The serial communication protocol document indicates automatic threshold determination can be achieved with command 0x0009 but does not explain the meaning of the command values. How should "trigger factor", "retention factor" and "scanning time" be chosen? How do they affect the result?
2 Answers
Command Word: 0x0009
This is the unique identifier for this specific command.
The command value contains three parameters:
Trigger Factor: 00 02
- Format: Little-endian (low byte first, high byte last).
- Actual Value: 0x0200 = 512 (decimal).
- Purpose: Controls the trigger sensitivity after the radar detects a target.
- A higher value results in lower sensitivity (requiring a stronger signal to trigger).
Hold Factor: 00 01 - Actual Value: 0x0100 = 256 (decimal).
- Purpose: Controls the duration for which the radar maintains the "target detected" state after the target has disappeared.
- A higher value results in a longer hold time.
Scan Time: 00 78 - Actual Value: 0x7800 = 30720 (decimal).
- Purpose: Controls the duration of the environmental scan performed by the radar.
- Unit: Typically milliseconds (ms).
Data Frame Format
| Frame Header | Data Length | Command Word | Trigger Factor | Hold Factor | Scan Time | Frame Footer |
|---|---|---|---|---|---|---|
| FD FC FB FA | 08 00 | 09 00 | 02 00 | 01 00 | 78 00 | 04 03 02 01 |
Return Value Description
Return Value: 2 bytes (Progress * 100)
- Example: If the return value is 5000, it indicates a progress of 50%.
Return Data Format
| Frame Header | Data Length | Data Type | Threshold Generation Progress | Frame Footer |
|---|---|---|---|---|
| F4 F3 F2 F1 | 2 bytes | 0x03 | 2 bytes (Progress * 100) | F8 F7 F6 F5 |
Usage Recommendations
- The automatic threshold update feature is suitable for use in environments with significant changes, as it allows the radar to adapt automatically to the current environment.
- The Trigger Factor and Hold Factor should be adjusted according to the specific application scenario.
- A longer scan time results in more accurate auto-calibration, but it also takes more time.
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This is not accurate! The scan time is in seconds and the return value is % (it ends with value=100 not 10000). And the explanation of the trigger factor is confused with the trigger threshold. Also actual value for scan time would be 0x0078 = 120 decimal, whereas 0x7800 is the litte-endian formatted byte pair to send in the command.
So: the meaning of the "factor" parameters is still unclear, but I can confirm that the scan time is in seconds (the software tool requires a minimum of 120 decimal) and the progress value is a percentage. Command mode should be exited (cmd=0x00fe) before listening for progress messages.
The deepseek answer is obviously inconsistent with the software tool and LD2410S protocol document and within the answer. The units of time are wrong, the range of the factors is wrong. Absolutely no use at all!