We are gonna have a bad time with E-Waste with all
these
smartphones going outdated soon.
Most of them have the commonality of having an audio
port. And sometimes a usb port.
So why not repurpose these smartphones as OCR
scanners,
for barcodes like QR codes.
Just output the code over
a serial port via audio or usb.
As
for the display, you could display QR codes, if needed as
well.
The cable could be a typical usb that simulates a serial
host, or an audio port that outputs serial signal.
The serial signal can then be read directly for
custom/embedded systems, or can simulate a usb
keyboard
for easy entry of data for the common user.
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Keeping everything as 'serial', also will reduce vectors for
exploits.
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Could allow wifi connection, but might be safer to just
disable it entirely.
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Serial :- Old school UART