modelPartialI2cDevice

Information

Base class of the I2C slave peripherals. It cannot be instantiated directly: a concrete peripheral extends it and sets its parameters — see Peripherals.I2cEchoDevice, Peripherals.I2cGroveLcdRgb, or Peripherals.I2cGenericDevice to start from a script template.

Electrical. The peripheral is connected to a real open-drain SDA/SCL bus: it can only pull SDA to ground or release it. Several peripherals and the microcontroller share the same two wires; the "wired AND" of the bus simply follows from Kirchhoff's laws. The lines only go back up thanks to the pull-up resistors: the bus needs at least one pair, carried by a component with usePullUp = true. Without them, the lines stay low and the microcontroller raises OSError(ETIMEDOUT), as on a real circuit.

Behaviour: a Python script only, at the transaction level — the script sees neither the bits, nor the START/STOP conditions, nor the acknowledges:

• on_write(addr, data, t, v): a write phase addressed to it has just ended (STOP or repeated START); data holds all the received bytes.
• on_read(addr, t, v): the master starts reading; return the bytes to send to it (bytes, str, list of integers or integer). They go out one by one; if the master asks for more, on_read() is called again.
• outputs(): read again after each handler, feeds valueOut.
• lines(): optional, read again after each handler, feeds line1/line2 (displays).

The component automatically acknowledges any address of the addresses list and any written byte. It does not answer the other addresses: this is what lets several peripherals share the same bus.

The two dots of the icon light up when the peripheral pulls SDA (amber) and during a phase addressed to it (cyan) — visible while replaying a result with animation in OMEdit. Each completed phase produces a line in the simulation log, prefixed with the component name.

Parameters

Connectors

Components