MikroBasic to PBP Pro: Boost mode SMPS

[jmgelba]

Ok, I understand everything up until this:

ccp1con=$0C

The pwm is already turned on as per the CCP1CON line.

[jmgelba]

Frustrated. Not sure what I am missing now. The CCP1 pin is always high, LED flashes correctly.

DEFINE OSC 48
DEFINE ADC_BITS 10
DEFINE ADC_CLOCK 3
DEFINE ADC_SAMPLEUS 50
DEFINE CCP1_REG PORTC
DEFINE CCP1_BIT 2   


final_period var byte
final_duty var byte
high_duty var byte
low_duty var byte


ADCON1 = 00001011
ADCON2 = 00000011


TRISA = 00001111
TRISB = 01110000
TRISC = 00000000
CMCON = 7


CCP1CON = 00111100
PR2 = 44
high_duty=(final_duty>>2)        'high 6 bits in CCPR1L
      low_duty=(final_duty<<6)         'low two bits for CCP1CON
      low_duty=(low_duty>>2)           'shift back to CCP1CON<5:4>
      low_duty.3=1                     'PWM configuration bit
      low_duty.2=1                     'PWM configuration bit
CCPR1L=high_duty
CCP1CON = $0C
T2CON = 4


main:
PORTC.0 = 1
pause 500
PORTC.0 = 0
Pause 500
goto main

[jmgelba]

Figured it out. Helps to have a value for final_duty to load!
final_duty = 136

This gives me exactly what my calculations showed. 3.76uS at 75% duty cycle. 265.90KHz

Splendid!!

[Ioannis]

Sorry I was not online earlier. Which PIC are you using?

Ioannis

[jmgelba]

I am using a 18F2550.

I seem to have it working at the moment however it is not very smooth.

When the on/off button is pressed I need to sweep from 0% duty cycle up to the set limit in 1 second. I can see this happening by writing the incremental counter results to EEPROM and reading them later, however, the duty cycle does not increase for every +1 increase of the duty cycle byte. I assume this is a resolution issue due to running at 48MHz?

I really need to smooth that out and give a very nice gradual increase in light over time.

Also, what is a good way to have the program wait for a pin to go high?

Currently I am using:

waitforon:
If PORTB.7 = 1 then 'on/off button pulled high = on
gosub rampup 'increments final_duty and outputs value to CCP1
endif
PORTC.0 = 1 'flash heartbeat LED
pause 100
PORTC.0 = 0
pause 100
If final_duty = limit then 'if returned to waitforon from rampup, then final_duty is at set limit, so move on to main program
goto main
endif
goto waitforon


Sometimes this will not move to rampup: or move on to main: but the heartbeat LED will always flash correctly.

[jmgelba]

This is the rampup subroutine.

rampup:
For final_duty = 1 to limit
delay = 1000 / limit
pause delay
CCP1CON = %00111100
PR2 = 44
high_duty=(final_duty>>2) 'high 6 bits in CCPR1L
low_duty=(final_duty<<6) 'low two bits for CCP1CON
low_duty=(low_duty>>2) 'shift back to CCP1CON<5:4>
low_duty.3=1 'PWM configuration bit
low_duty.2=1 'PWM configuration bit
CCPR1L=high_duty
CCP1CON = $0C
T2CON = 4
Next final_duty


return

[jmgelba]

Alright, last question of the day, I promise!

This is the main loop code. It works fine holding the current limit by pulse skipping. The current limit is set by comparing the ADC reading to a value stored in fb, 205 in this case, or about 175mA for this application.
The problem comes when the down button is pressed. Instead of lowering fb by 1 it goes to 100% duty cycle, and my current goes as high as the current limit is set on my bench power supply and I have to yank the power.
I thought by lowering, or raising the value in fb, I would be able to control the current limit? What is going on?

main:
If PORTB.6 = 1 then
fb = fb - 1
If fb => 205 then
fb = fb
endif
endif
adcin 1, temp
If temp > fb then
final_duty = final_duty - 1
IF final_duty = 0 then
final_duty = final_duty
endif
endif
If temp < fb Then
final_duty = final_duty + 1
If final_duty = 44 then 
final_duty = final_duty
endif
endif




CCP1CON = %00111100
PR2 = 44
high_duty=(final_duty>>2)        'high 6 bits in CCPR1L
      low_duty=(final_duty<<6)         'low two bits for CCP1CON
      low_duty=(low_duty>>2)           'shift back to CCP1CON<5:4>
      low_duty.3=1                     'PWM configuration bit
      low_duty.2=1                     'PWM configuration bit
CCPR1L=high_duty
CCP1CON = $0C
T2CON = 4


goto main