PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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 Posted: Sat May 05, 2007 1:00 am |
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With respect pin to C5, it's behaving correctly for the Full Bridge mode.
It's the P1A pin in that mode. According to Figure 11-6 in the 16F685
data sheet, pin C5 will be either a constant high or a constant low,
depending upon whether you're going in forward or reverse.
So pin C5 is OK.
There is a note in Section 11.5 of the data sheet (PWM Enhanced mode).
It says:
| Quote: | | The TRIS register value for each PWM output must be configured appropriately. |
However, the ASM code generated by the compiler doesn't do this.
It only sets pin C5 as a low-level output pin. It leaves the other pins
(C2, C3, C4) in the default state, which is as input pins.
Here's something you could try. Add a line of code after each
setup_ccp1() function, to manually force pins C2-C5 to be outputs.
Add the lines shown in bold below.
| Quote: |
#include <16F685.h>
#fuses XT,NOWDT,BROWNOUT,PUT
#use delay (clock=4000000)
//=================================
void main()
{
// Setup the ECCP for PWM in full bridge mode.
setup_ccp1(CCP_PWM_FULL_BRIDGE | CCP_PWM_H_H);
set_tris_c(0xC3); // Set pins C2-C5 as outputs
setup_timer_2(T2_DIV_BY_1, 255, 1);
set_pwm1_duty(100);
// Switch the H-Bridge outputs between forward
// and reverse every 5 seconds.
while(1)
{
// Run forward for 5 seconds.
setup_ccp1(CCP_PWM_FULL_BRIDGE | CCP_PWM_H_H);
set_tris_c(0xC3); // Set pins C2-C5 as outputs
delay_ms(5000);
// Run in reverse for 5 seconds.
setup_ccp1(CCP_PWM_FULL_BRIDGE_REV | CCP_PWM_H_H);
set_tris_c(0xC3); // Set pins C2-C5 as outputs
delay_ms(5000);
}
} |
Then compile it and program it. Then when it's running, look at pin C2
in forward mode, and pin C4 in reverse mode. You should see PWM
pulses on them. |
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