# scenic_driver_nerves_rpi
The main driver for rendering Scenic scenes on a Raspberry Pi device.
So far only tested on Raspberry Pi 3 devices. In other words, it is still early days for this driver. There will probably be changes in the future. Especially regarding multi-touch.
Installation
In your Nerves applications dependencies include the following line
...
{:scenic_driver_nerves_rpi, , "~> 0.10"}
...
Configuration
Configure the rpi driver the same way you configure other drivers. Add it to the driver list in your ViewPort's config.exs file.
config :sample, :viewport, %{
size: {800, 480},
default_scene: {Sample.Scene.Simple, nil},
drivers: [
%{
module: Scenic.Driver.Nerves.Rpi,
}
]
}
Tips
As I've used Scenic on a Raspberry Pi device, sometimes I want to make the whole Scene bigger in order to make it more readable. You can apply transforms to the entire ViewPort to achieve this. This looks the same as any list of styles or transforms that you would apply to any part of a graph.
You can even rotate the entire scene if you want to change the orientation of the screen.
config :sample, :viewport, %{
size: {800, 480},
opts: [scale: 1.2], # <----- Apply transforms & styles here
default_scene: {Sample.Scene.Simple, nil},
drivers: [
%{
module: Scenic.Driver.Nerves.Rpi,
}
]
}
Performance
Performance on a Raspberry Pi is OK. Not Great. The VC4 chip is slower than I would like with 2D style drawing and there is an ongoing investigation to improve rendering performance.
The good news is that Scenic only renders when there is a change. So if you aren't pushing graphs, then it isn't spending energy drawing the screen.