Raspberry Pi 4 with Mesa 7c81

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16 Jan 2024 02:50 #290824 by PCW
Replied by PCW on topic Raspberry Pi 4 with Mesa 7c81
Typically you would use a breakout board like the common "5 Axis Mach" BOB
and not connect directly to the 7C81s ports

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16 Jan 2024 11:24 #290856 by andypugh

The current gap I’m trying to fill is how to get from the Mesa 7c81 board to the 5 StepperOnline DM542Ts (Spindle, X, Z, A, & C).  In particular, I am at a loss on how to get the 3 needed signals to the DM542Ts:  Step, Direction, & Enable. 

I am seeking some guidance on where to find instructions or manuals which can me help get started.  I recognize that this is probably a very basic set of questions, so I appreciate whatever help can be provided to point me in the right direction. 

 

Have you found the 7C81 manual?  www.mesanet.com/pdf/parallel/7c81man.pdf

Though admittedly that doesn't really answer your questions, because the functions of the various chips depends on the firmware flashed to the 7c81. 

There are a number of possible firmwares, but it is probable that the one you have is good enough for your purposes. 

There are two ways to identify which signals are on each header pin of the 7C81. You can use mesaflash, or you can run a LinuxCNC HAL command line session. 

Starting with the HAL method, this will also check that LinuxCNC comms to the board are working. 

Open a terminal. 
halrun
loadrt hostmot2
loadrt hm2_rpspi

If all it well, this should connect to the Mesa board, and give you a list of what function is on which IO pin. 

You can then continue with additional HAL commands, for example 
show pin

When finished:
exit

The other way is with mesaflash. You might need to install this: "sudo apt-get install mesaflash"
mesaflash --spi --device 7c81 --readhmid

(This might need to tbe "sudo mesaflash")

Report back what the results are, there are a number of possible hurdles to either of these working immediately. 

 

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16 Jan 2024 14:38 #290873 by PCW
Replied by PCW on topic Raspberry Pi 4 with Mesa 7c81
The default 7C81 firmware is 5ABOBx3 which is compatible
with the common Mach 5 Axis BOBs

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16 Jan 2024 14:55 #290874 by andypugh
IO Connections for P1+Serial
Pin#  I/O   Pri. func    Sec. func       Chan      Pin func        Pin Dir

 0      0   IOPort       PWM              0        PWM             (Out)
 0      1   IOPort       None           
 0      2   IOPort       StepGen          0        Step/Table1     (Out)
 0      3   IOPort       None           
 0      4   IOPort       StepGen          0        Dir/Table2      (Out)
 0      5   IOPort       None           
 0      6   IOPort       StepGen          1        Step/Table1     (Out)
 0      7   IOPort       None           
 0      8   IOPort       StepGen          1        Dir/Table2      (Out)
 0      9   IOPort       StepGen          2        Step/Table1     (Out)
 0     10   IOPort       StepGen          2        Dir/Table2      (Out)
 0     11   IOPort       StepGen          3        Step/Table1     (Out)
 0     12   IOPort       StepGen          3        Dir/Table2      (Out)
 0     13   IOPort       None           
 0     14   IOPort       QCount           0        Quad-A          (In)
 0     15   IOPort       QCount           0        Quad-B          (In)
 0     16   IOPort       QCount           0        Quad-IDX        (In)
 0     17   IOPort       None           
 0     18   IOPort       None           

IO Connections for P2+Serial
Pin#  I/O   Pri. func    Sec. func       Chan      Pin func        Pin Dir

 0     19   IOPort       PWM              1        PWM             (Out)
 0     20   IOPort       None           
 0     21   IOPort       StepGen          4        Step/Table1     (Out)
 0     22   IOPort       None           
 0     23   IOPort       StepGen          4        Dir/Table2      (Out)
 0     24   IOPort       None           
 0     25   IOPort       StepGen          5        Step/Table1     (Out)
 0     26   IOPort       None           
 0     27   IOPort       StepGen          5        Dir/Table2      (Out)
 0     28   IOPort       StepGen          6        Step/Table1     (Out)
 0     29   IOPort       StepGen          6        Dir/Table2      (Out)
 0     30   IOPort       StepGen          7        Step/Table1     (Out)
 0     31   IOPort       StepGen          7        Dir/Table2      (Out)
 0     32   IOPort       None           
 0     33   IOPort       QCount           1        Quad-A          (In)
 0     34   IOPort       QCount           1        Quad-B          (In)
 0     35   IOPort       QCount           1        Quad-IDX        (In)
 0     36   IOPort       None           
 0     37   IOPort       None           

IO Connections for P7+Serial
Pin#  I/O   Pri. func    Sec. func       Chan      Pin func        Pin Dir

 0     38   IOPort       PWM              2        PWM             (Out)
 0     39   IOPort       None           
 0     40   IOPort       StepGen          8        Step/Table1     (Out)
 0     41   IOPort       None           
 0     42   IOPort       StepGen          8        Dir/Table2      (Out)
 0     43   IOPort       None           
 0     44   IOPort       StepGen          9        Step/Table1     (Out)
 0     45   IOPort       None           
 0     46   IOPort       StepGen          9        Dir/Table2      (Out)
 0     47   IOPort       StepGen         10        Step/Table1     (Out)
 0     48   IOPort       StepGen         10        Dir/Table2      (Out)
 0     49   IOPort       StepGen         11        Step/Table1     (Out)
 0     50   IOPort       StepGen         11        Dir/Table2      (Out)
 0     51   IOPort       None           
 0     52   IOPort       QCount           2        Quad-A          (In)
 0     53   IOPort       QCount           2        Quad-B          (In)
 0     54   IOPort       QCount           2        Quad-IDX        (In)
 0     55   IOPort       None           
 0     56   IOPort       None           

It looks like you will have to use the manual to map the physical pin numbers to IO numbers to find where each signal is, which is slightly unfortunate.

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16 Jan 2024 15:19 - 16 Jan 2024 16:05 #290876 by PCW
Replied by PCW on topic Raspberry Pi 4 with Mesa 7c81
Is that the latest mesaflash?

(current mesaflash should print the 7C81 pinouts correctly)
Last edit: 16 Jan 2024 16:05 by PCW.

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29 Feb 2024 21:20 #294802 by richcolvin
I have received the two Sain Smart 5-Axis CNC Break Out Boards (ST-V3) which connected easily to the Mesa 7C81. 

When I connect these BOBs to the StepperOnline DM542T drivers, it seems that the common connection is +5V, not GND.  Does it seem right that it would be connected this way?

BOB                    DM542T
+5V                      PULse +
                             ENAble +
                             DIRection +

ENable                ENAble -

DIRection           DIRection -

STEP                    PULse -

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29 Feb 2024 21:22 #294803 by richcolvin
Regarding the Sain Smart 5-Axis CNC Break Out Boards (ST-V3)  and lathe spindle, is the A axis used for the spindle?  Or is that somehow configured in LinuxCNC?

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29 Feb 2024 21:43 #294804 by PCW
Replied by PCW on topic Raspberry Pi 4 with Mesa 7c81
1, You can wire the drives with either
common ground:
= drive step-/dir- --> GND,  BOB step/dir --> drive step+,dir+
or common +5V:
= drive step+,dir+ --> 5V, BOB step/dir --> drive step-,dir-

If you use common 5V, you must invert the step outputs
as they are now active low

Typically you would not use an axis for the spindle


 

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