Micro Dot pHAT review

By Russell Barnes. Posted

A versatile mini LED display with retro appeal

The LTP-305 LED matrices used with the Micro Dot pHAT boast a substantial heritage, having been introduced in 1971 by Texas Instruments. Now manufactured by Lite-On, they come in green and red varieties and feature 5×7 pixels plus a decimal point. Up to six can be mounted on the Micro Dot pHAT, included in the full kit (£22) or purchased separately for £5 per pair (the bare pHAT is just £8), so you could opt for fewer to suit your project’s needs.

The full article can be found in The MagPi 50 and was written by Phil King.

You’ll need to warm that soldering iron up, as the full set requires connecting 118 pins: 13 each for the matrices, plus a standard 40-pin female header. Since each matrix has a leg missing on one side, mirrored on the board, there’s no chance of accidentally inverting them. You’ll want to ensure they’re sitting flush, though.

With the soldering done, it’s simply a matter of installing the software with a single terminal command. This loads the Micro Dot’s own Python library, plus optional example scripts, although for some reason we ended up having to download them manually. Running the flash.py script is recommended first, to check all the pixels are working. Other code examples demonstrate the display’s considerable capabilities and possible uses, including an excellent digital clock, animated bar graph, sine wave, and scrolling text – horizontal and vertical. The comprehensive Python library enables you to light individual pixels; it also includes options to alter brightness to fade text in and out, and use a tiny text mode to write smaller characters, rotated 90°.

While the display’s high number of small pixels results in well-defined digits and letters, which look excellent when shown one per matrix, horizontally scrolling text isn’t quite so easily read due to the gaps between matrices. Other than that, however, this is a very versatile retro-style display and certainly a cut above the standard seven-segment alternative. And since each pair of matrices is driven by an IS31FL3730 chip, talking to the Pi via I2C on addresses 0x61, 0x62, and 0x63, you should be able to use the display alongside many other boards, such as the Enviro pHAT.

Last word

4/5

Apart from the slight difficulty in reading horizontally scrolling text due to the gaps between matrices, this is an excellent, highly versatile retro-style LED display. Superior to seven-segment LED displays, it renders characters in great detail and could come in useful for all manner of projects. You might even be able to play simple games on it, like Pong.

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