI basic concept

SPI is a serial port communication interface, which is a synchronous full-duplex protocol for transferring data between digital circuits. SPI stands for Serial Peripheral Interface, which is a very popular digital communication interface, especially suitable for use in embedded systems and microcontrollers.

The SPI bus consists of the following main parts:

1. Master device: The master device is usually a chip, a microcontroller or a single-chip microcomputer, and its task is to control data transmission and control the read and write operations of the slave device.

2. Slave: A slave is a peripheral, such as a memory, sensor, or other chip, connected to a master.

3. Clock Line: The clock line is a synchronous clock signal controlled by the master device to synchronize data transfers.

4. MOSI line: The MOSI (Master Output Slave Input) line is the data line for the master device to send data to the slave device.

5. MISO Line: The MISO (Master In Slave Out) line is the data line through which the slave sends data back to the master.

6. SS line (slave select): The SS line is used to select the slave device, which is controlled by the master device.

The transmission speed of the SPI protocol is very high, usually greater than 1Mbps, and it can transmit a large amount of data at high speed in a short time. The SPI protocol is also very flexible and can support the connection of multiple slave devices, and its performance and parameters can usually be modified through configuration.

The SPI protocol is often used for the control of various peripheral devices, such as sensors, memories, A/D converters, LCD screens, etc.

SPI communication protocol

The SPI communication protocol is a serial communication protocol used to transfer data between digital circuits.
There is one master device and multiple slave devices in the SPI communication protocol, and all devices share the same data bus. The master device controls the clock line, selects the slave device, and sends data to the slave device; and the slave device sends data back to the master device through the MISO line after receiving the selection signal from the master device.

The characteristics of the SPI communication protocol are:

1. Fast speed: The transmission rate of the SPI communication protocol can reach hundreds of Kbps to several Mbps.

2. Good flexibility: Its performance and parameters can be modified through configuration, and it supports one-way or two-way data transmission, etc.

3. Support multiple slave devices: SPI communication protocol can connect multiple slave devices, but each slave device must have its own unique chip select signal.

4. Short transmission distance: The transmission distance of the SPI communication protocol is relatively short, generally no more than a few meters.

The basic communication process of the SPI communication protocol is as follows:

1. The master device sends a chip select signal to the slave device to select the slave device to communicate with;

2. The master device sends a clock signal to the slave device and starts to transmit data;

3. The master device sends data to the slave device, and the slave device sends the data back to the master device through the MISO line;

4. After the master device completes the transmission, it sends a chip select signal to the slave device to complete this communication.

The SPI communication protocol is a low-cost, high-speed, and simple communication protocol, which is widely used in sensors, memory chips, display modules and other devices.

How to use SPI

pyb.spi

pyb.spi is the SPI module in MicroPython, which is used to set and control the SPI bus on the MCU for data transmission. Through this module, you can easily access the SPI interface and read and write SPI devices.

The pyb.spi module provides the following important functions:

1. init(): Initialize the SPI bus, you can set the clock frequency, master-slave mode, data bit width and other parameters.

2. send(): Send data to SPI device.

3. recv(): Read data from SPI device.

4. send_recv(): Simultaneously send and receive data to and from the SPI device.

5. readinto(): Read data from SPI device and store into buffer.

6. write(): Write data to SPI device.

7. write_readinto(): Simultaneously write and read data to and from the SPI device.

In addition to the above functions, the pyb.spi module also provides some other useful functions and properties, such as getting or setting the SPI clock frequency, setting the SPI data to high-impedance state, selecting the SPI slave device, etc.

machine.spi

The machine.spi module is not designed for a specific brand of development board, but a general-purpose SPI module that can be applied to many different hardware platforms.

The machine.spi module provides the following important functions:

1. init(): Initialize the SPI bus, you can set the clock frequency, master-slave mode, data bit width and other parameters.

2. write_readinto(): Simultaneously write and read data to and from the SPI device.

3. readinto(): Read data from SPI device and store into buffer.

4. write(): Write data to SPI device.

In addition to the above functions, the machine.spi module also provides some other useful functions and properties, such as getting or setting the SPI clock frequency, setting the SPI data to high-impedance state, selecting the SPI slave device, etc.

SPI Available Sensors

SPI bus is a commonly used serial communication protocol widely used in various digital sensors, memories and other peripherals. The following are some common sensors available with SPI interface:

1. ADXL345: Three-axis accelerometer

2. LIS3DH: Three-axis accelerometer

3. MPU6050: Six-axis gyroscope and accelerometer

4. LSM9DS1: Nine-axis Inertial Measurement Unit (IMU)

5. BMP280: Barometric pressure and temperature sensor

6. MCP3008: 8-way 12-bit analog-to-digital converter (ADC)

7. MAX31865: Thermocouple Amplifier

8. ENC28J60: Ethernet Controller

9. W5500: Hardware TCP/IP protocol stack

10. MCP2515: CAN Controller

11. AS5040: Rotary Encoder

12. HX711: Load Cell Amplifier

The above are some common sensors that can be accessed through the SPI interface, but the SPI interface is not only used for sensors, but can also be used to control various other peripherals.

When choosing a sensor using the SPI interface, it is necessary to consider factors such as the performance, price, operating temperature range, power supply voltage, and signal accuracy of the chip itself, and choose a product suitable for the specific application.