Colead SL-5868P
The Colead SL5868P is an inexpensive sound level meter with RS232 capability. It has Lp and Leq measurement modes, and can trigger alarm conditions based on a configured level.
It is rebranded under many names, but appears to generally have the SL-5868P model designation. It's available for under $100.
Hardware
- Nuvoton W78E052D 8-bit microcontroller
- Holtek HT1621B LCD driver
Photos
Protocol
TODO: serialcomm
The meter sends two measurements per second. When a new measurement is ready, the device sends 0x10. The PC responds with 0x20, which causes the device to transmit a 10-byte structure containing configuration and measurement.
Commands
| Command | Direction | Description |
|---|---|---|
| 0x10 | Device -> PC | Measurement ready |
| 0x20 | PC -> Device | Send measurement |
Data structure
| Byte | Value | Description |
|---|---|---|
| 0 | Always 0x08 | |
| 1 | Always 0x04 | |
| 2 | Configuration. The low nibble has the following meaning: | |
| 0000 | Lp, Weighting A, Fast | |
| 0001 | Lp, Weighting A, Slow | |
| 0010 | Lp, Weighting C, Fast | |
| 0011 | Lp, Weighting C, Slow | |
| 0100 | Lp, Flat, Fast | |
| 0101 | Lp, Flat, Slow | |
| 0110 | Ln, Weighting A, Fast | |
| 0111 | Ln, Weighting A, Slow | |
| 1000 | Leq, Weighting A, Fast (10-second mean) | |
| 1001 | Leq, Weighting A, Fast (mean over minutes) | |
| 1010 | Leq, Weighting A, Slow (10-second mean) | |
| 1011 | Leq, Weighting A, Slow (mean over minutes) | |
| 1100 | Internal calibration mode, Fast | |
| 1101 | Internal calibration mode, Slow | |
| 1110 | Unused | |
| 1111 | Unused | |
| The high nibble has the following meaning: | ||
| 0001 | Normal measurement | |
| 0010 | Max hold mode | |
| 3-7 | BCD-encoded value, one byte per digit 0x00-0x09. 0x0a means ignored digit. The last digit represents the decimal. | |
| 8 | Measurement status | |
| 0 | Invalid | |
| 1 | Valid | |
| 9 | Checksum: sum of bytes 0-8 |