iic_b_facade_demo Directory Reference

Directory dependency graph for iic_b_facade_demo:

Directories
	src

Detailed Description

Exercises IIC_B – the RA8D2 I3C block in legacy I2C-compatibility mode, twin of the RIIC path – through the ra8_io_i2c_bus facade in BOTH roles the peripheral supports, controller and peripheral (target), on the one channel.

As controller it runs the textbook "point at a register, then read it" pattern: write the 2-byte pointer 0x8140, repeated START, read 4 bytes. The target is the on-board GoodIX GT911 touch controller at 7-bit 0x5D, and 0x8140 is its PRODUCT_ID – the same probe ra8_touch performs at bring-up, so a real device answers on a stock EK-RA8D2. As peripheral it reprograms the same channel as an addressed target at own-address 0x42, draining each byte a bus controller writes (NTST.RDBFF0) and echoing it back on the following controller-read (NTST.TDBEF0).

The facade point

The controller half never names ra8_i3c_* at the call site. A board revision that moved this bus onto a RIIC channel would change the single bind call and nothing else; every transfer stays byte-identical. That Liskov-substitutable "twin I2C backends" property is the reason the facade exists.

The target half degrades honestly

The target role needs an EXTERNAL I2C controller on the bus – a Pi running i2cset / i2cget against 0x42 is enough. The stock bench rig provides none, so the peripheral round-trip count stays at zero there, and it is reported but never gated: the same honest degradation i2c_peripheral_responder and i3c_i2c_peripheral_demo use. Under the emulator both halves do run, since it models the GT911 on the controller bus AND plays the external controller driving the firmware's target role.

Part of the #252 example-coverage sweep; closes #255.