Mesa 7i92 Encoder wiring

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7 years 2 months ago #141764 by Ralfh
Mesa 7i92 Encoder wiring was created by Ralfh
Hi,
Quick introduction: i'm from germany, student and i like to tinker with DIY-CNCs.
I'm in the process of switching to Linuxcnc. I bought a 7i92 and some cheap Encoders with 600ppr, A and B (no Index) and a open collector output.
Everything seems to work fine:
  • built a custom 7i92 bitfile, the pins are assigned correctly and the jumpers are on default, motors are turning nicely
  • i mapped the encoder A to IO17 and B to IO18
  • i get a signal in halshow on IO17 and IO18 pins if i apply 5V
  • i get a 5V output signal of the encoder using a pullup (10k) without connecting it to the 7i92

Here is my problem:
I can't get a signal in Linuxcnc if i connect the encoder to the 7i92.
  • if i don't use a external pullup i measure 48V on the Pin (????)
  • if i use a external pullup i measure 0V

A few questions i couldn't find in the 7i92 manual:
  • how much current does the input of the 7i92 has to get to detect a signal? my pullup may be too big..
  • do i have to activate the internal pullups to function? i guessed Jumper W1 is responsible

I hope someone can help. I will try a few different pullups, maybe i'm lucky and find a right one ( i don't have a spare potentiometer to try, this will take some time :laugh: )

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7 years 2 months ago #141769 by tommylight
Replied by tommylight on topic Mesa 7i92 Encoder wiring
Since they are FPGA pins i would assume there is very little current needed to be detected.
There should also be no need for pullups as the 7i92 will have all pins high when it is powered on untill linuxcnc starts and there are hal entries commanding it to bring them low.
The main thing to check is there should be entries in hal to tell the pins what they are supposed to do, like gpio018_is_input etc.
Also check what is assigned to what pin, with mesaflash.

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7 years 2 months ago #141776 by PCW
Replied by PCW on topic Mesa 7i92 Encoder wiring
7I92 inputs have 4.7K pullups and if the 7I92 is set for 5V tolerance
the inputs will have the pullup resistor common connected to +5V
So the pullup current is ~1 ma ( page 14 in the 7I92 manual )

I hope you mean you measured 4.8V, not 48V...

Pins that are inputs or disabled output functions (Stepgens etc)
should be high (5V) if unconnected so can be checked by grounding

When testing, make sure that you ground to the 7I92 ground, _NOT_
frame grounds or other system grounds as its easy to damage the
Busswitch protection diodes with inputs more negative than -0.6V
if there is no current limiting. (and its very common to have
HF AC ground differences of more than 0.6V where Step/Servo/VFD drives
are present)

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7 years 2 months ago #141777 by Ralfh
Replied by Ralfh on topic Mesa 7i92 Encoder wiring
Seriously, i measured 48,3V and was very confused. I could verify that the Input is still working by applying 5V, halshow showed it correctly.

I got my .hal with pncconf (attached), readhmid should be ok:

Code:
IO Connections for P2 Pin# I/O Pri. func Sec. func Chan Pin func Pin Dir 1 0 IOPort PWM 0 PWM (Out) 14 1 IOPort None 2 2 IOPort StepGen 0 Step/Table1 (Out) 15 3 IOPort None 3 4 IOPort StepGen 0 Dir/Table2 (Out) 16 5 IOPort StepGen 4 Step/Table1 (Out) 4 6 IOPort StepGen 1 Step/Table1 (Out) 17 7 IOPort StepGen 4 Dir/Table2 (Out) 5 8 IOPort StepGen 1 Dir/Table2 (Out) 6 9 IOPort StepGen 2 Step/Table1 (Out) 7 10 IOPort StepGen 2 Dir/Table2 (Out) 8 11 IOPort StepGen 3 Step/Table1 (Out) 9 12 IOPort StepGen 3 Dir/Table2 (Out) 10 13 IOPort None 11 14 IOPort None 12 15 IOPort None 13 16 IOPort None IO Connections for P1 Pin# I/O Pri. func Sec. func Chan Pin func Pin Dir 1 17 IOPort QCount 0 Quad-A (In) 14 18 IOPort QCount 0 Quad-B (In) 2 19 IOPort QCount 0 Quad-IDX (In) 15 20 IOPort QCount 1 Quad-A (In) 3 21 IOPort QCount 1 Quad-B (In) 16 22 IOPort QCount 1 Quad-IDX (In) 4 23 IOPort QCount 2 Quad-A (In) 17 24 IOPort QCount 2 Quad-B (In) 5 25 IOPort QCount 2 Quad-IDX (In) 6 26 IOPort QCount 3 Quad-A (In) 7 27 IOPort QCount 3 Quad-B (In) 8 28 IOPort QCount 3 Quad-IDX (In) 9 29 IOPort None 10 30 IOPort None 11 31 IOPort None 12 32 IOPort None 13 33 IOPort None

