I²C MessagePort based Bus

Provides tooling that allows for I2CBus to be hosted natively, over MessagePort, within Worker and over WebSockets.

This allows the I2CBus api to be used in a wide range of deployment cases.

It can also be using with bus Multiplexing such as @johntalton/i2c-bus-tca9548a that adheres to the I2CBus interface. As well as using i2c-bus as the default concrete/base implementation.

Provided Abstraction

Key is providing multiple abstraction layers.

• A Message type definition (including Read, ReadResult, Error, etc)
• An I2CPort function that maps Message into I2CBus commands on provided bus
• And I2CPortBus which implements I2CBus over a MessagePort interface

The corresponding WebSocket to MessagePort example can be run to provide this service.

Message

The Message definition layer provides a naming convention and contract without implementation details. It is ideal for abstracting the service at each layer.

I2CPort

The port utility provides a handleMessage function. By which, given a provided I2CBus and Message, will execute that bus command.

const busX = ... // a I2CBus impl from somewhere
const result = await I2CPort.handleMessage(busX, {
  namespace: 'NS',
  type: 'readI2cBlock',
  address: 0x00,
  cmd: 0x00,
  length: 3
})

console.log(result)
/*
{
    namespace: 'NS',
    address: 0,
    type: 'readResult',
    bytesRead: 3,
    buffer: Uint8Array(3) [ 1, 3, 4 ]
    ...
}
*/

This message to bus method and back is particularly useful when abstracting the I2CBus class methods accros a MessagePort implementation such as I2CPortBbus.

I2CPortBus

The implementation of I2CBus allows for creating a instance classes which use the generic I2CBus interface and alow them to run atop of a MessagePort.

Useful application (as seen in the examples) of this are: - Workers: allow for running I2CBus implementation and Sensor across worker (shared i2c service for multiple workers) - WebSockets: allow for transmission of Message across a WebSocket to allow for remote i2c Sensor implementations.

ArrayBuffer and friends

The current implementation attempts to preserve a common ArrayBuffer interface across the implementation in order to provide flexibility