SHT30 Temperature/Humidity Sensor
The SHT30 sensor is available with options that include either an I2C or RS485 interface. The present exercise, however, is part of developing a broader understanding of the characteristics of RS485 communications, although it will also provide a direct comparison between the general requirements for and operation of these two connectivity options.
The basic operational details were provided on the AliExpress product page.
To date, I have referred to manuals for similar sensors, this one and this one, retrieved from the ComWinTop website, as a guide in forumlating the necessary Modbus RTU queries.
Testing Notes
- The sensor specifications indicate that it will operate with a supply voltage of 5~30V although some documentation suggests that the sensor itself operates on a voltage of 2.4~5V. In the event, it responded to Modbus RTU queries reliably and reported plausible ambient temperature readings on a 5V supply from the [USB powered] CubeCell Plus.
- Supplied with a default baud rate setting of 9600.
- Responds to a Modbus RTU broadcast address of 0x00.
- As supplied, when queried this sensor reports a Slave ID of 0x00, even though all of its responses show a source Address of 0x01. It does, however, respond to queries directed to a Slave ID of 0x01—it also responds to queries directed to a Slave ID of 0x00, but this, of course, is also the address it would recognise as the broadcast address. Regardless, I was unable to change the Slave ID. The sensor would respond to the query, but simply report that its Slave ID was 0x00, rather than reflecting the requested change. It may be that I am doing something wrong here, but I am following the same process that I used to successfully change the Slave ID of the Soil Condition sensor.
Further details pending