Value transforms

Gateways often send values that need a small fix before they're useful: a register that reads 2314 when it means 231.4 V, a number sent as text, or a state sent as the word RUN. Value transforms fix these in the mapping, without writing code.

Who can do this: Admin User

Add a transform

1. In the mapping step, find the mapping row.
2. Click Transform value under the JSON Path to open it.
3. Fill in what you need. Every field is optional.
4. Click Test Mapping to check the result against your sample.

The steps always run in this order: Convert, then Multiply by, then Then add, then Round to decimals.

Convert

Option	Does	Example
None	Nothing.
Text → number	Turns text into a number. Understands units and commas.	"230 V" → 230, "22,5" → 22.5, "1,234.5" → 1234.5
On/Off → true/false	Turns words into true or false.	ON, yes, run, open, active, high, 1 → true. OFF, no, stop, closed, inactive, low, 0 → false
One bit of a register	Reads one bit of a number. Enter the Bit number, where 0 is the lowest.	Status register 6, bit 1 → 1
Map values	Replaces values from a list. Enter Values as FROM=TO pairs. A value not in the list is stored empty.	RUN=1, STOP=0, FAULT=2
Read from bytes	Reads a number out of raw bytes (hex text or a list of bytes). Choose the Byte type and Byte offset (0 is the first byte).	For LoRaWAN sensors without a decoder

Byte types for Read from bytes: unsigned or signed 8-bit; unsigned or signed 16-bit or 32-bit, big-endian or little-endian; and 32-bit float, big-endian or little-endian. Your device's datasheet says which one to use. "Big-endian" means the most significant byte comes first, which is the usual choice for Modbus.

Scale and round

Field	Does	Example
Multiply by	Multiplies the value. Use a decimal to divide.	0.1 turns 2314 into 231.4
Then add	Adds to the value. Use a minus sign to subtract.	-273.15 turns Kelvin into °C
Round to decimals	Rounds to this many decimal places.	1 turns 231.4567 into 231.5

Examples

Gateway sends	You want	Set
"voltage_raw": 2314	231.4	Multiply by 0.1
"temp": "22.5 C"	22.5	Convert Text → number
"pump": "RUNNING"	true	Convert On/Off → true/false
"state": "FAULT"	2	Convert Map values, RUN=1, STOP=0, FAULT=2
"status": 5, bit 2 is "door open"	1	Convert One bit of a register, Bit number 2
"energy_wh": 123456	kWh, 2 decimals	Multiply by 0.001, Round to decimals 2

Written as text

Transforms are stored at the end of the JSON Path, after a |. You can also type them there directly:

voltage_raw | multiply:0.1 | round:1
bytes | int16be:0 | multiply:0.01
state | map:RUN=1,STOP=0

If you type steps in another order, or use divide or subtract, the panel shows them as Custom steps and you edit them in the path instead.

Common problems

"Unknown transform: …. This value will be stored empty." A step name is misspelled. Fix it in the JSON Path.

Test Mapping says "The transform gives no value for the sample." The conversion couldn't read the value, for example Text → number on text with no number in it, or Read from bytes past the end of the frame. Check the byte offset and type.