@chirimen/tca9548a

Driver for TCA9548A with WebI2C

Usage

get(channel) returns an object implementing I2CPort, scoped to one downstream channel. Pass it straight into another driver's constructor, just like a plain I2CPort. It selects the channel and serializes access on its own, so you don't need to call write() before every read or write:

import { requestI2CAccess } from "node-web-i2c";
import TCA9548A from "@chirimen/tca9548a";
import SHT30 from "@chirimen/sht30";

const i2cAccess = await requestI2CAccess();

const mux = new TCA9548A(i2cAccess.ports.get(1));

const s0 = new SHT30(mux.get(0));
const s1 = new SHT30(mux.get(1));

await s0.init();
await s1.init();

while (true) {
  console.log(await s0.readData());
  console.log(await s1.readData());
}

read() and write() still work too, for selecting a channel manually before each access.

Every I2C operation issued through a mux instance (whether via read()/write() or a get(channel)-wrapped device) is serialized, so it's safe to call them concurrently. If a single operation doesn't complete within 5 seconds, that call rejects with TCA9548ALockTimeoutError so your code isn't left waiting forever. Later calls on the same mux still wait for the stuck operation to actually finish, though — there's no way to cancel an I2C transaction once it's issued, so letting other calls proceed early could interleave with whatever the stuck operation eventually does to the bus.

Breaking changes in 3.0.0

TCA9548A is now a real class. new TCA9548A(bus) still works exactly as before, but calling it as a plain function (TCA9548A(bus), without new) now throws instead of returning a driver instance.

API

Class: TCA9548A

Defined in packages/tca9548a/index.js:55

Constructor

▸ new TCA9548A(bus: I2CPort, address: TCA9548AAddress): TCA9548A

Defined in packages/tca9548a/index.js:79

Parameters:

| Name | Type | Default | | --------- | ---------------------------------------------------------------- | ------- | | bus | I2CPort | - | | address | TCA9548AAddress | 112 |

Properties and methods

• i2cSlave: null | I2CSlaveDevice = null as I2CSlaveDevice | null

• init(): Promise‹void›

• read(): Promise‹TCA9548AChannel | null›

• write(channel: TCA9548AChannel): Promise‹void› — throws RangeError for a channel outside 0-7.

• get(channel: TCA9548AChannel): I2CPort-like object — see Usage. Calling get() twice with the same channel returns the same object. Throws RangeError for a channel outside 0-7.

Const TCA9548AChannels

• TCA9548AChannels: ReadonlyArray‹TCA9548AChannel› = [ 0, 1, 2, 3, 4, 5, 6, 7 ]

Defined in packages/tca9548a/index.js:23

TCA9548AAddress

Ƭ TCA9548AAddress: 112 | 113 | 114 | 115 | 116 | 117 | 118 | 119

Defined in packages/tca9548a/index.js:4

I2C bus slave address (default 0x70; when A0-A2 pins are high(1)/low(0) 0x70+4*A2+2*A1+A0 )

TCA9548AChannel

Ƭ TCA9548AChannel: 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7

Defined in packages/tca9548a/index.js:9

8 switch channels for I2C data flow

TCA9548ANotFoundError

An Error thrown when the mux chip itself doesn't respond at its configured address.

TCA9548ALockTimeoutError

An Error thrown when a single I2C operation doesn't complete within 5 seconds.

License

MIT