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Comment by to3m | Hacker News Reader

One nice thing about the PC's parallel port was that it was bidirectional, relatively straightforward to program, could be programmed at a reasonable rate, and supplies/accepts a standard TTL +0V/+5V. This allows interfacing with a reasonable range of devices using a cable that's relatively simple to make up. Doing the same thing over USB is possible, but you need a microcontroller, which means more programming (i.e., more things to go wrong).

But this isn't a common problem. I don't rue the passing of all the nonsense that USB replaced.

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It's kind of boggling to read project blogs from people messing with Arduinos and Raspberry Pis and, after all the unpacking and setup and breadboarding and programming, they can finally light up an LED as their hello world.

When we had basic PCs and parallel port you could literally take a resistor + LED, twist them together, stick it into the parallel port itself and with a line or two of MS-DOS shell script make it light up.

Well, it is for good reason that multi-user operating systems don't permit arbitrary processes to do port IO. That said, if all you want to do is poke the LEDs on an arm board, dd to /dev/mem as root will probably do the trick.

and if you replaced the LED for a speaker, and created a resistor ladder, you could squirt data out the parallel port and get sound.

The NO$GB emulator used this, for example. And even though it was horrible it was authentically horrible.

Those were actually sold commercially, too - as the "Covox Speech Thing". This meant that home-made parallel port resistor ladder DAC was supported in many games.

It's pretty amazing what we managed to attach to the humble parallel port. My first CD burner was a big parallel port device.

Oh the memories of buffer underruns.

"DON'T touch the computer it's burning a CD!"

Don't even walk on the floor near it or you'll shake it and ruin the burn.

The fact that the parallel port was the only high speed bidirectional port also lead to attempts to daisy chain things that usually didn't work past a device or two. So you may have an external drive or a scanner and your printer and if you were lucky you could leave it all plugged together and it would work.

I also remember being short of COM ports between modems, drawing tablets, special game controllers that didn't use the joystick port, etc. Installing a serial card for additional ports was one of my first upgrades.

still, that occasional use case is catered for with a USB breakout board, or a USB to serial. So it's not like we have really lost anything

Except for the "reasonable rate" bit, which (IMHO) also includes "reasonable latency." Real UARTs can be used for, e.g., pulse-per-second inputs from GPS or atomic clocks to discipline an NTP server. That doesn't work for a USB->serial thingy (because the latency is literally three orders of magnitude worse).

It doesn't always work.

I've seen serial devices that are so picky with timing that they'll work with real serial ports but most USB->Serial adapters cause programming to fail.

And let's not forget the 80% of USB->Serial adapters that are using counterfeit FTDI chips and barely work at all, if you can get an O/S to recognize it.

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