pi_glow
v0.1.0

View Source PiGlow.LED (pi_glow v0.1.0)

A structure representing a single LED on a PiGlow device.

These are the values that the PiGlow.map_* functions pass to the user-supplied function. Your application code can choose which LEDs to operate on by looking at the LED's properties:

  • index — the position of the LED in the binary versions of PiGlow.set_enable and PiGlow.set_power
  • arm — which of the three arms the LED is on (clockwise)
    • 1 — the top arm, directly below the "PiGlow" text
    • 2 — the right arm, on the side with the Pimoroni URL
    • 3 — the left arm, on the side with the small text and icons
  • ring — how far from the centre the LED is, in the range of 1..6
  • colour — the LED colour, as an atom

Note that ring and colour are effectively the same value, just expressed two different ways:

  • ring 1 corresponds to colour :white
  • ring 2 corresponds to colour :blue
  • ring 3 corresponds to colour :green
  • ring 4 corresponds to colour :amber
  • ring 5 corresponds to colour :orange
  • ring 6 corresponds to colour :red

Additionally, this module also contains utility functions relating to LEDs and LED brightness.

Link to this section Summary

Types

colour()
t()

Functions

gamma_correct(value)

Calculates the power value needed to approximate a given brightness.

leds()

Return the list of LEDs on a PiGlow device.

Link to this section Types

Link to this type

colour()

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@type colour() :: :white | :blue | :green | :amber | :orange | :red
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t()

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@type t() :: %PiGlow.LED{arm: 1..3, colour: colour(), index: 1..18, ring: 1..6}

Link to this section Functions

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gamma_correct(value)

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@spec gamma_correct(0..255 | float()) :: 0..255

Calculates the power value needed to approximate a given brightness.

The relationship between how much power is sent to an LED, and how bright that LED actually shines, is a non-linear one — i.e. going from 90% to 95% of max brightness requires a significantly larger increase in energy than going from 5% to 10% of max brightness. This function attempts to correct for that by applying an exponential curve to the supplied brightness value.

The value argument can be either an integer between 0 and 255 inclusive, or a float between 0.0 and 1.0 inclusive. The result will follow this pattern:

  • gamma_correct(v) = 0 when v is 0 or 0.0
  • gamma_correct(v) = 255 when v is 255 or 1.0
  • otherwise, gamma_correct(v) will follow an exponential curve from 1 to 255

Returns an integer in the range of 0..255, which can be passed to the power-based functions in PiGlow.

examples

 Examples 

# Pulse all lights once:
iex> [0..255, 255..0] |>
...>   Enum.flat_map(&Enum.to_list/1) |>
...>   Enum.map(&PiGlow.LED.gamma_correct/1) |>
...>   Enum.each(fn value ->
...>     PiGlow.map_power(fn _ -> value end)
...>   end)
:ok
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leds()

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@spec leds() :: [t()]

Return the list of LEDs on a PiGlow device.

examples

 Examples 

# Find all green LEDs:
iex> PiGlow.LED.leds() |> Enum.filter(fn led -> led.colour == :green end)
[
  %PiGlow.LED{index: 6, arm: 1, ring: 3, colour: :green},
  %PiGlow.LED{index: 14, arm: 2, ring: 3, colour: :green},
  %PiGlow.LED{index: 4, arm: 3, ring: 3, colour: :green}
]