I2C

I2C is a source-board peripheral surface. It is useful for sensors and small external devices, but it is not part of the beginner Froth Machine workshop path.

Availability

The esp32-devkit-v1 board source exposes I2C bindings. The Froth Machine public workshop board does not currently teach I2C as a front-door feature.

Handles are small integers returned by setup words and passed back into later calls. Native ESP-IDF pointers do not become Froth values.

Bus And Device

i2c.init: (sda, scl, freq) -> Int

Creates a bus handle.

i2c.bus is i2c.init: SDA, SCL, 400000

i2c.add-device: (bus, addr, speed) -> Int

Adds one 7-bit-addressed device and returns a device handle.

i2c.dev is i2c.add-device: i2c.bus, 104, 400000

i2c.rm-device: (device) -> nil

Releases a device handle.

i2c.del-bus: (bus) -> nil

Releases a bus handle.

Probe And Byte I/O

i2c.probe: (bus, addr) -> Bool

Checks whether one address responds.

i2c.probe: i2c.bus, 104

i2c.write-byte: (device, byte) -> nil

Writes one byte.

i2c.read-byte: (device) -> Int

Reads one byte.

Register I/O

i2c.write-reg: (byte, device, reg) -> nil

Writes one byte to a register.

i2c.write-reg: 0, i2c.dev, 107

i2c.read-reg: (device, reg) -> Int

Reads one byte from a register.

i2c.read-reg: i2c.dev, 117

i2c.read-reg16: (device, reg) -> Int

Reads a 16-bit register value.

Notes

Keep setup in one named place:

i2c.bus is nil
i2c.dev is nil

to sensor.setup [
  set i2c.bus to i2c.init: SDA, SCL, 400000;
  set i2c.dev to i2c.add-device: i2c.bus, 104, 400000
]

Do not save native assumptions. The saved overlay may remember the small integer handles, but hardware should be initialized from boot after restore.