Raspberry Pi 4 8Gb version 2 / Raspberry Pi OS 32-bit / Mesa 7c81 / Gecko G540

"I keep telling him to just install the pre-packaged 64-bit SD card image with kernel and application already installed"

@andyrugh Yes, it does run. But it does not have a terminal or internet access to load MesaFlash. So, it does not solve my problem.

Where do you place the 7C81 config files from Mesa?

It really doesn't matter where the firmware files are placed
since they are typically only used once. (when you write firmware
that matches your breakout board)

Note: DO NOT use the file with 'epp' in its name

Thank you PCW for just answering my question.

I know as an enduser of LinuxCNC, I don't make sense to the programmers on this form.

Below are some of my EMC/LinuxCNC machines over the last 18 years.

And some more pictures:

Again, thanks PCW.

I started with a HobbyCNC PRO 4 Axis Kit with EMC, then two DueCore hp and G540 with LinuxCNC.

But the DueCore hard drives are going to give up some time soon. They are over 10 year old IDE drives. So, I though I would upgrade to Raspberry Pi's with remote login like the Duet 3 3d printer board I have.

Once I am done with my upgrade, I will repost every detail on how to install Raspberry Pi 4 8Gb version 2 / Raspberry Pi OS 32-bit / Mesa 7c81 / Gecko G540.  That why you do not need to reexplain over and over to the next enduser. 

@PCW

I can not see the board from the Terminal:
 

Do I need to send both boards back to MESA?  Who should I contact?

You are missing the spi device name (thats what the "bad address" is all about)

sudo mesaflash --device 7c81 --addr /dev/spidev0.0 --spi --readhmid

@PCW
Again, thank you.

But, I still get no board found:
 

open: no such file or directory

means there is no /dev/spidev0.0

which probably means SPI is disabled in the RPI configuration