DMX

DMX is a standard protocol that's commonly used for digital stage lighting. See the Wikipedia article on DMX512

Here we're only going to cover reception of DMX. Head over to the forums if you're interested in transmission.

Wiring

DMX protocol uses the same logic levels as RS-485. You can get DMX shields for Arduino which you can wire up (make sure you buy one that can receive!), but you can also use a normal RS-485 converter chip such as the MAX485. Modules are available for just a few pounds on eBay.

DMX Receive

Simply wire the receive wire from your level converter up to a pin on your Espruino that has a USART_RX peripheral (check the reference page for your board). If you're using a level converter with a 5v output make sure you're connecting to a 5v-capable pin (one that doesn't have 3.3v by it in the pinout diagram). If you were wiring to the Espruino Pico you could use Pin B7 (but watch out for the console swapping to Serial when USB is disconnected).

Software

Using the module is easy. Simply call require("DMX").connectRX with the pin, the maximum amount of data you want, and a function to be called when the data is received.

The following example will light LED1 and LED2 based on DMX channels 1 and 2.

require("DMX").connectRX(pin, 6, function(data) {
  analogWrite(LED1, data[1]/256, {soft:true});
  analogWrite(LED2, data[2]/256, {soft:true});
  // or console.log(data.join(","));
});

Note:

  • Some DMX transmitters don't transmit the full 512 bytes of message
  • Data comes in from DMX quite quickly. If you don't handle each packet quickly enough, the next packet could be corrupted.
  • If you print the received data to the console (the commented out code), it make take so long to print it that the next packet gets corrupted.

Using

No tutorials use this yet.

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