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68 lines
2.4 KiB
Markdown
68 lines
2.4 KiB
Markdown
# node-enttec-open-dmx-usb 🔌
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> A Node.js library for interacting with the
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> [Enttec Open DMX USB interface](https://www.enttec.co.uk/en/product/controls/dmx-usb-interfaces/open-dmx-usb/)
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As it uses `serialport` under the hood, it should also work in
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[these environments](https://serialport.io/docs/guide-platform-support#supported-platforms-and-architectures).
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## Install
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The minimum required Node.js version is `v18.0.0`.
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```sh
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yarn add enttec-open-dmx-usb
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# or
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npm install enttec-open-dmx-usb
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```
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## Usage
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[**View documentation on jsdocs.io**](https://www.jsdocs.io/package/enttec-open-dmx-usb#EnttecOpenDMXUSBDevice)
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```js
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import { EnttecOpenDMXUSBDevice as DMXDevice } from "enttec-open-dmx-usb"
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(async () => {
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const device = new DMXDevice(await DMXDevice.getFirstAvailableDevice())
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device.setChannels({
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1: 0xFF,
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2: 0x44
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})
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// same as
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device.setChannels([0xFF, 0x44])
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// same as
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device.setChannels(Buffer.from([0xFF, 0x44]))
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})()
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```
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### What to do when this doesn’t work
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TLDR: Because `setTimeout` is imprecise, install [`easy-sleep`](https://github.com/qufei1993/easy-sleep) and
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pass the `usleep` function provided by it as the third parameter to the constructor of `EnttecOpenDMXUSBDevice`.
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See the example below.
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From [the Node.js documentation](https://nodejs.org/api/timers.html#settimeoutcallback-delay-args) regarding `setTimeout`:
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> Node.js makes no guarantees about the exact timing of when callbacks will fire, nor of their ordering.
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> The callback will be called as close as possible to the time specified.
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Because of this and the passive nature of the Enttec Open DMX USB interface, sometimes the timing requirements of the DMX specification are not met.
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Using a library such as [`easy-sleep`](https://github.com/qufei1993/easy-sleep) which allows sleeping (i. e. blocking the event loop) for a precise
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amount of microseconds is a possible workaround.
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You may pass a function sleeping for `n` *micro*seconds as the third parameter to the constructor of `EnttecOpenDMXUSBDevice`.
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For example, using `easy-sleep`:
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```js
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import { EnttecOpenDMXUSBDevice as DMXDevice } from "enttec-open-dmx-usb"
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import easySleep from "easy-sleep"
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new DMXDevice(await DMXDevice.getFirstAvailableDevice(), true, easySleep.Thread.usleep)
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```
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## Events
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`ready` - `startSending` may be called.
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`error` - An error occurred. `error` events from `serialport` are passed through.
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