Interfacing 100 pulses per rev control knobs

[Neale]

That looks like the way to go. First rule of programming - find someone who has done it already and pinch their code! As the prophet says, pinch one man's work and it's plagiarism, pinch work from lots of people and it's research... Having those libraries available might get me going on my project again.

About 20 years back, I rescued a Weller soldering iron from a scrap bin at work. It had a sticky label saying "display broken" but it turned out to be more than just that. It was quite a fancy temperature-controlled iron with an analogue temperature control, not the more common Weller magnetic bit style with a fixed temperature based on the particular bit you fitted. However, on inspection I reckoned there was a fault on the PCB which was a ceramic board with principal components under beads of something like epoxy. Not much chance of a repair so I ripped it all out and built a new Arduino-based controller using the original pot as an analogue input for temperature setting and an op-amp-based level converter reading the resistance of the temperature sensor somewhere in the iron. There was a triac switching the element (24V) with zero-crossing switching to avoid any transients - although why this worries me is still a mystery as I can't imagine why you would be soldering any sensitive electronics while live. Twiddle the pot and the display shows desired temperature and after a few seconds it goes back to reading actual bit temperature. However, now the pot seems rather noisy and the desired temperature keeps jumping about so the idea is to replace it with a cheap rotary encoder. I have the encoder but still haven't got round to fitting it and updating the code.

[Neale]

In my case, I have spare input ports on my Arduino so no need to emulate a pot - I'm using the pot connected to the Arduino's ADC anyway to give an internal 0-255 to represent desired temperature - so using the processor means a SMOP(*) only needed.

For the Hitachi processor, though, not so sure. Had a quick look at data sheet last night (my, that thing's old!) and it looks as if it has the potential for a couple of interrupt lines but not sure if they would trigger on level change in either direction or just one. I would try to do as much as possible in the CPU and avoid external circuitry, though.

(*) Simple Matter Of Programming

[Robin Hewitt]

I would try to do as much as possible in the CPU and avoid external circuitry, though.

Awww! But I like external circuitry