RPi4 new build, but which Mesa card?

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10 Feb 2021 17:32 #198303 by Hammerbot
I'm starting a new build and have been reading up on how to best use a RPI4 to run a 3-axis CNC router. There seems to be many ways, but is there consensus on which is the best/easiest/ most cost efficient?

1. RPi4 with Mesa 7c80 ($249)
2. RPi4 with Mesa 7i76e ($199)
3. RPi4 with Mesa 7c81 + other BOBs (?) ($89 + $??)

Would like to start with only a router (not a controlled spindle) but can see upgrading in the future.
MPG Pendant is a must, but may need to be an upgrade as well.
Don't know what I don't know yet, but there is so much more to read...

Thanks in advance. Tim

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11 Feb 2021 00:00 #198338 by andypugh
I haven't used any of them but...

The ones that use the expansion connector and SPI should be slightly faster in response and also leave the ethernet port available for networking.
If you were running a plasma cutter then the ethernet card might be preferred for the isolation that ethernet offers.

You can actually use both at the same time, but that would be unusual.

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11 Feb 2021 04:24 #198347 by BeagleBrainz
I'd go with a 7i76e, the only reason being that you are not tied to running an RPi only.
For example if for whatever reason the RPi is not up to your needs...ie you may want to run a CAD\CAM package. Tho not having used a recent RPi ( I had one of the very first models and didn't really do a lot with it) and my RPi 400 is still somewhere but here.

But that is my own opinion. And mine usually suck :laugh:

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11 Feb 2021 06:05 #198354 by Hakan
It will help if you know what your setup will be.
Touch screen? Then most of the io need is gone. Still need limit switches and possibly a probe.
Usb-pendant? Again most of the external buttons are not needed, they are on the pendant. MPG input is not needed, use the wheel on the pendant.
Spindle control? Are there options to the 0-10V like modbus? Most of the vfds have. The a USB-RS485 is typically needed instead. Manual spindle control works fine, I used that all the time on the 3040 router.
Spindle encoder? Not on a router, I don't see a use for that.

So you can end up with only stepper motor output and inputs for e-stop, limit switches and possibly a tool probe.
I'll throw in the 7i96 as an option that I would go for.
Of the options you have listed, the 7c80 seems a bit step imo so a 7c81 + bob (that is laying around here) would be my choice. But all of them work.

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11 Feb 2021 08:03 - 11 Feb 2021 08:06 #198364 by cakeslob
Honestly, if your machine is bigger than a desktop pc, then I recommend using a regular pc. that being said, most of my machines use rpi4s, most of those use 7c81. Ive managed to make some pretty clean panels out of them. setup have been very turnkey thanks to the work of the developers. the last one i made was a new 8gb and all I had to do was plug in the linuxcnc sdcard, and plug the pi4 to the 7c81, and it worked without issue(ini/hal is a different learning curve). for rpi Im gonna have to suggest that, aside from the idea of future proofing your build.
7c81, 7c80 probably to the same effect
-power the rpi4 with the mesa (no usb c needed)
-only uses about 4 io on the pi
-ethernet is free, so you can turn off wifi/bluetooth
-2 sserial ports ( i plan to do pendant/panel with 7i73 to keep wires clean)
-3x 26 pin io , so cheap china breakout board, or 7i76, or whatever
Last edit: 11 Feb 2021 08:06 by cakeslob.
The following user(s) said Thank You: Aciera

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14 Feb 2021 23:02 #198876 by Hammerbot
Thanks all...
I'm leaning towards 7i76e to keep the option of changing back to a PC if it doesn't perform well enough with the Pi.

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22 Feb 2021 22:13 #199775 by jaro_p
I can ask you to publish 7c81 - ini/hal if your knowledge curve has reached its peak?
Unfortunately, my learning curve is dangerously close to zero ...
I would be particularly interested in the solution for cheap china breakout board.
Thanks in advance.

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