16 bit PWM using CCP1
I am trying to do 16 bit PWM as per Tip#10 16 bit Resolution PWM page 40 (3-10) Microchip Tips 'n Tricks
Basically when TM1 value equals the CCP1 (PWM duty) setting the CCP1 interrupt sets PORTC.2 low (works OK).
When the free running TM1 interrupts it is supposed to set PORTC.2 high (doesn't).
As a test CCP1 can be configured to toggle (this works OK as see in ISIS) but if configured
to set low for PWM the pin cannot be set high again even though CCP1 int is cleared.
The following code tries to set pin high in TM1 interrupt.
Norm
Code:'FL PIC18F4520 ; @ __CONFIG _CONFIG1H, _OSC_XT_1H @ __CONFIG _CONFIG1H, _OSC_HSPLL_1H @ __CONFIG _CONFIG2L, _BOREN_ON_2L @ __CONFIG _CONFIG2H, _WDT_ON_2H @ __CONFIG _CONFIG3H, _MCLRE_ON_3H & _PBADEN_OFF_3H @ __CONFIG _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L DEFINE OSC 40 Clear sSEROUT_PIN VAR PORTA.2 sBAUD CON 16416 '16416 = 19200 BAUD wsave VAR BYTE bankA system ' Saves W ssave VAR BYTE bankA system ' Saves STATUS yTEMP VAR Byte wDUTY VAR Word wDUTY = 32768 '32768 = 50% DUTY PWM '******************** '16 BIT CCP1 PWM Input PORTC.2 ' Disable the HPWM output while things are being setup RCON.7 = 0 ' 0 DISABLES PRIORITY LEVELS ON INTERRUPTS (16F COMPATABILITY) T1CON = %10110000 ' Turn off Timer1 with a Prescaler value of 1:8 PIE1 = %00000101 ' enable CCP1, TMR1 overflow interrupt INTCON = %11000000 ' enable global and peripheral interrupts Output PORTC.2 ' Set PORTC.2 (CCP1) to output ' CCP1CON = %00000010 'TOGGLE PORTC.2 ON MATCH TM1 WITH DUTY ********** OK ************ CCP1CON = %00001001 'LOW PORTC.2 ON MATCH TM1 WITH DUTY ?????????? NOT OK ??????????????? T3CON = %00000000 ' CCPR1L = wDUTY.LOWBYTE CCPR1H = wDUTY.HighByte CCPR1L = wDUTY.LowByte DEFINE INTHAND myint Goto START 'Jump over the subroutines '**** ASSEMBLY INTURRUPT ROUTINE **** Asm myint ;KEEP LEFT ; Save the state of critical registers movwf wsave ; Save W swapf STATUS, W ; Swap STATUS To W (swap avoids changing STATUS) clrf STATUS ; Clear STATUS movwf ssave ; Save swapped STATUS EndAsm ' yTEMP = yTEMP +1 ' SerOut2 sSEROUT_PIN,sBAUD,["INT ",DEC yTEMP,13] PIR1.2 = 0 ' CLEAR THE CCP1 INT FLAG High PORTC.2 '???????????????? DOES NOT SET HIGH ????????????????? Asm bcf PIR1, 0 ; Clear interrupt flag swapf ssave, W ; Retrieve the swapped STATUS value (swap To avoid changing STATUS) movwf STATUS ; Restore it To STATUS swapf wsave, F ; Swap the stored W value swapf wsave, W ; Restore it To W (swap To avoid changing STATUS) retfie ; Return from interrupt EndAsm '**** END ASSEMBLY INTURRUPT ROUTINE **** '*********************************************** '*********************************************** START: PAUSE 800 SerOut2 sSEROUT_PIN,sBAUD,["START",13] T1CON.0 = 1 'TMR1 ON MAIN: yTEMP = yTEMP +1 SerOut2 sSEROUT_PIN,sBAUD,["LOOP ",Dec yTEMP,13] PAUSE 500 Goto MAIN End
Originally Posted by Darrel Taylor
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