Big brother to the Blinkt, small brother to the Unicorn HAT, the PHAT version is a 4 x 8 matrix of RGB LEDs.

At £10 it gives you twice as many LEDs per pound as the Blinkt (a 1 x 8 strip of the same LEDs costing £5). But what am I going to do with the extra ranks of multi-coloured shiny sparkles? To be honest, I've no idea really.

The Blinkt is a very neat little strip of LEDs that can do a nice job of providing some very pretty status monitoring lights. The Unicorn pHAT could act as an expanded version of the same thing, but I can pretty much eyeball a strip of 8 lights and get an instant idea of what's going on. I can't do the same when there are 4 strips packed together - it's just too many twinkling coloured lights.

To use this as a status panel, I'll be needing a lookup table to remind me what the rows/cols or individual lights represent. Yes the status lights could be grouped (e.g. top row = web server, 2nd row = network, 3rd row = OS, 4th row hardware/environment) but still that's a lot of lights to remember.

Conceptually there are really 4 dimensions available on this panel to use for data display:

  1. 4 rows
  2. 8 columns
  3. 255 x 255 x 255 for colours
  4. 0.0 -> 1.0 in 0.05 steps for brightness

The problem is that the dimensions with the highest theoretical resolution can't really be used at those resolutions. Probably I can distinguish about 20 different colours as far as assigning meaning to them goes. Probably the brightness is even worse, maybe there are 5 recognisable brightness steps.

When it comes to making the most use of the range of brightness and colours we're better off using them for a continuous variable we're interested in from a "trending" viewpoint. For example, time series representation - that light is changing colour over time, or getting brighter. Rather than discrete enumerated status values (red = bad, green = good, orange = unhappy, ...).

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