Can't configure Mesa 7i92

There are ( at least ) 2 ways to reverse axis direction depending on whether the machine coordinates are correct
(That is does the DRO read correctly)

If the DRO reads correctly the easiest way is to invert the DIR pin

Inverting the direction pin requires setting the invert_output parameter for the proper GPIO pin
You can determine the specific GPIO pin(s) to invert by looking at the pinout that
mesaflash --device 7i92 --addr 10.10.10.10 --readhmid
returns

for example:

setp hm2_[HOSTMOT2](BOARD).0.gpio.004.invert_output true

will invert a g540 configs stepgen 0 direction pin

If the DRO reads in the wrong direction you change the SCALE parameter in the INI file

I think LinuxCNCs main focus has been milling machines and lathes and its
less used on routers, plasma cutters and the like that are likely to use dual drive gantry configs

You might open a new thread on gantry homing and see how others deal with it

OK, got it moving, and the directions are correct-

Now, though, I have 2 weird problems:

1. The stepper is VERY noisy at lower speeds on the Z axis and X axis (which moves the whole gantry, of which only one side works). Weirdly the Y does NOT make any unusual sound, and it's the SAME physical rack-and-pinion as the X. I checked the .INI file and the info for the X and Y are identical. The Z is a leadscrew, totally different, but makes the same noise as the X. It doesn't matter if it's a manual jog at 60ipm or an MDI command at 60ipm, it moves but makes a LOT of rattle/grinding sound. It goes away with a faster move.

2. The second X-gantry motor isn't just unstepped, it's unpowered. This I can't understand- this a G540, there's no way to disconnect power, it should be locked in place in the absence of a STEP pulse. I know the current drops to 70% of its rating when it's idle for a few seconds, but this is much weaker than that. The unpowered side is actually being dragged by the powered side so there's no current to speak of. I'm baffled, it didn't do this on the Ethernet Smoothstepper, and the motor wiring hasn't been touched.

EDIT: ok, I think the noise is from the G540 itself being poorly tuned- LinuxCNC was jogging at 60ipm, a speed I basically never used in Mach3.

I found something odd, though. I went to change my timing parameters to match the G540 limits- STEP 1000ns high, 2000ns low, DIR 200ns setup/hold

What I got was the axis stopped working entirely when STEP was below about 2300 ns HIGH. Stopped working entirely. Is that just due to a weak output being too slow? It this an open collector output?

Basic calcs are showing me I don't need less than a 28us total STEP period so I guess that's not a thing.

As far as timing goes, in my experience the G540 timing specs are not valid at 3.3V.
I would use 2.5 or even 5 usec for step timing, as there is no disadvantage of longer pulses
until they limit your maximum step rate.

The 7I92 outputs are 3.3V push pull signals with 24 mA of drive and > 50MHZ bandwidth
(they can be programmed for open-drain mode but that is not the default)

For the 4th axis issue, you might try enabling the 4th step generator in the .ini file, the
4th axis G540 pins will be both weakly pulled high if only 3 axis are enabled
(since they will be inputs if not enabled as stepgens) and this might cause strange behavior

Hi all..

I'm currently trying to decide between the 7i92 and the 5i25. I'm tempted by the 7i92 because I could connect to an existing LAN port, but have slight hesitation since support has only just been added to LinuxCNC (AFAIK).

Are there any pros/cons between the two regarding performance and reliability etc?

I've always struggled to find a PC that could provide a low base thread times. Will these Mesa cards allow me to run PC hardware independent of the CPU base thread jitter, whilst maintaining stable stepping?

Well if it's anything like the Mach3 Smoothstepper, machine performance usually isn't even relevant. And they do tend to run smoother and more torque due to dead-on accurate step timing.

I like the 7i92 because I'm only running an Ethernet connection to the computer, not a thick, length-limited parallel cable. And a laptop is just as good (5i25 requires a PCI slot). You could probably run it off a Raspberry Pi if you thought you had a reason.

Yep, 7i92 is a bit "bleeding edge" but I got the hang of it. Basic movement is all there. I'm still stuck on how to link 2x gantry axes and the Modbus and wireless MPG link- but those have nothing to do with the 7i92 setup.

Smoothstepper is a buffered motion controller. The computer doesn't have to be realtime to run it.

Linuxcnc needs a realtime connection between the computer and hardware. The external interface hardware like mesa moves the stuff computers don't do well - high speed stepgen, pwmgen, encoder counting and such. You then don't need a base thread - only a servo thread. So 1 to 5khz or so. Latencies can be higher - approaching 100us or more. (mesa has some cool DPLL magic to make jitter have less effect)

sam

Thank you for the clarification. I might go for the 7i92, connected to my existing (parallel port) Controller.

Any thoughts on which .bit should I use for a generic (chinese Yoocnc 3040) controller?

Thanks.

Best thing is to compare your existing pinout (step and dir mainly) with available bit file pinouts

BTW here is a reversed (IO connectors swapped) G540 config for the 7I92

freeby.mesanet.com/7i92_g540x2RD.bit

Debian 9 (Stretch)

Mesa 7i92M FPGA

Download 7i92 firmware from Mesa Elect.

Write /hostmot2/7i92_C11Gx2D.bit

mesaflash --device 7i92 --addr 10.10.10.10 --readhmid
Verified write, ports and pins.

Desktop menu>Applications>CNC>Pncconf Wizard
Page 5 at Mesa Card 0. Configuration Page doesn't have a default 7i92 board and C11Gx2D firmware in populated menu.

freeby.mesanet.com/7i92step.zip
Extracted 7i92step.zip
Placed 7i92.ini and hm2-pidstepper.hal at /home/shawn/linuxcnc/configs

Desktop menu>CNC>LinuxCNC>LinuxCNC Cofiguration Selector Current: 7i92.ini
My Configurations (tree) 7i92 No details available.
Double left click mouse opens AXIS.

Revert Pncconf Wizard and page 5. How does 7i92 board and C11Gx2D firmare get in populated menu? That to configure ports and pins, accept component changes and proceed Wizard.