Greystone Energy Systems · Sensor
CMD5B1 series Modbus carbon monoxide transmitter Modbus register map
Default configuration
- Protocol
- RS485
- Port
- 502
- Unit ID
- 1
- Addressing
- 0-based
- Byte order
- Big endian
- Word order
- High word first
- Baud rate
- 9600
- Parity
- None
- Data bits
- 8
- Stop bits
- 1
This device has an RS-485 interface. Reach it through a Modbus RTU-to-TCP gateway, configured with the factory serial settings above.
Register map
| Address | Count | Name | Type | Unit | Scale | Access |
|---|---|---|---|---|---|---|
| 0 | 1 | CO status Holding register 40001 (offset +0): 0x0000 = CO in normal status, 0x0001 = in abnormal status. | UInt16 | - | 1 | R |
| 1 | 1 | CO value Holding register 40002 (offset +1): unsigned 16-bit CO concentration, 0...500 ppm. | UInt16 | ppm | 1 | R |
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Related guides
Notes
Source: Greystone Energy Systems “Modbus Carbon Monoxide Transmitter – CMD5B1 Series, Installation Instructions”, document IN-GE-CMD5B1XXXMOD-003, vendor-hosted at https://downloads.greystoneenergy.com/Install%20Notes/IN-GE-CMD5B1XXXMOD.pdf. The document fixes the whole line format at the factory (section ‘Modbus protocol’): 9600 bps, 8 data bits, no parity, 1 stop bit, RTU mode, half duplex, CRC-16 (0xA001), and says other parameters are only changed at the factory. The slave address is set with the local DIP switches (1-255) and the document gives no factory switch position; unit 1 is therefore a placeholder, not a cited factory value – set the address your DIP switches select. The map itself is complete: the device exposes exactly two holding registers, status and ppm, read with function code 3; the document's offsets +0/+1 are stored as wire addresses 0 and 1 with zero_based addressing. The transmitter is a parking-garage / IAQ CO sensor (0-500 ppm) and is used for ventilation demand control.