Backing up HP28s user data via IR port

[EugeneNine]

so its been a few years but I would send IR from my 48sx to various pc's over serial. The trick is most bought IR adapters have a small mcu in them which 'speaks' IRDA and the HP's don't. You have to build your own by just connecting an IR tx/rx pair to the serial port. Its been many years but I'd use one of the IR pair sets Radio Shack sold and a rs232 level shifter like the max232.
Now a days I'm using a USB-rs232 but going from usb 5v to +/-12v for rs232 and then back to 5v for the ir pair is overkill, it would be easier to use one of the USB-serial @5v or 3.3v like what are used for programming small mcu' like Arduino and such. I should still have some parts lying around to test with.