I have managed to read the initial serial data which defines the absolute
position of an axis. The A and B channels of the absolute encoder are taken
to the 7i33 on P2 of a MESA 5i23 as usual, The A channel which also carries
the serial data when enabled initially, is also taken to a GPIO input on P4
of a Mesa 5i23, which also has a 7i37 on P3 for other purposes.

A component running at a thread rate matching the baud rate of 9600 of the
serial data catches the serial data and interprets it to give the number of
full revs Nf of the encoder from its set ref point. After the eight bytes of
serial data is received, the encoder also sends out a number of A/B pulses
providing the increment count C for a fraction of a rev. This count is given
by the 5i23 encoder count. The total number of revs from ref point is then
Nt = Nf + C/400, for 400 counts per rev.

With Nt and the joint scale of degrees/encoder-turn I have the joint
position as degrees from its absolute ref point.

I now have to use the value to set the absolute position for the joint, but
have not found the best way to do this in Linuxcnc yet.
Any ideas from the experienced Linuxcnc users on this?

Rudy


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