On 12/12/2020 08:12 PM, Matthew Herd wrote:
Jon, I have two USC boards on the same parallel port. I think there is a bit of a
clarity issue in the documentation here:
http://www.linuxcnc.org/docs/html/drivers/pico-ppmc.html
<http://www.linuxcnc.org/docs/html/drivers/pico-ppmc.html>. The loadrt command
references parallel port addresses. Then the extradac=0xnn explanation indicates
that a second board on the same parallel port should be referenced as 0x02.
Nope. The ppmc.n. references the parallel port, starting at
0. Then, functions on the various devices are just
enumerated from 0. So, if you have two PWM controllers, they
will enumerate (normally)
as ppmc.0.pwm.00 through ppmc.0.pwm.03 and the second board
will be ppmc.0.pwm.04 through pwm.07. The first board's
encoders will be encoder.00 through encoder.03 and the 2nd
board will be encoder.04 through encoder.07.
Since multiple boards exchange sync signals on the parallel
cable, it is best to have all boards on the same parallel
port. I'm guessing what you have done is to assign the I/O
port address of your parallel port to the 3rd possible
parport in the loadrt command line. I guess there's no
reason that this is in any way "wrong", it just surprised
me, as I've never used the additional parallel port "slots"
on the command line.
Secondly, I had a few questions about your -1/+1 multiplication for the spindle
speed. I just want to confirm that if I command an M3 S-1000 (assuming a plain
configuration as shown in my current config), the spindle will run in reverse
without any other input.
No, I don't think that will work, but it might. generally,
you use M03 for "forward" spindle, and M04 for "reverse".
The way this works is the spindle speed is fed to the
spindle DAC as a positive number (absolute value), and the
direction is commanded by the SSR1 (forward) or SSR2 (reverse).
spindle.0.forward and spindle.0.reverse are brought out from
inside LinuxCNC when the spindle speed is non-zero in that
direction. univpwm_io.hal just routes those to the first two
solid state relays.
Jon
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