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peter.rebeiro
Joined: 12 Jan 2016
Posts: 2
Location: mumbai
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| CCP1 Half bridge waveforms question |
 Posted: Wed Jan 13, 2016 12:33 am |
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Dear all I'm new in this programing.
In my ccp1 half bridge programing I'm getting in my SCOPE waveform result like this:
P1A: ___|--|___
P1B: ----|__|----
but I actually want it like this:
P1A: ____|--|___
P1B: |--|_____|--|___
My humble request is that please help me some one.
my Code is:
| Code: |
void main()
{
long value,value1;
while( 1 )
//if (INPUT(PIN_B0)==0)
{
setup_ccp1(CCP_PWM_L_H | CCP_PWM_HALF_BRIDGE);
setup_timer_2(T2_DIV_BY_4,99,1);
setup_adc_ports(AN0_TO_AN1);
setup_adc(ADC_CLOCK_INTERNAL);
set_adc_channel(1);
value=read_adc();
value1=read_adc();
set_pwm1_duty(value);
}
}
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Ttelmah
Joined: 11 Mar 2010
Posts: 19504
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| Posted: Wed Jan 13, 2016 2:11 am |
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WHAT PIC....
Makes a huge difference to the options available. |
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peter.rebeiro
Joined: 12 Jan 2016
Posts: 2
Location: mumbai
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| CCP1 Half bridge waveforms question |
| Posted: Wed Jan 13, 2016 5:51 am |
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Thank you for your attention
The uc ic PIC 18F4520 |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19504
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| Posted: Wed Jan 13, 2016 8:12 am |
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Look at figure 16-2 'PWM output relationships'.
The key point is that the gap between the falling edge of P1A, and the rising edge of P1B, is the bit marked there as 'delay'. This is the 'dead band delay', designed to stop there being a conflict if it takes longer to turn a driver off, than on. So you need to increase this.
This unfortunately is one of those awfully documented things. It has been discussed here before. This is actually the optional parameter in the setup_ccp function.
So:
| Code: |
setup_ccp1(CCP_PWM_L_H | CCP_PWM_HALF_BRIDGE, 5);
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Sets the dead band delay to 5. Try increasing and decreasing the value and you will see the gap between the edges change. |
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