i2c device

Talks to an I2C device that has no node of its own. Each message that arrives does one transfer.

Properties

I2C bus — the bus the device is wired to. Required. See I2C bus.
operation — read bytes, write msg.payload or scan the bus (read, write, scan in the flow file). Default read.
address — the device's 7-bit address, such as 0x29 or 41. Up to 0x7f. Required except for scan.
register — the register to read or write, such as 0x80. Up to 0xff. Leave it empty for a device without registers.
length (bytes) — for read, how many bytes, 1 to 256. Default 1.

Input — any message starts a transfer. For write, payload is what to send: bytes, a list of numbers 0 to 255, or one number 0 to 255.

Output — the same message, with other fields kept:

read: payload is the bytes read. Reading register 0x92 at address 0x29 (a TCS34725's ID) gives b'D'.
write: payload is unchanged.
scan: payload is the list of addresses that answer, as numbers.

The status dot shows whether the device answers. A transfer that fails sends nothing, and the next message tries again.

Nothing answers at the address. The dot shows disconnected, no reply at 0x29 on I2C bus 0, and the message is dropped. For scan, I2C bus 0 not responding.
A payload that can't be written, such as a bool or a number over 255. The dot shows error with the reason, and the message is dropped.
No address, for read or write. The first message fails with a [NODE_ERROR]: i2c: set the device address (7-bit, e.g. 0x29).
No bus, a bus without pins, or an address or register out of range. Deploy stops and says which.