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ble read

Reads a characteristic of another Bluetooth LE device for each message that arrives, and sends the value on.

Properties

  • BLE peer — the device to read from. Required.
  • service UUID / characteristic UUID — the characteristic to read: 16-bit (2a6e) or 128-bit. Required. Apps such as nRF Connect list a device's UUIDs.
  • encoding — how the bytes read become payload: bytes, text, int8 to uint32, or float32, little-endian. Default bytes. It also sets the output's type.

Wiring

Input — any message starts a read. Wire a timer in to read at an interval.

Output — the incoming message, with payload set to the value read.

Behavior

The read waits up to 5 seconds for the device's answer, and the message's chain waits with it. For a device that pushes its values, a ble notify node needs no polling.

Errors

A message that arrives while the peer isn't connected, a read that times out or fails, or a value that doesn't decode (1 byte for a uint16) is reported on the console and the message is dropped.

What a device sends is untrusted input: check it before acting on it.