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Chap builds rotary dial mobile phone

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If you miss the whirr-and-thunk of a rotary dial, you could download an app that imitates the rotary dialler, or you could make your own mobile with a rotary dial.

For those that prefer something a little more physical, this Hackaday project should keep you busy with the soldering iron: a real rotary dialler (with appropriate interface to a GSM module for the phone) as a DIY.

It was created as a competition entry for the NXP LPC810 Challenge, which asked entrants how much they can get out of an ARM Cortex M0+ microcontroller – one that only has an eight pin package.

With so little available to control a GSM module, the project's author “Jaromir” had to handle I/O. As he writes at his blog, it's “not that complicated”. He used a UART and “a few I/O lines”, and spent a lot of time writing a “decent parser of AT commands – that can be [a] nightmare”.

A 74HC164 shift register cut the required number of pins down from the 12-16 needed to the six lines available from the microcontroller. These six I/O lines handle the input from the rotary dial, output to the display, and a serial line to the GSM module.

As Hackaday notes, it's “a somewhat impressive demonstration of using a shift register as both an input and output expander at the same time”.

Still on his to-do list are things like toggling the DTR line, a power-save mode, and a CLIP function to display a caller's ID.

Here's a video of the rotary dialler in action:

Youtube Video

Jaromir has published the hardware design files on his site, with the software at github here. ®

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