{"id":1722,"date":"2021-02-16T08:31:08","date_gmt":"2021-02-16T08:31:08","guid":{"rendered":"https:\/\/ofalcao.pt\/blog\/?p=1722"},"modified":"2021-02-18T07:48:04","modified_gmt":"2021-02-18T07:48:04","slug":"lego-and-dmx","status":"publish","type":"post","link":"https:\/\/ofalcao.pt\/blog\/2021\/lego-and-dmx","title":{"rendered":"LEGO and DMX"},"content":{"rendered":"
This post is part 1 of 6 of \u00a0LEGO and DMX<\/a><\/div>\n

Playing with MIDI, reading a lot, browsing through musical equipments… and DMX<\/a> cames out.<\/p>\n\n\n\n

DMX is like a custom RS-485<\/a> network. A master device sends data at 250 kHz to slave devices, each of them listening to a different “channel” or address. Typical DMX devices (“fixtures”) are stage lights but you can find fog machines, laser projectors, bubble machines, relay boards, analog interfaces…<\/p>\n\n\n\n

On a studio scenario you can even join MIDI with DMX so you can create a performance combining music and lights or other kind of effects.<\/p>\n\n\n\n

Generating a 250 kHz stream of data isn’t difficult, there are FTDI devices that can do that. I could use the same kind of setup I use to generate LEGO Power Functions IR signals<\/a> to generate DMX signals.<\/p>\n\n\n\n

In fact, people are already doing it. There are a few tutorials on how to create a DMX controller for less than $10 but I prefer this one<\/a> (it costed me a bit more than 10\u20ac but it was really straightforward, just a FTDI485 cable and a XLR 3-pin female connector.<\/p>\n\n\n\n

It can be used with QLC+<\/a> (an open source DMX controller software) but that’s overkill for a MINDSTORMS EV3 so after a short search I found a python library to use it directly (dmx485<\/a>).<\/p>\n\n\n\n

So you connect your DYI DMX adapter to your EV3:<\/p>\n\n\n\n

[1218334.312176] usb 1-1.2: New USB device found, idVendor=0403, idProduct=6001
[1218334.312248] usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[1218334.312287] usb 1-1.2: Product: USB-RS485 Cable
[1218334.312322] usb 1-1.2: Manufacturer: FTDI
[1218334.312355] usb 1-1.2: SerialNumber: FT4NMHF6
[1218334.800717] usbcore: registered new interface driver usbserial
[1218334.936770] usbcore: registered new interface driver ftdi_sio
[1218334.937337] usbserial: USB Serial support registered for FTDI USB Serial Device
[1218334.938673] ftdi_sio 1-1.2:1.0: FTDI USB Serial Device converter detected
[1218334.939512] usb 1-1.2: Detected FT232RL
[1218334.956748] usb 1-1.2: FTDI USB Serial Device converter now attached to ttyUSB0<\/pre>\n\n\n\n
Here it is assigned  to  ‘\/dev\/ttyUSB0’<\/p>\n\n\n\n
Now we just need to install ‘dmx485’:<\/p>\n\n\n\n
pip3 install dmx485<\/pre>\n\n\n\n
 (if you have a fresh ‘ev3dev’ installation you probably need to install ‘pip3’ first) <\/p>\n\n\n\n
For testing, the script on ‘dmx485’ homepage is enough but I adapted it for my first python DMX script to control my cheap DMX RGB PAR spotlight (after reading the manual to find how it works – it uses 4 DMX channels for Master, Red, Green and Blue values)<\/p>\n\n\n\n
!\/usr\/bin\/env python3\nimport time\nimport dmx\nimport random\n\nrandom.seed()\n\nCMD = [0]*512\nCMD[3] = 255  # Master Dimmer\nCMD[4] = 0    # Red Dimmer\nCMD[5] = 0    # Green Dimmer\nCMD[6] = 0    # Blue Dimmer\n\nBLANK = [0]*512\n\nDELAY = 0.2\nsender = dmx.DMX_Serial('\/dev\/ttyUSB0')\nsender.start()\n\n# WHITE\nCMD[4] = 255\nCMD[5] = 255\nCMD[6] = 255\nsender.set_data(bytes(CMD))\ntime.sleep(2)\nsender.set_data(bytes(BLANK))\n\n# RED dimmer\nCMD[4] = 0\nCMD[5] = 0\nCMD[6] = 0\nfor i in range(0, 256, 8):\n    CMD[4] = i\n    sender.set_data(bytes(CMD))\n    time.sleep(DELAY)\nsender.set_data(bytes(BLANK))\n\n# GREEN dimmer\nCMD[4] = 0\nfor i in range(0, 256, 8):\n    CMD[5] = i\n    sender.set_data(bytes(CMD))\n    time.sleep(DELAY)\nsender.set_data(bytes(BLANK))\n\n# BLUE dimmer\nCMD[5] = 0\nfor i in range(0, 256, 8):\n    CMD[6] = i\n    sender.set_data(bytes(CMD))\n    time.sleep(DELAY)\nsender.set_data(bytes(BLANK))\n\n# MASTER dimmer\nCMD[4] = 255\nCMD[5] = 255\nCMD[6] = 255\nfor i in range(0, 256, 8):\n    CMD[3] = i\n    sender.set_data(bytes(CMD))\n    time.sleep(DELAY)\nsender.set_data(bytes(BLANK))\n\n# RGB random\nCMD[3] = 255\nCMD[4] = 0\nCMD[5] = 0\nCMD[6] = 0\nfor step in range(50):\n    CMD[4] = random.randint(0,255)\n    CMD[5] = random.randint(0,255)\n    CMD[6] = random.randint(0,255)\n    print(CMD[4], CMD[5], CMD[6])\n    sender.set_data(bytes(CMD))\n    time.sleep(DELAY)\nsender.set_data(bytes(BLANK))<\/pre>\n\n\n\n
\n