PWM signals on MOD54415
Posted: Mon Apr 15, 2013 7:34 am
Hi,
For my application I need to generate three signals by means of the PWM outputs. One +/- 4 MHz clock signal, one +/- 8 MHz clock signal and a start pulse.
I have looked carefully at the NCF54418 reference manual and it seems relatively straightforward to get that done.
I have come up with the code below to do so but I must be missing something because I am not getting any sort of signal at all.
The code is definitely being executed because I do get to see both Development board LED's lighting up.
Any suggestions as to what I am doing wrong or overlooking ?
For my application I need to generate three signals by means of the PWM outputs. One +/- 4 MHz clock signal, one +/- 8 MHz clock signal and a start pulse.
I have looked carefully at the NCF54418 reference manual and it seems relatively straightforward to get that done.
I have come up with the code below to do so but I must be missing something because I am not getting any sort of signal at all.
The code is definitely being executed because I do get to see both Development board LED's lighting up.
Any suggestions as to what I am doing wrong or overlooking ?
Code: Select all
void InitPWMs (void)
{
LED1 = LED_ON;
sim1.gpio.par_sdhcl = 0x02; // set pin function to PWM for A0
sim1.gpio.par_sdhch = 0x88; // set pin functions to PWM for A1,A2
// configure PWM A0 to generate a 7.8125 Mhz clock signal (50% duty cycle)
sim1.mcpwm.sm[0].cr1 = 0x0404;
sim1.mcpwm.sm[0].cr2 = 0x2000;
sim1.mcpwm.sm[0].init = 0; // start counter value (reload)
sim1.mcpwm.sm[0].val[1] = 16; // end counter value Clock = 125 MHz, divide by 16 => 7.8125 MHz
sim1.mcpwm.sm[0].val[2] = 0; // PWM A ON counter value
sim1.mcpwm.sm[0].val[3] = 8; // PWM A OFF counter value
sim1.mcpwm.sm[0].ocr = 0;
sim1.mcpwm.sm[0].dismap=0xFFF0;
// configure PWM A1 to generate a 3.90625 Mhz clock signal (50% duty cycle)
sim1.mcpwm.sm[1].cr1 = 0x0404;
sim1.mcpwm.sm[1].cr2 = 0x2000;
sim1.mcpwm.sm[1].init = 0; // start counter value (reload)
sim1.mcpwm.sm[1].val[1] = 32; // end counter value Clock = 125 MHz, divide by 32 => 3.90625 MHz
sim1.mcpwm.sm[1].val[2] = 0; // PWM A ON counter value
sim1.mcpwm.sm[1].val[3] = 16; // PWM A OFF counter value
sim1.mcpwm.sm[1].ocr = 0;
sim1.mcpwm.sm[1].dismap=0xFFF0;
// configure PWM A2 to generate a start pulse signal (base clock = 7,8125 MHz)
sim1.mcpwm.sm[2].cr1 = 0x0404;
sim1.mcpwm.sm[2].cr2 = 0x2000;
sim1.mcpwm.sm[2].init = 0; // start counter value (reload)
sim1.mcpwm.sm[2].val[1] = 20000; // end counter value = 1250 periods of 7.8125 MHz
sim1.mcpwm.sm[2].val[2] = 1; // PWM A ON counter value
sim1.mcpwm.sm[2].val[3] = 2; // PWM A OFF counter value
sim1.mcpwm.sm[2].ocr = 0;
sim1.mcpwm.sm[2].dismap=0xFFF0;
sim1.mcpwm.outen = 0x0700; // enable PWM outputs A0,A1,A2
sim1.mcpwm.mcr = 0x0007; // set LDOK for PWM outputs A0, A1, A2
sim1.mcpwm.mcr = 0x0700; // start PWM clocks (RUN flags)
LED2 = LED_ON;
}