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What is inside this frame?

The sensor sent “0B490B0500010501” and the platform shows… nothing. Before blaming the network, read the frame yourself: paste the bytes, pick the sensor, and every value appears with the byte it comes from. Ready? Let’s go!

A quick reminder before we start

A decoded LoRaWAN frame is a sequence of bytes, and every sensor arranges them its own way: two bytes for the battery voltage in millivolts, two for the distance in millimetres, one for a flag… A codec is nothing more than that layout table. Here we describe it in one line: bat:u16@0/1000#V means “the field bat is a 16-bit unsigned integer starting at byte 0, divided by 1,000, in volts”.

One field per word: name:type@byte[/divisor][#unit]

The grammar in 30 seconds

Types: u8 i8 u16 i16 u24 u32 i32 f32 (big-endian; append l for little-endian: u16l, f32l). @ position of the first byte, from 0. / optional decimal divisor. # optional unit. A field beyond the frame is simply skipped.

Spaces and 0x prefixes accepted. This is the application payload, already decrypted by the network.

Example frames

Bytes

Decoded values

FieldValueUnitBytes
Paste a frame to start.

The trap

The same sensor sends several layouts depending on the port (FPort): the measurement frame on port 2, the device status on port 5, the datalog on port 3. Decoding a status frame with the measurement codec gives plausible… and wrong values. Always check the port before blaming the sensor.

The right setting

When a value is absurd (a temperature of 3,276.7 °C, say), it is almost always a sentinel: 0x7FFF for “no probe”, 0x0000 for “sensor missing”. The manufacturer documents them in the manual; each codec’s limits are recalled under the result.

In short

  • A frame = bytes; a codec = the table that says where each value is.
  • Check the FPort before decoding: a sensor has several layouts.
  • Absurd value = sentinel, not a failure.
  • The one-line layout can be pasted as is into an Awaro gateway.

Your sensor is not in the list? Describe its layout in one line and send it to us: it will join the database.

Codecs and grammar: open database lorawan2mqtt/codecs (format importable into the Awaro gateway).

Missing a tool?

Tell us what you are trying to do: if we already have it on the bench, we will put it online.

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