7i76E one PWM needed
10 Jan 2016 12:57 #68155
by sirhc
7i76E one PWM needed was created by sirhc
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
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
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10 Jan 2016 16:16 - 10 Jan 2016 16:17 #68157
by PCW
Replied by PCW on topic 7i76E one PWM needed
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)
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)
Last edit: 10 Jan 2016 16:17 by PCW.
The following user(s) said Thank You: sirhc
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10 Jan 2016 16:38 #68158
by sirhc
Replied by sirhc on topic 7i76E one PWM needed
I only use three stepgen generators so I can use the fourth for PWM. I'll give it a try this evening.
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11 Jan 2016 21:52 #68200
by sirhc
Replied by sirhc on topic 7i76E one PWM needed
I've got it working! Thanks for your help!
Regards Chris
Regards Chris
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11 Jan 2016 23:26 - 11 Jan 2016 23:26 #68209
by PCW
Replied by PCW on topic 7i76E one PWM needed
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)
(I realize not everyone can or wants to do this)
Last edit: 11 Jan 2016 23:26 by PCW.
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23 Jan 2016 00:12 #68945
by sirhc
Replied by sirhc on topic 7i76E one PWM needed
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)?
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)?
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23 Jan 2016 01:27 #68948
by PCW
Replied by PCW on topic 7i76E one PWM needed
Chose the other differential pair output (so its 0V when the 7I76E is idle) and invert the PWM output in HAL
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23 Jan 2016 10:25 #68958
by sirhc
Replied by sirhc on topic 7i76E one PWM needed
Must have been too late
Don't know why I forgot it's differential.. Thanks!!!
![:silly: :silly:](/media/kunena/emoticons/silly.png)
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23 Jan 2016 14:49 #68968
by sirhc
Replied by sirhc on topic 7i76E one PWM needed
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?
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?
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23 Jan 2016 15:22 - 23 Jan 2016 15:23 #68969
by PCW
Replied by PCW on topic 7i76E one PWM needed
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
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 )
when "00" =>
pwmouta <= pwm; -- normal sign magnitude
pwmoutb <= dir;
when "01" =>
to
when "00" =>
pwmouta <= not pwm; -- normal sign magnitude
pwmoutb <= dir;
when "01" =>
Last edit: 23 Jan 2016 15:23 by PCW.
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