Dmx interface for raspberry pi

Introduction

The DMX interface for raspberry pi allows you to interface a raspberry pi with DMX hardware.

There is also a version "with FT245" That version adds the option to use your raspberry pi with our board as an Enttec USB Pro compatible device from another computer (raspberry pi or PC, Windows or Linux)

software

There are several software packages that can be used with your DMX interface for Raspberry pi.

First there are QLC+ and OLA. These are packages that run on Linux on the raspberry pi and allow you to control a DMX Universe.

Second, there are several packages by Arjan van Vught that use the raspberry pi "bare metal".

QLC+ and OLA

Don't forget to remove the console and getty from the serial port that the DMX inteface is using.

See: http://elinux.org/RPi_Serial_Connection#Preventing_Linux_using_the_serial_port

QLC+

Harold van Hulten wrote a nice "howto". See: http://www.udenix.nl/2016/how_did_i/rpi2dmx/

QLC+ 's home is at: http://www.qlcplus.org

OLA

Jessie

On raspbian jessie installing OLA is easy: apt-get install ola should do the trick. The downside is however that it doesn't work :-( .

what does work however is:

mkdir ola
cd ola
wget https://github.com/OpenLightingProject/ola/archive/0.10.1.tar.gz
tar xvfz 0.10.1.tar.gz
cd ola-0.10.1
autoreconf -i
./configure 
make -j 5
sudo make install

wheezy

On Wheezy, adding

deb   http://apt.openlighting.org/raspbian  wheezy main

to /etc/apt/sources.list, and then the apt-get install ola should work.

There are some important hints at: http://opendmx.net/index.php/OLA_Device_Specific_Configuration#UART_native_DMX

raspberry pi 3

Add:

dtoverlay=pi3-disable-bt

Otherwise, the wrong UART will be used. The "wrong" uart will

• change baudrate unexpectedly when the CPU feels hot.
• I haven't figured out if it CAN do the required baud rate, and/or how to do that.

This has the consequence that we've stolen back the good UART from the bluetooth that's present on the PI3.

On the raspberry pi forums there is talk about re-enabling bluetooth at a lower performance level.

all raspberries

Most importantly: add:

init_uart_clock=16000000

to your config.txt file in the /boot directory.

Next, you need to configure ola to use the native-uart plugin. This is described at: http://www.raspberrypi-dmx.com/raspberry-pi-ola-dmx512-sender

Locate your ola-uartdmx.conf (on some systems I'm told it is in /etc/ola/conf/, on others /var/lib/ola/conf/, and in some cases: /root/.ola/ola-uartdmx.conf or /home/pi/.ola/ola-uartdmx.conf. One of the ways to find out is to look at the -c argument on your running olad.). Edit it and set enabled to true, set the correct device (ttyS0 on rpi3, ttyAMA0 on others), and add /dev/ttyAMA0-break = 100 and /dev/ttyAMA0-malf = 100 . It should then look like:

/dev/ttyAMA0-break = 100
/dev/ttyAMA0-malf = 100
device = /dev/ttyAMA0
enabled = true

Then set the board to output mode. I would recommend creating a small script (sudo nano /usr/bin/set_dmx_mode; sudo chmod 755 /usr/bin/set_dmx_mode) :

#!/bin/sh
# set_dmx_mode
if [ $# -lt 1 ] ; then 
  echo 'on or off?'
  exit 1
fi

if [ ! -d /sys/class/gpio/gpio18 ] ; then 
   echo 18 > /sys/class/gpio/export
fi
echo out > /sys/class/gpio/gpio18/direction
echo $1 > /sys/class/gpio/gpio18/value

then calling the script:

sudo set_dmx_mode 1

I recommend putting that line in /etc/rc.local so that it gets executed at boot time so you don't have to worry about it. (IIRC there is an "exit 0" in there, so don't put it AFTER that!)

Note that the earlier versions of the DMX board have a bug that when the GPIO pin is an input (not driven) it will configure the board as an output. This is not desirable. Newer versions (starting 1.4) will have this "fixed" and the "default" will be "DMX IN" mode.

This does mean that you can get away with forgetting about this gpio18 business if you have an older version. (I just realized I was getting away with this.... :-) )