Posted on July 21, 2015 at 13:07Hi
I have read through a couple of posts that clive1 has made regarding phase shifts in toggle mode. I need 120º shifts between each of the 3 PWM channels. I get 120º shift between channel 1 and 2, but anything more than 30º shift between channel 2 and 3 the PWM flatlines.
The code I use:
TimerPeriod = (SystemCoreClock / 22500);
Channel1Pulse = (TimerPeriod / 6);
Channel2Pulse = (TimerPeriod / 6) + ((TimerPeriod * 2) / 3);
Channel3Pulse = (TimerPeriod / 6) + ((TimerPeriod * 3) / 3);
/* Time Base configuration */
TIM_TimeBaseStructure.TIM_Prescaler = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_Period = TimerPeriod - 1;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);
/* Channel 1, 2,3 and 4 Configuration in Toggle mode */
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Reset;
TIM_OCInitStructure.TIM_Pulse = Channel1Pulse;
TIM_OC1Init(TIM1, &TIM_OCInitStructure);
TIM_OCInitStructure.TIM_Pulse = Channel2Pulse;
TIM_OC2Init(TIM1, &TIM_OCInitStructure);
TIM_OCInitStructure.TIM_Pulse = Channel3Pulse;
TIM_OC3Init(TIM1, &TIM_OCInitStructure);
Images to illustrate what happens:
Shift of 30º -
https://drive.google.com/open?id=0B9k0m1UMqSODdEdLYnpERWpLeEk Shift of anything more -
https://drive.google.com/open?id=0B9k0m1UMqSODc0NvZUxuVDV3b0U
