node-red-contrib-seeed-canbus/nodes/can_read.html

Node-RED nodes for Gimbal

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            <option value="none">No Filter (All commands)</option>
            <option value="A4">A4 Commands (Absolute Position)</option>
            <option value="A6">A6 Commands (Absolute Position Legacy)</option>
            <option value="A8">A8 Commands (Relative Offset)</option>
            <option value="94">94 Commands (Status Query)</option>
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    RED.nodes.registerType("can-read", {
        category: "CAN Bus",
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            name: { value: "" },
            client: { value: "", type: "can-config", required: true },
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        outputs: 1, // 1个输出
        icon: "font-awesome/fa-inbox",
        label: function () {
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        paletteLabel: "CAN read",
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# CAN Read

This node continuously listens for CAN messages on the configured interface and outputs them in a standardized format.

## Overview
The node reads CAN bus messages and converts them to a structured format for use in Node-RED flows. It includes support for filtering specific command types, such as absolute position commands (A4), relative offset commands (A8), or status query commands (94).

## Configuration

### CAN Interface
Select the CAN interface configuration to use.

### Command Filter
You can filter which command types the node outputs:
- **No Filter**: Outputs all commands (default)
- **A4 Commands**: Only outputs absolute position commands
- **A6 Commands**: Only outputs legacy absolute position commands
- **A8 Commands**: Only outputs relative offset commands
- **94 Commands**: Only outputs status query commands

## Outputs

The node outputs a message for each relevant CAN frame received:

```json
{
  "payload": "141#c1.0a.64.00.00.00.00.00",
  "details": {
    "id": "141",
    "data": ["C1", "0A", "64", "00", "00", "00", "00", "00"],
    "raw": "C1.0A.64.00.00.00.00.00"
  },
  "timestamp": 1632048172456,
  "topic": "can-message"
}
```

### Output Properties

- **payload** (string): A string in the format "ID#DATA" where ID is the CAN message ID in hexadecimal and DATA is dot-separated hex bytes
- **details** (object): 
  - **id**: CAN message ID in hexadecimal format
  - **data**: Array of bytes in hexadecimal format
  - **raw**: Dot-separated hex string of the data bytes
- **timestamp**: Time when the message was received (milliseconds since epoch)
- **topic**: Set to "can-message"

## Behavior

- The node automatically starts listening for CAN messages when deployed
- It outputs a message for each relevant CAN frame received
- When filtering is enabled, only messages matching the selected command type will be output
- The node status shows the last received message or filter status
- The output format is compatible with the CAN Write node

## Technical Notes

- The node uses a shared channel to communicate with the CAN interface
- The first byte of the data field is used for command type filtering
- If the CAN interface is not available, the node will show an error status

## References

* [GitHub](https://github.com/seeedstudio/node-red-contrib-seeed-canbus) - the nodes github repository
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