wanckl
164 lines
4.4 KiB
Markdown
164 lines
4.4 KiB
Markdown
| Supported Targets | ESP32 | ESP32-C3 | ESP32-C5 | ESP32-C6 | ESP32-H2 | ESP32-P4 | ESP32-S2 | ESP32-S3 |
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| ----------------- | ----- | -------- | -------- | -------- | -------- | -------- | -------- | -------- |
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# TWAI Network Example
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This example demonstrates TWAI (Two-Wire Automotive Interface) network communication using the ESP-IDF TWAI driver. It consists of two programs that showcase different aspects of TWAI bus communication.
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## Overview
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### Programs
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- **twai_sender**: Sends periodic heartbeat messages and large data packets
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- **twai_listen_only**: Monitors specific message ID using a filter
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### Key Features
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- Event-driven message handling with callbacks
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- Message filtering using acceptance filters in listen-only mode
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- Single/Burst data transmission and reception
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- Real-time bus error and node status reporting
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## Hardware Setup
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### Wiring
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For multi-device testing:
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1. Connect TWAI transceivers to each ESP32xx
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2. Wire TWAI_H and TWAI_L between all devices using line topology
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3. Add 120Ω termination resistors at both ends of the bus
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For single-device testing, enable self_test mode in the sender.
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### GPIO Configuration
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The GPIO pins can be configured using menuconfig:
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```bash
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idf.py menuconfig
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```
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Navigate to: `Example Configuration` → Configure the following:
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- **TWAI TX GPIO Num**: GPIO pin for TWAI TX
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- **TWAI RX GPIO Num**: GPIO pin for TWAI RX
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**Default configuration:**
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```c
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#define TWAI_TX_GPIO GPIO_NUM_4
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#define TWAI_RX_GPIO GPIO_NUM_5
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#define TWAI_BITRATE 1000000 // 1 Mbps
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```
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## Message Types
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| ID | Type | Frequency | Size | Description |
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|----|------|-----------|------|-------------|
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| 0x7FF | Heartbeat | 1 Hz | 8 bytes | Timestamp data |
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| 0x100 | Data | Every 10s | 1000 bytes | Test data (125 frames) |
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## Building and Running
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### Build each program (sender, listen_only):
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**Enter the sub-application directory and run:**
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```bash
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idf.py set-target esp32 build flash monitor
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```
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## Expected Output
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### Sender
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```
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===================TWAI Sender Example Starting...===================
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I (xxx) twai_sender: TWAI Sender started successfully
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I (xxx) twai_sender: Sending messages on IDs: 0x100 (data), 0x7FF (heartbeat)
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I (xxx) twai_sender: Sending heartbeat message: 1234567890
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I (xxx) twai_sender: Sending packet of 1000 bytes in 125 frames
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```
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### Listen-Only Monitor
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```
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===================TWAI Listen Only Example Starting...===================
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I (xxx) twai_listen: Buffer initialized: 200 slots for burst data
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I (xxx) twai_listen: TWAI node created
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I (xxx) twai_listen: Filter enabled for ID: 0x100 Mask: 0x7F0
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I (xxx) twai_listen: TWAI start listening...
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I (xxx) twai_listen: RX: 100 [8] 0 0 0 0 0 0 0 0
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I (xxx) twai_listen: RX: 100 [8] 1 1 1 1 1 1 1 1
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```
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## Implementation Details
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### Message Buffering
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Each program uses a buffer pool to handle incoming messages efficiently:
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- **Sender**: Small buffer for transmission completion tracking
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- **Listen-Only**: 100-slot buffer for monitoring filtered traffic
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### Operating Modes
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- **Normal Mode** (Sender): Participates in bus communication, sends ACK frames
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- **Listen-Only Mode** (Monitor): Receives filtered messages without transmitting anything
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### Message Filtering
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The listen-only monitor uses hardware acceptance filters to receive only specific message IDs:
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```c
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twai_mask_filter_config_t data_filter = {
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.id = TWAI_DATA_ID,
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.mask = 0x7F0, // Match high 7 bits of the ID, ignore low 4 bits
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.is_ext = false, // Receive only standard ID
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};
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```
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### Error Handling
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- Bus error logging and status monitoring
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## Configuration
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### Customizing Buffer Sizes
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Adjust buffer sizes in each program as needed:
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```c
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#define POLL_DEPTH 200 // Listen-only buffer size
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```
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### Changing Message IDs
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Update the message ID definitions:
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```c
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#define TWAI_DATA_ID 0x100
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#define TWAI_HEARTBEAT_ID 0x7FF
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```
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## Use Cases
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This example is suitable for:
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- Learning TWAI bus communication
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- Testing TWAI network setups
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- Developing custom TWAI protocols
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- Bus monitoring and debugging
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- Prototyping automotive communication systems
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## Troubleshooting
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### No Communication
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- Check GPIO pin connections
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- Verify bitrate settings match between devices
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- Ensure proper bus termination
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### Buffer Overflows
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- Increase buffer size (`POLL_DEPTH`)
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- Reduce bus message transmission rate
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- Optimize message processing code
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### Bus Errors
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- Check physical bus wiring
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- Verify termination resistors (120Ω at each end)
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- Monitor error counters with `twai_node_get_info()`
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