Posted on May 17, 2011 at 12:18I am using the Keil tools and REV B silicon of STM32F103RB.
In attempting to set up the TIM1 peripheral in output compare mode to generate 4 pulses, I had to enable the remapping of the USART1 peripheral before the output would work on TIM1 CH 2. (PA9)
GPIO_PinRemapConfig(GPIO_Remap_USART1, ENABLE);
Prior to this, I had not set up the USART1 peripheral at all, as this USART is not used. This is how I configured the GPIO for port A:
// Configure Port A Alternate Function push-pull outputs
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1 | GPIO_Pin_2 |
GPIO_Pin_7 | GPIO_Pin_8 | GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_11;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOA, &GPIO_InitStructure);
It seems like the USART1 is ''connected'' to PA9 until I set the remap bit. Then it is connected to the TIM1 AF. Is there another way to do this so that I do not have to remap the USART1? I don't want to use the USART at all, and I want to be able to use PB6 & PB7 for I2C in the future.
Another problem I am having with this is that for the 4 output compares on TIM1, as soon as I enable the output compare for channel 2 (even before starting the timer), the output compare channel 2 goes high. The rest of the channels behave as intended, going high only after the output compare fires. I think this might be related to the problem mentioned above? I am using TIM1_OCMode_Active and TIM1_OCPolarity_High.
This is the initialization code for the timer timebase:
{
TIM1_TimeBaseInitTypeDef TIM1_TimeBaseStructure;
/* Time base configuration */
TIM1_TimeBaseStructure.TIM1_Period = 0xFFFF;
TIM1_TimeBaseStructure.TIM1_Prescaler = 8;
TIM1_TimeBaseStructure.TIM1_ClockDivision = 0x0;
TIM1_TimeBaseStructure.TIM1_CounterMode = TIM1_CounterMode_Up;
TIM1_TimeBaseInit(&TIM1_TimeBaseStructure);
}
The following code gets called at a periodic rate to set up the timer output compares:
{
TIM1_OCInitTypeDef TIM1_OCInitStructure;
TIM_Servos.Tim1_Done=0;
// Make sure the timer is disabled
TIM1_Cmd(DISABLE);
// Disable each output compare channel
TIM1_CCxCmd(TIM1_Channel_1,DISABLE);
TIM1_CCxCmd(TIM1_Channel_2,DISABLE);
TIM1_CCxCmd(TIM1_Channel_3,DISABLE);
TIM1_CCxCmd(TIM1_Channel_4,DISABLE);
// Reset the timer to zero
TIM1->CNT = 0x0000;
/* Output Compare Toggle Mode configuration: Channel1 */
TIM1_OCInitStructure.TIM1_OCMode = TIM1_OCMode_Active; // This says to set the pin to active on match
TIM1_OCInitStructure.TIM1_OCPolarity = TIM1_OCPolarity_High; // This sets the active state to high
TIM1_OCInitStructure.TIM1_Pulse = 0x0FFF;
TIM1_OC1Init(&TIM1_OCInitStructure); // Initialize OCMP1
TIM1_OCInitStructure.TIM1_Pulse = 0x0FFF;
TIM1_OC2Init(&TIM1_OCInitStructure);
TIM1_OCInitStructure.TIM1_Pulse = 0x0FFF;
TIM1_OC3Init(&TIM1_OCInitStructure);
TIM1_OCInitStructure.TIM1_Pulse = 0x0FFF;
TIM1_OC4Init(&TIM1_OCInitStructure);
// Force all of the output compare lines to low
GPIO_WriteBit (GPIOA, GPIO_Pin_9,Bit_RESET);
GPIO_WriteBit (GPIOA, GPIO_Pin_10,Bit_RESET);
GPIO_WriteBit (GPIOA, GPIO_Pin_11,Bit_RESET);
GPIO_WriteBit (GPIOA, GPIO_Pin_12,Bit_RESET);
// Enable each output compare channel
TIM1_CCxCmd(TIM1_Channel_1,ENABLE);
TIM1_CCxCmd(TIM1_Channel_2,ENABLE); // <-- When this line runs, the output compare 2 line (PA9) goes high immediately. The other channels do not behave tis way.
TIM1_CCxCmd(TIM1_Channel_3,ENABLE);
TIM1_CCxCmd(TIM1_Channel_4,ENABLE);
// Enable the capture/compare interrupts for each channel
TIM1_ITConfig(TIM1_IT_CC1 | TIM1_IT_CC2 | TIM1_IT_CC3 | TIM1_IT_CC4, ENABLE);
// Enable the timer, rising edge should happen 0x0FFF timer counts later
TIM1_Cmd(ENABLE);
}
Thanks for any help you can give.
