7I92 + generic 5axis BOB - X & B axis config help & 5th dir stepgen missing.

17 Jun 2022 21:06 #245352 by MrJRB

I've been configuring my machine via this guide and things have gone alright so far.
I'm using a 7i92M with a generic 5 axis BOB bought from here .

Through trial and error (to find which stepgen pin sets connect to each axis terminal set on the BOB) I've got the Y and Z axis moving.
I can't get the X moving unless I wire such to the A axis terminal set (whether configured as X or A).
Given I can't get the X and B axis terminals sending out any signals I can't really get this machine working other than for the basics, XYZ etc.

I'm using the G540x2 firmware PnCConf setting and therefore the last stepgen pin set is missing it's direction pin.
From the comparison below for the BOB you can see I/O pin 7 should be that last stepgen pin unlike with the G540 whereas the pin would be unused.

Here are some photos of the Mesa/IO config in PnCConf as well as mesaflash output.

The firmware I've wrote to the 7i92M is "7i92_5ABOBx2D.bit".

How would I go about using I/O port 7 as a stepgen in my current situation?
Can I manually change it from a GPIO to a stepgen pin in PnCConf or would I need to do things elsewhere?

This probably won't solve why both terminal sets aren't working but if I can have at least one working then I can at least get things functional for what I need (I don't have a B axis).
Albeit annoying given I may not have the wiring go to the exact labelled terminals intended.

Many thanks,


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17 Jun 2022 23:31 - 17 Jun 2022 23:32 #245358 by PCW
To use the 5th ( B ) axis on the 5ABOB you need to assign it to stepgen 8
(probably directly in the hal file since pncconf wont do this )

The pin assignments are:

X DB25 2.3 Stepgen 0
Y DB25 4,5 Stepgen 1
Z DB25 6,7 Stepgen 2
A DB25 8,9 Stepgen 3
B DB25 16,17 Stepgen 8

The last stepgen is set to 8 so the pin 17 can be used to control
the relay (by only enabling stepgens 0..3, so pins 16,17 revert to GPIO)
Last edit: 17 Jun 2022 23:32 by PCW.
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18 Jun 2022 23:06 - 18 Jun 2022 23:17 #245410 by MrJRB
Cheers, your explanation made me realise what I was doing wrong.

I hadn't considered the difference between the 5ABOB pin config and the PnCConf G540 I/O connector profiles (stepgen channel numbers wise) as well as the fact I was actually connected to physical I/O connector 1. (configured the profiles' stepgens identically hence why any axis worked at all).

Just needed to clear connector profile 2 and set it's B axis stepgen as the X (stepgen 4 being B for G540 but X for 5ABOB) as well as add a line of custom HAL for inverting the direction.

For anyone who is in the same situation I was, here's my profile configs as well as the custom HAL line:
(NOTE: E_stop setting likely wrong, am using my E-stop to just cut off power, thus it's not doing anything and is probably the wrong pin)
setp hm2_7i92.0.stepgen.04.direction.invert_output true

I don't need to use the B axis terminals now that I've got the actual X ones working but good to know I need to do such in HAL should I add a B axis in future.
Last edit: 18 Jun 2022 23:17 by MrJRB. Reason: Added note with regard to to E stop pin setting in photo, remove code formatting from last sentence.
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