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The Rotary Cell Phone


It’s happened. It’s finally happened. In a move that has hipsters donning their good flannel and breaking out that case of Genesee they were saving for a special occasion, the rotary cell phone is now a reality.

[Jaromir] created this astonishingly retro future device as an entry for the NXP LPC810 challenge, a contest to do the most with an ARM Cortex M0+ microcontroller in an 8-pin package. Having only six I/O pins for controlling a GSM module, display a few buttons, and the fancy rotary dial meant [Jaromir] needed to expand his I/O some way. He chose a shift register to handle the buttons and display in a somewhat impressive demonstration of using a shift register as both an input and output expander at the same time.

From the videos [Jaromir] uploaded, the rotary cell phone isn’t ready for Think Geek to do a production run quite yet. He needs to enter the PIN for the SIM card, AT commands for the GSM module, and is, of course, a horrible method of user input for the younglings who have only seen rotary phones in old movies. That being said, it’s a rotary cell phone running on an 8-pin microcontroller. What more do you want?

Videos of this awesome this truly awesome phone in action below. If you’d like to build your own – and why wouldn’t you – all the files are available on [Jaromir]‘s git

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Rotary dial authenticates sudo commands

[W1ndman] won’t win any security awards for this build, but it’s an interesting idea. On many Linux-based systems commands can be run with administrator privileges by prefacing them with the keyword ‘sudo’. Normally you’d be asked for a password but [W1ndman] used the Pluggable Authentication Modules (PAM) to authenticate via his own shell script. That script checks a code from this rotary dial for authentication. An Arduino takes care of listening for each digit that is entered and then sends the code via USB for comparison with a stored file. We’re not sure if that stored code is in a plain file or is otherwise protected, but at the very least this prevents you from using ‘sudo’ willy-nilly.


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