7i76E one PWM needed

Hello,

I have a 7i76E card setup and running. Now I need a PWM generator to control a L298 H-bridge.
I've already install the Xilinx software and I'm able to compile bit files. Which PIN file is supplied with the 7i76e file when it's shipped?
Is it possible to add one PWM generator and have PWM functionality on one of the GPIO pins? How should I proceed?

Kind regards,

Chris

PIN_7i76x1D_51.vhd is the pin file used for creating the default 7I76E config
You would need to add the PWM to one of the expansion port pins (or steal a step/ dir pin if you dont need all 5)

I only use three stepgen generators so I can use the fourth for PWM. I'll give it a try this evening.

I've got it working! Thanks for your help!

Regards Chris

That's great. Its a really big help when people can make their own custom bitfiles

(I realize not everyone can or wants to do this)

Hi,

I ran into a little annoying issue. When I close Linuxcnc or turn off the PC the PWM value will go to 100% (5V). How can I change this behaviour so it will be 0% (0V)?

Chose the other differential pair output (so its 0V when the 7I76E is idle) and invert the PWM output in HAL

Must have been too late Don't know why I forgot it's differential.. Thanks!!!

Okay this works, but there is some sort of glitch of a few 100ms during startup of Linuxcnc. The negative pin is low when linuxcnc is not running which is good. At startup of linuxcnc the pin will go high and stay high until the invert command is executed.

So I'm not sure it can be solved in linuxcnc. Is it possible to change the FPGA code so when I use the positive pin PWM will stay 0 if Linuxcnc is closed?

Yes, you would probably have to change the FPGA code to get a glitch free startup
You will always need to use the negative output as this is the only output that will stay at 0 when linuxcnc is not running

What is required is to make the FPGA PWM output active low. To do this as a hack you would
change ( in pwmpdmgenh.vhd )

to