STM32 Microcontroller CAN Bus Communication Comprehensive Analysis: In-depth Explanation of CAN Protocol, Configuration, and Application, Navigating the CAN Bus World

## 1. Basic Concepts of CAN Bus

### Introduction to CAN Bus

The Controller Area Network (CAN) bus is a serial communication protocol designed for high-reliability and real-time applications such as automobiles and industrial automation. The CAN bus has the following features:

- **Multi-master-slave mode:** All nodes connected to the bus can send and receive messages.
- **Non-destructive arbitration:** When multiple nodes try to send messages at the same time, the message with higher priority will gain access to the bus.
- **High reliability:** The CAN bus uses differential signal transmission, which has strong anti-interference capability.

### CAN Bus Protocol

The CAN bus protocol is based on the following key concepts:

- **Frame:** The data transmission unit on the CAN bus, including identifier, data, and checksum.
- **Identifier:** A unique 11-bit or 29-bit number used to identify messages.
- **Data:** The actual data carried by the message, with a length of 0-8 bytes.
- **Checksum:** A 15-bit or 17-bit Cyclic Redundancy Check (CRC) used to detect data errors during transmission.

## 2. STM32 Microcontroller CAN Bus Configuration

### 2.1 Hardware Configuration

#### 2.1.1 CAN Controller Peripheral

The STM32 microcontroller integrates a CAN controller peripheral for managing CAN bus communication. The CAN controller peripheral mainly includes the following registers:

- **CAN_MCR:** CAN bus mode control register, used to configure the operating mode, clock divider, and time trigger of the CAN controller.
- **CAN_MSR:** CAN bus mode status register, reflecting the current operating status of the CAN controller.
- **CAN_TSR:** CAN bus transmission status register, indicating the transmission status of the currently transmitted message.
- **CAN_RF0R:** CAN bus receive FIFO 0 register, used to store received messages.
- **CAN_RF1R:** CAN bus receive FIFO 1 register, used to store received messages.
- **CAN_IER:** CAN bus interrupt enable register, used to enable or disable interrupts generated by the CAN controller.
- **CAN_ESR:** CAN bus error status register, indicating the type of errors that have occurred in the CAN controller.

#### 2.1.2 CAN Bus Interface

The STM32 microcontroller provides a CAN bus interface for connecting to the CAN bus network. The CAN bus interface mainly includes the following pins:

- **CAN_H:** The high-level pin of the CAN bus, connected to the CAN_H line of the CAN bus network.
- **CAN_L:** The low-level pin of the CAN bus, connected to the CAN_L line of the CAN bus network.

### 2.2 Software Configuration

#### 2.2.1 CAN Controller Initialization

The CAN controller initialization process includes the following steps:

1. **Enable CAN clock:** Use the RCC_APB1PeriphClockCmd() function to enable the clock of the CAN controller.
2. **Reset CAN controller:** Use the CAN_DeInit() function to reset the CAN controller and restore the registers to their default values.
3. **Configure CAN controller mode:** Use the CAN_Init() function to configure the operating mode, clock divider, and time trigger of the CAN controller.
4. **Configure CAN filter:** Use the CAN_FilterInit() function to configure the message filtering of the CAN controller.

#### 2.2.2 CAN Message Configuration

The CAN message configuration process includes the following steps:

1. **Allocate CAN message objects:** Use the CAN_FIFO0MessageInit() or CAN_FIFO1MessageInit() function to allocate CAN message objects, which are used to store messages to be sent or received.
2. **Configure CAN message identifier:** Use the CAN_SetTxMessage() or CAN_SetRxMessage() function to configure the identifier of the CAN message.
3. **Configure CAN message data length:** Use the CAN_SetTxMessage() or CAN_SetRxMessage() function to configure the data length of the CAN message.
4. **Configure CAN message data:** Use the CAN_SetTxMessage() or CAN_SetRxMessage() function to configure the data of the CAN message.

## 3. STM32 Microcontroller CAN Bus Communication

### 3.1 CAN Message Transmission

CAN message transmission is one of the core functions of CAN bus communication. The STM32 microcontroller sends CAN messages through the following steps:

- **Initialize the CAN controller:** Before sending messages, the CAN controller must be initialized, including setting the baud rate, timing parameters, and interrupts.
- **Configure the CAN message:** Configure the CAN message to be sent, including the message identifier, data length, and data content.
- **Load the CAN message:** Load the configured CAN message into the CAN transmit buffer.
- **Trigger transmission:** Send a transmission request to the CAN