Low Cost Raspberry Pi Contoller Board

I'm running a 7i96e Mesa card on my CNC router and am very happy with it.  But I'm thing it is over kill and lacks a channel.

For a hobby/educational project I need 5 stepper channels and a servo channel.  I was thinking of using a Raspberry Pi 4 or 5.

What would be the cheapest option for a LinucCNC compatible card driven off a Pi?  What are the options today?

RPi4 can do ethernet, gpio & SPI

RPI5 can do ethernet, maybe able to do gpio can't do SPI (no idea if or when that will happen)

You would have to check availability of 7i90, 7c80 & 7c81 for RPI4 Spi at Mesa.

I've been experimenting with some FPGA dev boards I've bought from Aliexpress that run 7c81 firmware, & a customised firmware.

Here's an example of what I've done.
forum.linuxcnc.org/show-your-stuff/51142...pga-card-9d60#289226

There's also a couple of projects such as:
github.com/multigcs/LinuxCNC-RIO SPI or Ethernet
github.com/sensille/litehm2

I don't know if the Remora project has the IO you need.

Bit of a warning tho, litehm2 requires some modding of the board.
LinuxcncRIO requires the building of external board to get 3.3v to 5v translation.
My own project requires that as well, but has been designed to work with standard parallel port Bob and mesa DB25 daughter boards & smart serial, tho does require a RS-422 board, cheap as chips from Aliexpress.
At the end of the day the "roll your own boards" can get close to the cost of a genuine Mesa board.
If the 7i90 were available I'd go that way, about the cheapest Mesa board you can get & has 72 IO only "issue" is that the IO connector is not DB25 compatible but I think there is an adapter available, 7c81 would be next as it makes a compact unit with the RPi4, but requires a breakout board between it and you hardware.

At the end of the day it really pays to work out the cost of the board itself & any any items needed to connect to your electronics, sometimes what does look expensive turns out to be cheaper in the long run.

What is a "servo channel"?

Hi means an output for RC-Servos

meister wrote:

Hi means an output for RC-Servos

Yes, exactly, a three wire RC servo to control the gripper.  I overlooked how to control this pseudo axis.

ok cool, if its RC servos, check out remora

github.com/scottalford75/Remora

remora-docs.readthedocs.io/en/latest/

and since im here, shameless self plug for an ultra low cost educational cnc controller

github.com/cakeslob/RRW_LAB

Tommy I can actually believe that, but those prices look really high for both models. The RPi5 "broke" a lot of what works with the RPi4, especially if you want to play with gpios.

dont worry tommy, you can use ethernet also

tommylight wrote:

Normally i would ask "where is the price", but given the current state of RPI exorbitant prices, i am skipping it for the foreseeable future. :
This is the current actual pricing here, see if you can spot a glaring issue:

The prices of that supplier are exaggerated.
This is the site of a distributor in Italy  (www.melopero.com/shop/raspberry-pi/raspberry-pi-5-8gb/)