LinuxCNC-RIO - RealtimeIO for LinuxCNC based on FPGA (ICE40 / ECP5)

Ok about 24hr later.
Linuxcnc has been idling all that time, run some gcode every now and again, screen goes blank after no input, wiggle the mouse and it wakes up, not a single packet issue.
I'd say it's pretty bloody good. World's better than before.
Thanks so much for the hard work.

Hey guys awesome work so far, I would like to make a PCB for the Tang Nano 9K to plug into, basically a pin for pin copy of meister's Tango board, but with provision for a few extra bits that I'd like. Mainly provision for closed loop control of brushed DC servos.
My plan is to basically copy and paste the line receiver circuitry of my existing servo drives that I've been using for years and use that for the encoder feedback.
My question is which remaining pins on the Tang Nano are best suited for this task ? If possible I'd like a minimum of 5 axis so thats 10 inputs, 15 if we bring a Z pulse for homing/spindle/threading per axis. I realise there's only so many pins to go around but I'd drop a couple of standard inputs off the board if it meant it would all fit.
Also I'd be happy to post the layout once its finished/working and tested for others to use, but be warned I am going to use through hole parts as much as possible, I am old, have bad eyesight and have found out the hard way that through hole PCB's are more resilient to harsh climates, temperatures/humidity etc than PCB's with tiny surface mount parts.

Cheers.
Russell.

Hi Russell,
you just have to pay attention to the HDMI pins and the 1.8V output on BANK3 (you can use it for 3.3V input)

the capacitors on the HDMI output can be remove, but than, you can not use the HDMI-Port anymore on the TanNano9k board.

if you need more pins, you can use shiftregister's, bud not for Highspeed-Encoder or pwm generation (including dir-pins), the shiftregs are very fast but produce some jitter.

@cornholio
thanks for testing, sounds good

new toy

   

www.amazon.de/dp/B07SSL1G18?psc=1&ref=pp...dt_b_product_details

works like a rotary-encoder, i think it should work in RIO

@all

how do you implement differential signals?
i wanted to try it now with the AM26LS32, there are also some from MAX but they are extremely expensive

We use 26LS32's a lot for a couple of reasons:

1. Their inputs are protected from up to +-25V
(the more expensive CMOS parts are typically protected to only +-14V or so)

2. Because they are TTL parts the outputs don't swing to 5V and if you add a 1K
pulldown, the outputs are OK for interfacing with most 3.3V chips.

3. They are much cheaper than  the CMOS equivalents.

The main disadvantage is higher power consumption