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7 years 2 months ago #141780 by PCW
Replied by PCW on topic Mesa 7i92 Encoder wiring
You should never have to apply 5V to an input for it to be detected as high.
Inputs should always be high if not driven by the FPGA or external sources

If you simply power a 7I92 (no LinuxCNC no connections)
and measure all the I/O pins, they should all be high, if not,
the card has been damaged

(which does unfortunately sound likely if you have 48V anywhere near the 7I92 card)

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7 years 2 months ago #141786 by Ralfh
Replied by Ralfh on topic Mesa 7i92 Encoder wiring
Nice, the 5V are still present on 15 pins. A few are broken but I could finally test the encoder. Thanks for the help!

I might have broken these pins while I wired the encoder up but didn’t power down the encoder PSU..

If I connect everything i need I still have about 5 pins left. It’s not dramatic. I just feel dumb breaking something before even using it

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7 years 2 months ago #141788 by PCW
Replied by PCW on topic Mesa 7i92 Encoder wiring
When testing hardware connected to bare FPGA pins, one really important thing is to
make sure that there is a common ground connected first. This is especially important when you have floating power supplies like cell phone chargers etc that have no earth ground. These can have a 100V or more potential voltage if you measure to earth ground (basically Leakage current but with enough capacitance to ground to damage IC inputs)

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7 years 2 months ago #141858 by Ralfh
Replied by Ralfh on topic Mesa 7i92 Encoder wiring
So, i built a new .BIT with alternative pins:
Code:
IO Connections for P2 Pin# I/O Pri. func Sec. func Chan Pin func Pin Dir 1 0 IOPort PWM 0 PWM (Out) 14 1 IOPort None 2 2 IOPort StepGen 0 Step/Table1 (Out) 15 3 IOPort None 3 4 IOPort StepGen 0 Dir/Table2 (Out) 16 5 IOPort StepGen 4 Step/Table1 (Out) 4 6 IOPort StepGen 1 Step/Table1 (Out) 17 7 IOPort StepGen 4 Dir/Table2 (Out) 5 8 IOPort StepGen 1 Dir/Table2 (Out) 6 9 IOPort StepGen 2 Step/Table1 (Out) 7 10 IOPort StepGen 2 Dir/Table2 (Out) 8 11 IOPort StepGen 3 Step/Table1 (Out) 9 12 IOPort StepGen 3 Dir/Table2 (Out) 10 13 IOPort None 11 14 IOPort None 12 15 IOPort None 13 16 IOPort None IO Connections for P1 Pin# I/O Pri. func Sec. func Chan Pin func Pin Dir 1 17 IOPort None 14 18 IOPort None 2 19 IOPort None 15 20 IOPort None 3 21 IOPort QCount 0 Quad-A (In) 16 22 IOPort None 4 23 IOPort QCount 0 Quad-B (In) 17 24 IOPort None 5 25 IOPort QCount 0 Quad-IDX (In) 6 26 IOPort QCount 1 Quad-A (In) 7 27 IOPort QCount 1 Quad-B (In) 8 28 IOPort QCount 1 Quad-IDX (In) 9 29 IOPort QCount 2 Quad-A (In) 10 30 IOPort QCount 2 Quad-B (In) 11 31 IOPort QCount 2 Quad-IDX (In) 12 32 IOPort None 13 33 IOPort None

i verified and attached the .bit if someone wants to use it.

Attachment not found

You can sudo-copy the .xml to /lib/firmwares/hm2/ to create your .hal with pncconf.

Attachment not found



Also i found out how i bricked the pins. I got a Breakoutboard to connect wires to the DB25 connector via screw terminals. I connected all the GND wires on the Terminal "GND", but with the flat cable connection to the mesa board this screw terminal is NOT connected. I should have known that, since i crimped the cable. i will wire a cable to a functioning ground to never make that mistake again.

Attachment not found

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