Setting Modbus IDs

Like all Modbus devices, Bus Probes connected to the same RS485 bus must be assigned unique Modbus IDs.

Modbus ID of each probe is stored in its register 0x200. IDs must be in the range between 1 and 247. Attempts to set a value outside of this range will be ignored.

Perhaps the most convenient way of setting the IDs of Bus Probes is by using a TPS2(G2) system running one of the two Bus Probe testing apps provided by Tibbo.

Alternatively, you can use any suitable Modbus software to write a new value into the ID register. Since personal computers do not come equipped with RS485 ports, you will need to procure a USB-to-RS485 cable. We successfully tested DigiFusion "FTDI-based" USB-to-RS485 cable. You will also need a DC power source to power the Probes (5~12V voltage range recommended).

It is only possible to alter the ID register when the MD button is pressed*. Therefore, you must press and hold the MD button when sending the write command to your Bus Probe.

* Note: each Bus Probe comes with a metal pin that makes pushing and holding down the MD button easier.

Default Modbus IDs

Default Modbus ID of a Probe depends on the Probe's type:

  • 0x40 for BP#01 (ambient temperature sensor);
  • 0x41 for BP#02 (relative humidity and temperature sensor);
  • 0x42 for BP#03 (ambient light sensor);
  • 0x43 for BP#04 (3-axis accelerometer).