PWM on 18F4525 - Electronic Circuits Projects Diagrams Free

futz · 9th May 2008, 03:07 PM

I've been grinding through the 18F4525 datasheet PWM sections and, unless I'm mistaken (I probably am

), it looks to me like you have to have both PWMs running off the same timer. Therefore they have to have the same duty cycle. This just won't do it for me. I need two independant duty cycles.

Do I have to build my own PWM with a different timer for the second motor output?

I'll be working on this more tonight. Must go to work now.

blueroomelectronics · 9th May 2008, 03:12 PM

Same period, independant duty though. CCP1 CCP2

joseph@e-tech · 9th May 2008, 03:44 PM

Quote:

Originally Posted by blueroomelectronics

Same period, independant duty though. CCP1 CCP2

what do you mean sir?

blueroomelectronics · 9th May 2008, 03:47 PM

The two PWM outputs share a common clock (period) but have their own duty registers.

joseph@e-tech · 9th May 2008, 03:51 PM

they have the same period but they can have there own pulse width

futz · 9th May 2008, 07:54 PM

Quote:

Originally Posted by blueroomelectronics

Same period, independant duty though. CCP1 CCP2

But of course!

Both wheels PWMing independantly now. Should have this thing at least attempting to balance by tonight. Tomorrow or Sunday at the latest.

I didn't need independant PWM to get it balancing, but for steering later I do.

I think what was throwing me on the datasheet was part of the Enhanced PWM chapter. I should have never looked at it. It just confused me.

futz · 10th May 2008, 04:49 AM

I got the balancer attempting to balance itself. I think it might even work with accelerometer only. But it's going to need faster motors and/or bigger wheels. It can't begin to catch itself. It's doing all the right things. The accelerometer is sensing the slightest tilt and turning on the motors correctly, but the motors just aren't fast enough to catch and correct the tilt.

In a lot of balancing robot web-sites I see the guy mention switching to bigger wheels or faster motors. Now I know why.

Now I'm going to dig through all my motors and wheels and see what I can come up with for tomorrow.

9th May 2008, 03:07 PM	#1 (permalink)
futz Experienced Member Join Date: Sep 2007 Location: Vancouver, B.C. Posts: 900	PWM on 18F4525 I've been grinding through the 18F4525 datasheet PWM sections and, unless I'm mistaken (I probably am ), it looks to me like you have to have both PWMs running off the same timer. Therefore they have to have the same duty cycle. This just won't do it for me. I need two independant duty cycles. Do I have to build my own PWM with a different timer for the second motor output? I'll be working on this more tonight. Must go to work now. __________________ ========================= Futz's Microcontrollers & Robotics =========================

9th May 2008, 03:12 PM	#2 (permalink)
blueroomelectronics Experienced Member Join Date: Jan 2007 Location: Toronto, Canada Posts: 4,123 Blog Entries: 1	Same period, independant duty though. CCP1 CCP2 __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

9th May 2008, 03:47 PM	#4 (permalink)
blueroomelectronics Experienced Member Join Date: Jan 2007 Location: Toronto, Canada Posts: 4,123 Blog Entries: 1	The two PWM outputs share a common clock (period) but have their own duty registers. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com

10th May 2008, 04:49 AM	#7 (permalink)
futz Experienced Member Join Date: Sep 2007 Location: Vancouver, B.C. Posts: 900	I got the balancer attempting to balance itself. I think it might even work with accelerometer only. But it's going to need faster motors and/or bigger wheels. It can't begin to catch itself. It's doing all the right things. The accelerometer is sensing the slightest tilt and turning on the motors correctly, but the motors just aren't fast enough to catch and correct the tilt. In a lot of balancing robot web-sites I see the guy mention switching to bigger wheels or faster motors. Now I know why. Now I'm going to dig through all my motors and wheels and see what I can come up with for tomorrow. __________________ ========================= Futz's Microcontrollers & Robotics =========================

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9th May 2008, 03:51 PM	#5 (permalink)
joseph@e-tech New Member Join Date: Apr 2008 Location: Balanga City,Philippines Posts: 5	they have the same period but they can have there own pulse width

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