smbus_demo Directory Reference

Directory dependency graph for smbus_demo:

Directories
	src

Detailed Description

Standalone demo and gate for the SMBus 3.2 protocol layer (ra8_smbus, #128), which frames Send Byte / Receive Byte / Read Byte Data / Block transactions on top of the IIC_B (I3C-in-I2C-mode) controller and delegates raw byte movement to ra8_i3c. It previously had no example and no gate.

The target is the ST LSM6DSO IMU at 7-bit address 0x6B on the Pmod1 I2C side – a plain register-indexed I2C device, so it answers the SMBus byte protocols natively, SMBus being electrically I2C. The app reads the fixed WHO_AM_I register two ways, exercising three protocol shapes:

SMBus protocol (3.2 spec)	Wire frame (PEC off)
Read Byte Data (6.5.5)	S addr_w [0x0F] Sr addr_r [0x6C] P
Send Byte (6.5.2)	S addr_w [0x0F] P (sets reg pointer)
Receive Byte (6.5.3)	S addr_r [0x6C] P

Both reads must return 0x6C. PEC is disabled because the IMU is not an SMBus PEC device; a production SMBus target such as a smart battery or power IC would use it, which cfg.pec_enabled turns on. A NAK or a wrong value halts on a BKPT before the PASS line, so the gate cannot pass by accident. The PEC CRC-8 helper is covered on the host by tests/misc/src/test_ra8_smbus.c.

Using the IMU as the target is a convenience: any register-file I2C device demonstrates the protocol-layer framing end to end.

Blocked on

The IMU 12 Click has to be fitted to the Pmod1 I2C side (P511/SDA1 + P512/SCL1) – the same prerequisite as imu_lsm6dso_demo, and the EK-RA8D2 has no native MikroBUS socket. Without the part the bring-up NAKs. The device is modelled on the IIC_B bus off-target, so the transactions return through the genuine ra8_smbus -> ra8_i3c path with no stub.