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lsteele
Joined: 02 Jan 2007 Posts: 18
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pwm and interrupt on change on 18f2431 |
Posted: Tue Feb 19, 2008 1:36 pm |
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Hello,
I'm using an 18f2431 and I want to be able to have two pwm outputs and also independently use two port b pins as inputs using the interrupt on change feature.
I was intending to use the power pwm feature on the chip for the two pwm outputs, but it looks like I have to give up two pins per pwm channel, which seems wasteful. As I've understood it each channel is allocated to two adjacent port b outputs, so pwm0 is on b0 and b1, pwm 1 on b2 & b3, and pwm 3 on b4 and b5. So I was thinking I could use pwm channel 3 leaving pins b0-b3 free. But I'm having a great deal of difficulty getting this to work and can't work out a configuration that'll give me the results I want. Is what I've described possible?
Any help is really appreciated as I'm finding the datasheet somewhat cryptic!
Thanks in advance. If I need to provide more information please let me know.
Luke |
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PCM programmer
Joined: 06 Sep 2003 Posts: 21708
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Posted: Tue Feb 19, 2008 6:21 pm |
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Quote: |
So I was thinking I could use pwm channel 3 leaving pins b0-b3 free |
PWM channel 3 is not implemented in 18F2431. Only channels 0, 1, 2
are available. So you must mean you want to use Channel 2.
The PWM pin assignment options are listed in the 18F2431 data sheet.
Quote: |
Ch. 2
RB5 -- PWM4
RB4 -- PWM5
Ch. 1
RB3 -- PWM3
RB2 -- PWM2
Ch. 0
RB1 -- PWM1
RB0 -- PWM0
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The available combinations are listed below. It doesn't show a setting
to select PWM channel 2 only.
Quote: |
REGISTER 17-3: PWMCON0: PWM CONTROL REGISTER 0
bits 6-4 PWMEN2:PWMEN0: PWM Module Enable bits
111 =All odd PWM I/O pins enabled for PWM output.
110 =PWM1, PWM3 pins enabled for PWM output.
101 =All PWM I/O pins enabled for PWM output.
100 =PWM0,PWM1,PWM2,PWM3,PWM4 and PWM5 pins enabled for PWM output.
011 =PWM0, PWM1, PWM2 and PWM3 I/O pins enabled for PWM output.
010 =PWM0 and PWM1 pins enabled for PWM output.
001 =PWM1 pin is enabled for PWM output.
000 =PWM module disabled. All PWM I/O pins are general purpose I/O. |
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