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OLA is a software framework for interfacing with various DMX protocols - see openlighting.org/ola. The website/wiki seems to be a bit out of date, but the github repository is still getting (occasional?) updates.

The tutorial for getting started on a Raspberry Pi suggests using their pre-built Raspbian images, but they are (at least) 5 years old - plus I want to install it on an existing Raspberry Pi. The general Linux Install guide seems to imply that you’re likely to have to build OLA from the source code - there’s a link to some notes on installing a pre-packaged version for Debian / Ubuntu, but the repositories for Raspbian seem to be 4 or 5 years old.

However, after all of that, it seems that OLA is available via the standard raspbian repository (v.0.10.7 as of Jan 2020)!.. So installation is easy:

~ $ sudo apt update
~ $ sudo apt install ola

(takes about a minute!)
This installs the software, creates a user called olad (added to the dialout and plugdev groups), and sets up (and starts) OLAd as an init.d service.

So, the current status of OLAd can be checked with:

~ $ service olad status

The init.d script (/etc/init.d/olad) runs the daemon as the user olad, and with /etc/ola as the config dir.

By default, the Paspberry Pi has its SPI interface disabled, so enable it in Menu -> Preferences -> Raspberry Pi Configuration -> Interfaces (reboot not necessary?). Also, the olad user doesn’t have access to the SPI interface, so give permission with:

~ $ grep spi: /etc/group
spi:x:999:pi
~ $ sudo adduser olad spi
Adding user `olad' to group `spi' ...
Adding user olad to group spi
Done.
~ $ grep spi: /etc/group
spi:x:999:pi,olad

Then restart the daemon:

~ $ sudo service olad restart

To make life easier, give yourself permission to edit the config files (they are all owned by olad):

~ $ sudo adduser pi olad

(you’ll probably need to log out and back in again for this to take effect)

The StageProfi plugin seems to try to lock /dev/ttyUSB0 every 5 seconds, which generates a lot of log entries - disable the plugin by editing /etc/ola/ola-stageprofi.conf - change the second line to enabled = false then restart olad:

~ $ sudo service olad restart

At this point you should be able to access the OLA Admin page at (something like) http://192.168.1.75:9090/

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