From Robin Newman via rbnrpi
Recently I purchased a pi-topPULSE module to add to my existing pi-topCEED. You can see the white module plugged into my pi-topCEED in the photo above. I purchased this principally to gain a very convenient built in amplifier and speaker to use with Sonic Pi, without the need for any external cables speakers, amplifiers etc. The volume output is more than adequate for one or two people to listen, although it is only mono and not stereo. If you follow the install procedure at https://github.com/pi-top/pi-topPULSE it switches the audio output automatically to use the built in speaker, when Sonic Pi is launched.
However the pi-topPULSE is much more than just a speaker. IT also contains a microphone, and a grid of 49 LEDs arranged in 7 rows of 7 LEDs. These are RGB LEDs which can be set to any colour and brightness, and which are controlled with the help of a python script.
I had recently manually updated my Raspbian Jessie distribution to the forthcoming Raspbian Stretch, and also installed Sonic Pi 3 onto that, and I thought that it wouod be an ideal opportunity to see If I could control the PULSE LEDs from Sonic Pi, utilising some of the new IO (Input/Output) features which are added with this new release. In particular it can send and receive OSC (Open Sound Control) messages. This is a format which is used to communicate information between widely disparate devices, not necessarily musical, although it can be used with many such. Fortunately python supports OSC messaging if you load an appropriate library, and I decided to use the python-osc library.
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