Your outline of your chip selection process was very helpful..I mean I am still terrible at it, but at least that process minimizes my frustration. I have started building the circuit, got most of the basics done (pwr connections, oscillator, ect)

I was just starting to work out the 5->3.3 voltage dividers when I remembered the encoder signal goes straight into the driver. So i popped open the data sheet, confirming those signals do go into the driver. Now there are internal connections between the original computer & the driver rack, so maybe its just a passthrough.... Then looking at the block diagram (see page 14), there are several indications of +-12v. And on page 16(pinout), there are two pins labeled +-12v OUT. (Other where refereed to as AUX voltage). Thought these might be the Monitors (I & N), but those are separate outputs on the pin out. I am have a bit of trouble understanding the flow and what is happening, but I think there is at least a chance that driver itself was handling the PID. From the block diagram, we see the encoders go into Frequency -> voltage converter (not familiar with those) and then become -Tacho input. All I can work out for sure is that the driver itself was doing SOMETHING with the encoder signals....Can you shed some light as to what is happening there?

the encoders have A, B and I outputs (as well as there inverted compliments). The "I" channel is just 1 div / rotation. The driver does not seem to use this (or even bring it in as an input), but in theory, this sounds like a useful feature to ensure there were no missed divisions on the encoder. But theory doesn't always match up to practical applications, and I have no experience with that. So I turn to you for advice.


re: programming header - how does this connect to the computer? Its been a long time since I have tried anything with that, but I recall making a header -> serial cable. So do I need to buy / make a cable for this? And then what software to flash the chip (i think atmel studio? ) Then once the bootloader is flashed, I can upload sketches through usb like a normal arduino? Also curious what you write code in? The arduino IDE is cute, simple & great for beginners...but kind of useless for building sizeable projects. I had switched to Sloeber, which is built inside eclipse. I went with it because I knew the interface a little bit from some JAVA programing I did. So what do you recommend?