7i96 non S PWM on an output possible?

  So I have a 7i96 non S version and I would like to use one of the general outputs 0-5 to send a pwm signal
to a dc to dc SSR capable of controlling 40 amps. The quick back ground is I am getting information together
for installing LinuxCNC on my 5 axis foam cutter and need a pwm for controlling duty cycle for the hot wire bow's
temperature. The reason for using the older 7i96 is because I have 2 in my inventory. So is it possible and if
so how much of a pain is it to do?

The SSR outputs on the 7I96 or 7I96S are relatively slow so
probably best driven by software PWM (the pwmgen component)
Your  40A SSR may also be fairly slow.

At an update rate of 1 KHz its probably best to use the PDM mode
(PWM frequency set to 0) but a low PWM frequency (like 20 Hz with dither
enabled) may also work well.

If you need a high speed PWM, you could use a configuration with
PWM on the P1 expansion connector (7i96_5abob_d.bit for example)

Thanks for the reply PCW. I highly doubt I will need a high speed pwm. I am just controlling
a resistive load. LOL. What kind of frequency can one of the outputs drive?

The 7I96/7I96S SSR outputs are good to a couple KHz
but the software PWM will be limited by the 1 KHz servo
thread rate. As I said either PDM or say a 20Hz PWM
frequency should be fine for a hot wire.

OK, Now I am in very uncharted waters. What is PDM? Is the PDM stuff setup in PNConf, or with HAL? Is there
a section in the LinuxCNC manual about it and if so what section would you recommend I check through? Sorry to
be a pest PCW but, I don't know, what I don't know.
 

If your 40 A SSR is slow, it's probably better to start with PWM:
something like

loadrt pwmgen output_type=0
addf pwmgen.update servo-thread
addf pwmgen.make-pulses servo-thread
setp pwmgen.0.dither-pwm true
setp pwmgen.0.pwm-freq 20
setp pwmgen.0.scale 100

net heat-on pwmgen.0.enable
net how-hot pwmgen.0.value # 0 to 100%
net pwm  pwmgen.0.pwm  hm2_7i96.0.ssr.00.out-05


man pwmgen for pwmgen usage

Thanks PCW. looks like I have some reading and experimenting to do.

Those hal commands should work as-is
as long as you know what needs to connect
to heat-on and how-hot (maybe those could be replaced
by spindle enable and spindle speed)

On many of the Arduino based stuff they usually repurpose the spindle output for hot wire control.

what is the difference between the 2 lines  below?
net spindle-enable  =>  [HMOT](CARD0).SSR.00.OUT-05
net spindle-enable  =>  hm2_7i96.0.ssr.00.out-05

 I just tested both and both do the exact same thing so why although different do they both work?
I am still very much a noob when it comes to code so seeing both work and yet be different has me
scratching my head.