Go module for controlling the PiDP-11, ie activating leds and getting switch events.

Documentation

Used by blink11.

Light effects

A number of effects are supported:

• Simple (one-shot): optional ramping up or down of brightness when switching a led on or off.
• Flash (periodic): the light stays on and off for the same duration. Supports ramping up/down.
• Strobe (periodic): the light stays on for always the same short duration, and off for a varying duration. Supports ramping up/down.
• Error (periodic): creates a hopefully recognisable brightness envelope.

Brightness envelopes

New effects can easily be added by making new implementations of the Effect interface.

Effects are implemented using an envelope (as in audio synthesis) which defines brightness changes and is either one-shot (eg simply switching a led on or off) or periodic (flashing etc).

An envelope is a sequence of stages. A stage defines a linear progression between two brightness levels, over a certain duration.

Brightness transitions

When switching a led on or off, the current brightness of the led is taken into account. For example if the led brightness is at 50% and we switch it off with a ramping down duration of 1 second, the led will be off after half a second.

Similarly, when changing the effect for a led (eg changing from flashing to strobing, changing the flashing frequency, changing the ramping up/down durations or any combinations of those), we transition smoothly to avoid jarring visual artifacts.

Events

When a switch is actioned, an event is emitted on buffered channel Events(). The events should be read reasonably quickly to avoid blocking the main loop.

Demo program

See cmd/demo/main.go.

Depending on your rpi architecture, build with:

• GOOS=linux GOARCH=arm GOARM=7 go build ./cmd/demo/
• GOOS=linux GOARCH=arm64 go build ./cmd/demo/