Posted on May 17, 2011 at 13:24What 'smart' said is right, you don't need to re-initialize the output channel... this is how I would do it.
Code:
void InitTheWholeTimer()
{
//Enable clocks to the desired modules
{
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,
ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC | RCC_APB2Periph_AFIO,
ENABLE);
}
//Initialise the GPIO
{
GPIO_InitTypeDef stGPIOInit;
stGPIOInit.GPIO_Mode = GPIO_Mode_AF_PP;
stGPIOInit.GPIO_Pin = GPIO_Pin_6;
stGPIOInit.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOC,
&stGPIOInit);
}
//Pin remap
{
GPIO_PinRemapConfig(GPIO_FullRemap_TIM3,
ENABLE);
//I don't really trust the above function. So... if it still don't work
/*AFIO->MAPR |= AFIO_MAPR_TIM3_REMAP_FULLREMAP;*/
}
//Initialise time-base
//Lets say we need a 150Khz square wave with 40% duty cycle
//My APB1 is running at 36MHz
//Hence value for period should be
// period = ((2 * APB1) / (prescaler * frequency) - 1)
// = ((2 * 36,000,000) / (prescaler * 150,000) - 1)
//
//I would divide the timer clock by 32 without having to
//sacrifice the precision in duty cycle. Hence
// period = (72,000,000 / (32 * 150,000) - 1)
// = (15 - 1) = 14
//
//Theoretically, lower the clock, lesser the power consumption!
{
TIM_TimeBaseInitTypeDef stTimebase;
stTimebase.TIM_ClockDivision = TIM_CKD_DIV1; //0
stTimebase.TIM_CounterMode = TIM_CounterMode_Up;
stTimebase.TIM_Period = 14;
stTimebase.TIM_Prescaler = 31;
TIM_TimeBaseInit(TIM3,
&stTimebase);
}
//Initialise output channel
{
TIM_OCInitTypeDef stOCInit;
stOCInit.TIM_OCMode = TIM_OCMode_PWM1;
stOCInit.TIM_OCPolarity = TIM_OCPolarity_High;
stOCInit.TIM_OutputState = ENABLE;
stOCInit.TIM_Pulse = 6; //15 * 40 / 100
TIM_OC1Init(TIM3,
&stOCInit);
}
//Start the timer (and get the waveform)
TIM_Cmd(TIM3,
ENABLE);
}
I am not quite sure about the preload configuration, but that may be the one causing you trouble!
