Physical Feed override knob

Hi All,

So this might be a topic that has being ask (to) many times in some different ways.
I am a linuxcnc beginner and learning more and more how to adjust etc.

As a daily toolmaker, i am used to the Heidenhain TNC 620 and older.
For the feed&speed override knob, its uses a potentiometer (like) knob. No clicks and has a physical 0 and end. It can not do a full turn.

I would like to use a potentiometer (4k7 is what i have on stock now).
I'm using a Mesa 7i76e board.

How could i set this up?

It might be an idea to say if the pot is a log or lin type.

If you use gmoccapy you can use an external value. And your 7i76e has analog inputs. So you have what you need. Try to understand the gmoccapy document. In chapter 5.2 Norbert describes the details.
linuxcnc.org/docs/devel/html/gui/gmoccapy.html
I have it running with 7i73 inputs plus 7i76e. Very nice. Just learn to use halshow and read the analog value ( if i'm not wrong it is scaled up to 33v) and use a MULT2 to adjust the value for the gmoccapy pin.....
Sorry, before you ask, my config is quite complex and would distract you only. But I belive there is a good one in the examples.
Good luck.

Thanks! This might take me some where.
Yes, i use Gmoccapy.

So i should set it up in my hal file like this:

gmoccapy.feed.feed-override.direct-value => hm2_7i76e.0.7i76.0.0.input-** (pins on one of the inputs of TB5 or TB6.

The 7I76e analog input pins are named

hm2_7i76e.0.7i76.0.0.analogin0
hm2_7i76e.0.7i76.0.0.analogin1
hm2_7i76e.0.7i76.0.0.analogin2
hm2_7i76e.0.7i76.0.0.analogin3

You need to set the sserial mode to 1 or 2 for these pins to be available

Thanks!

That last one i don't understand, and don't no how to do that.

Erikcnc wrote:

Thanks!

That last one i don't understand, and don't no how to do that.

The instructions for most of the low level hardware setup for Mesa cards is
in the hostmot2 manual page

man hostmot2 (in the config modparam section)

For the 7I76e

sserial_port_0=20xxxxxx added to the configuration string of the hm2_eth driver in your hal or ini file
will set the mode of the field I/O section of the 7I76E to mode 2

Clive wrote:

It might be an idea to say if the pot is a log or lin type.

oh! the potentiometer is a lineaire type!

allright, i got the potentiometer working on the mesa 7i76e.
if i go to halshow and look at the pin in hm2_7i76e and select analogin0 i see its reading values from 0 to almoste 24.

gmoccapy.feed.feed-override.direct-value does not change in halshow.


I changed sserial_port_0=00xxxxxx to sserial_port_0=20xxxxxx.

do i have to enable it with gmoccapy.feed.feed-override.analog-enable.
and how?

manny thanks for helping!

To get a higher reading (and more resolution), you should connect the potentiometer to field power (12 or 24VDC)