ds2408

DS2408 1-Wire 8-channel I/O chip driver for Node.js, using the Linux kernel's w1-gpio / w1-therm sysfs interface.

• Zero runtime dependencies
• ESM, TypeScript types
• Node 22+

Requirements

• Linux host with the 1-Wire kernel modules loaded (w1-gpio, wire).
• DS2408 attached on the 1-Wire bus, exposed under /sys/bus/w1/devices/29-*.
• Process needs read/write access to those sysfs files (usually root, or a udev rule).

Install

npm install ds2408

Usage

import { DS2408, findAttachedDevices } from 'ds2408';

// Auto-select the first attached DS2408.
const ds = await DS2408.open();

// Or pass an explicit serial.
// const ds = await DS2408.open('29-0000017d3b86');

// Read live pin levels.
console.log('state:', (await ds.readState()).toString(2).padStart(8, '0'));

// Drive specific bits low (sink), float others (release to external pull-up).
await ds.sinkOutputs(0b0000_0011);  // channels 0 and 1 sink
await ds.floatOutputs(0b1111_1100); // channels 2..7 float

// Read the current output latch.
console.log('output:', await ds.readOutput());

// React to edges on input pins.
const off = ds.onActivity((activity, state) => {
  console.log(`activity=${activity.toString(2)} state=${state.toString(2)}`);
});
ds.startActivityLoop({ loopDelay: 50 });

// Later …
await ds.stopActivityLoop();
off(); // detach the listener

API

DS2408.open(serial?, options?)

Async factory. Reads the current output-latch register before returning so the instance is consistent.

| option | type | default | description | | ------------------- | ------ | ----------------------------- | ---------------------------------------------------------- | | verificationLoops | number | 2 | Consecutive identical reads needed before returning a value. Filters transient mid-update values. | | devicesDir | string | /sys/bus/w1/devices | Sysfs root. Override for tests. |

findAttachedDevices(devicesDir?)

Returns the serial numbers of all DS2408 chips currently on the bus.

Reading

• readState() — live PIO pin levels (1 = high, 0 = low).
• readOutput() — current output-latch register (and updates the internal cache).
• readControl() — status_control byte.
• readCondSearchMask() / readCondSearchPolarity() — conditional-search registers.
• pollActivity() — read & write-clear the activity byte; returns { activity, state }.

Writing

• setOutput(byte) — write the entire output-latch byte (0..255). Bits set to 0 sink the pin; bits set to 1 float it.
• sinkOutputs(mask) / floatOutputs(mask) / maskedSetOutputs(mask, value) — manipulate outputs relative to the cached state.
• setControl(byte) / setControls({ PLS, CT, ROS, PORL }, read = true) — write the status-control byte. setControls modifies only the bits you specify (when read = true).

Activity loop

• startActivityLoop({ loopDelay = 100 }) — start polling the activity register on a timer; non-zero readings notify all onActivity listeners.
• stopActivityLoop() — stop the loop; resolves once the in-flight tick (if any) finishes.
• onActivity(listener) — register a listener; returns a removal function.
• isActivityLoopRunning — true while the loop is active.

License

MIT — see LICENSE.