sainsmart-16-hid

Control the Sainsmart 16 relay USB HID device from node.js.

Alpha

I'll be using this module to create an irrigation controller. Until I'm satisfied with its meatspace operation, this should be considered alpha software!

Usage

$ npm install sainsmart-16-hid

const Relay = require('sainsmart-16-hid');

let relay = new Relay();

// enable relays 0 and 4
relay.write(0b0000000000010001);
// enable relays 14 and 15
relay.write(Math.pow(2, 14) | Math.pow(2, 15));
// leave 14 & 15 enabled, but enable relay 5
relay.set(5, true);
// check to see if relay 14 was enabled
(Math.pow(2, 14) & ~relay.state) === 0;
// or
relay.stateArray[14] === true;
// turn off relay 14
relay.set(14, false);

Keep in mind that constructing a Relay object will send a reset command to the module and set all relays to zero. This is so that your control module can begin in a known state in the event of a crash or restart. If you need to access the state of the usb device when set by another piece of software, consider another library.

API

new Relay([path])

Path is optional, and can be used to specify a specific device for node-hid. If not specified, the first Sainsmart 16-relay USB HID device found will be used.

relay.state

16-bit integer representation of the state of the relays. 0b0000000000000001 means relay 0 is enabled, 0b1000000000000000 means relay 15 is enabled, etc.

relay.stateArray

Another representation of the relay states, an array of booleans.

relay.stateArray // relays 0, 4, and 15 are enabled
> [true, false, false, false, true, false, false, false, true, false, false, false, false, false, false, true];

relay.read(callback)

Sends a read command to the USB device. callback(err, data) (required) will include any error and data will be the 16-bit integer representation of the state of the relays. relay.state and relay.stateArray will be updated when this function completes. Note that you shouldn't need this function. Each time write or set is called this information can be accessed from relay.state or relay.stateArray.

relay.write(state)

Used to change the state of all the relays on the device. For example:

// turn on relays 0, 3, and 14. everything else off.
relay.write(0b0100000000001001);
// turn everything off except relays 5 & 6
relay.write(Math.pow(2, 5) | Math.pow(2, 6));

relay.set(relay, state)

Turn a specific relay on or off, without affecting the state of other relays.

relay.write(Math.pow(2, 1) | Math.pow(2, 15));
relay.set(15, false);
relay.set(14, true);
relay.stateArray
> [false, true, false, false, false, false, false, false, false, false, false, false, false, true, false]

Credit

All credit goes to mvines/relay for documenting the protocol for communicating with this device. I just made an API that fits my needs.