Raspberry Pi 4 with Mesa 7c81

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12 Apr 2021 08:38 #205711 by jaro_p
Can anyone please help with creating a bitfile?
I downloaded data from .mesanet.com.
I tried to create a bitfile using ISE Project Navigator, first in version 14.5 (P.58f), then in version 14.7 (P.20160913) for windows 10.
I tried to create a bitfile for different breakout boards. I did not make any changes, I used the original files. The process will always run with the message "completed successfully", but a bitfile will never be created.
I would need a bitfile for 7i78. I modified the file for 5i25. I don't know if this file is OK or what needs to be changed.
When creating the bitfile, I followed this gentleman - probably the best that can be found.


Thank you in advance for any advice.
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12 Apr 2021 11:58 #205717 by PCW
Replied by PCW on topic Raspberry Pi 4 with Mesa 7c81
Here is a bitfile for a 7C81 and 1 or 2 7I78s:

File Attachment:

File Name: 7c81_7i78x2d.zip
File Size:110 KB


I have included the pinout file

If you are experimenting with making bitfiles, you should write them to the
fallback location on the cards flash memory, not the user location, because
if there is an error in your bitfile, you can brick the card. If you write the test bitfile to the
fallback location, you can just power cycle the card to get back to a working
configuration, rather than needing JTAG programmer to recover.
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12 Apr 2021 13:21 #205718 by jaro_p
Thanks and I'm going for it.

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12 Apr 2021 19:00 #205729 by jaro_p
Unfortunately, after the --readhmid command, I only get the message:
unable to set bpw32, fallback to bpw8
I tried to write the configuration:

mesaflash --device 7c81 --addr /dev/spidev0.0 --spi --fallback --write /home/pi/Downloads/7c81/7c81_7i78x2d.bit

unable to set bpw32, fallback to bpw8

Checking file... OK
File type: BIT file
Boot sector OK
EEPROM sectors to write: 6, max sectors in area: 15
Erasing EEPROM sectors starting from 0x10000...
|EEEEEE
Programming EEPROM sectors starting from 0x10000...
|WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW
Board configuration updated successfully.
Checking file... OK
File type: BIT file
Boot sector OK
Verifying EEPROM sectors starting from 0x10000...
|VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
Board configuration verified successfully.

You must power cycle the hardware or use the --reload command to load a new firmware.

root@raspicnc-7c81:~# mesaflash --device 7c81 --addr /dev/spidev0.0 --spi --reload

unable to set bpw32, fallback to bpw8
Waiting for FPGA configuration...OK

root@raspicnc-7c81:~# mesaflash --device 7c81 --addr /dev/spidev0.0 --spi readhmid

unable to set bpw32, fallback to bpw8

What does it mean? Why can't I read eeprom?
After the reboot, I only get the message again:
unable to set bpw32, fallback to bpw8

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12 Apr 2021 19:23 #205730 by PCW
Replied by PCW on topic Raspberry Pi 4 with Mesa 7c81
The

unable to set bpw32, fallback to bpw8

message is harmless is just means the RPIs SPI interface cannot do 32 bit transfers
so mesaflash uses 8 bit transfers instead

I dont know why readhmid is not working but note, you are not using the new configuration.
To test a new configuration that has been written to the fallback area of the EEPROM, you would:

mesaflash --device 7c81 --addr /dev/spidev0.0 --spi --fallback --reload 

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12 Apr 2021 20:02 #205732 by jaro_p
That's what I did - it's my eighth line from the bottom.

root@raspicnc-7c81:~# mesaflash --device 7c81 --addr /dev/spidev0.0 --spi --reload

unable to set bpw32, fallback to bpw8
...

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12 Apr 2021 20:17 - 12 Apr 2021 20:23 #205733 by PCW
Replied by PCW on topic Raspberry Pi 4 with Mesa 7c81
No, you did --reload , not --fallback --reload

-- reload by itself will load the FPGA from the user configuration area of the flash EEPROM
--fallback --reload will load the FPGA from the fallback area of the flash EEPROM
Last edit: 12 Apr 2021 20:23 by PCW.

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12 Apr 2021 21:59 #205738 by jaro_p
Ok - sorry. When I use --fallback --reload, I finally get a configuration listing.
After the restart, the configuration is finally listed normally, ie without the --fallback command, only readhmid.

Thank you, I really appreciate your help.

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12 Apr 2021 22:19 - 12 Apr 2021 22:21 #205743 by PCW
Replied by PCW on topic Raspberry Pi 4 with Mesa 7c81
Note that if you have only loaded the 7i78 configuration in the fallback area
it will only be used if you load the FPGA from it with mesaflash --fallback --reload
and it will only persist until a power cycle. This makes it valuable for testing
unknown bitfiles. If the new bitfile works, then you can write it to the user configuration
area of the flash (no --fallback).

If you load a bad bitfile into the fallback area when testing,
make sure to re-write the falllback area with a working bitfile
(default is 7c81_fallback.bit)

The fallback configuration is used when the user configuration
fails to load because its corrupted in some way. For example
if you write a bitfile to the 7C81 and have a crash in the middle of
writing the flash, at the next power cycle, the FPGA will attempt
to load the user configuration but will fail (it will detect a CRC error)
In this case, the FPGA will attempt to load the fallback configuration
so it important to have a working fallback configuration in the EEPROM
Last edit: 12 Apr 2021 22:21 by PCW.

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08 Oct 2021 21:28 #222588 by maurice
Hello. Complete novice here.

I have gotten my hands on a 7C81 and I want to connect my closed loop steppers directly it.

From what I have seen on the fourms, this is a more unusual setup, and I will need to make and flash a custom bitfile to my board.
My understanding is that I will need PWM + 3StepGens + 3QCounts.

The -readhmid output from the default bitfile has one QCount with A, B, IDX, but my encoders have differential output. A+,A-,B+,B-
Is this something I can configure my custom bitfile to accept? Or will I need 6 QCounts and some software layer? Or simply ground the negatives? I saw that the 7i78 has accepts a differential encoder input.

Many thanks in advance.

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