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Drumroll - Yet Another Picaxe

If Swan's 2nd Law is: "Microcontrollers can never have too many I/O channels" . . . what's his first?

By Stan Swan

Although PICAXE microcontrollers are now well established and popular in numerous electronic projects, due in no small part to SILICON CHIP’s enthusiasm, many users know only of the entry level 08M, versatile 18X or powerful 28X.

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The three "M" PICAXES are very similar in pinouts and architecture, meaning little change in code as you move up the chain (in fact, the 08M is pin-for-pin for the top eight of the 14M). The main difference is all those beautiful extra inputs and output channels!

However, the recent arrival of a 20-pin PICAXE now takes the family to an awesome 14 members, although four earlier offerings are now discontinued and two "X2" fire breathers have yet to be released. This new PICAXE-20M (based upon a MicroChip PIC16F677) is really just a stretched 08M, as it offers similar memory and follows the same commands as the ever popular 08M and more recent 14M.

Thankfully, its 10-a-side DIP packaging enables easier identification in the sea of chips lurking in many IC parts drawers, since its 20 pins make it noticeably longer than common 14,16 or even 18-pin DIP logic ICs.

The so-called 20M is mainly intended to meet the demand for further input and output (I/Os) channels than the four offered by the smaller 08M, or 5-6 of the 14M.

Its provision of eight I/Os, arranged with inputs (0-7) on one side and outputs (0-7) on the other, looks to have strong appeal for projects where extra chips (such as Shift Registers) and wiring would otherwise be needed.

Circuit size will naturally be reduced with just a single IC, yet greater flexibility will result, thanks of course to the PICAXE programmable features.

All three "M" chips are especially well-suited for hobbyists and educational users, allowing enhanced design for just a few dollars more, when the need for extra I/O channels arises.

Pleasingly, the larger 14 and 20 "M" offerings retain the same programming and supply connections as the classic 08M, although only the 08M allows pins to be set either as Inputs or Outputs.

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