Servo_Driver.c

#include "stm32f10x.h"
#include "system_stm32f10x.h"
#include "GPIO_Driver.h"
#include "Servo_Driver.h"

void servo_init(uint8_t timer, uint8_t channel)
{
    GPIO_TYPE PWM_Output_Servo;
    TIM_TypeDef *timerPort = TIM2;
    uint8_t channelOffset = 0;

    PWM_Output_Servo.mode = OUTPUT;
    PWM_Output_Servo.mode_type = OUTPUT_ALT_FUNCTION;
    PWM_Output_Servo.speed = SPEED_50MHZ;

    switch(timer)
    {
        case 2:
            timerPort = TIM2;
            RCC->APB1ENR |= RCC_APB1ENR_TIM2EN;

            if(channel == 1)
            {
                    PWM_Output_Servo.port = PORTA;
                    PWM_Output_Servo.pin = 15;
            }
            else if(channel == 2)
            {
                    PWM_Output_Servo.port = PORTA;
                    PWM_Output_Servo.pin = 1;
            }
            else if(channel == 3)
            {
                PWM_Output_Servo.port = PORTA;
                PWM_Output_Servo.pin = 2;
            }
            else
            {
                PWM_Output_Servo.port = PORTA;
                PWM_Output_Servo.pin = 3;
            }

        break;

        case 3:
            timerPort = TIM3;
            RCC->APB1ENR |= RCC_APB1ENR_TIM3EN;

            if(channel == 1)
            {
                    PWM_Output_Servo.port = PORTA;
                    PWM_Output_Servo.pin = 6;
            }
            else if(channel == 2)
            {
                    PWM_Output_Servo.port = PORTA;
                    PWM_Output_Servo.pin = 7;
            }
            else if(channel == 3)
            {
                PWM_Output_Servo.port = PORTB;
                PWM_Output_Servo.pin = 0;
            }
            else
            {
                PWM_Output_Servo.port = PORTB;
                PWM_Output_Servo.pin = 1;
            }

        break;

        case 4:
            timerPort = TIM4;
            RCC->APB1ENR |= RCC_APB1ENR_TIM4EN;

            if(channel == 1)
            {
                    PWM_Output_Servo.port = PORTB;
                    PWM_Output_Servo.pin = 6;
            }
            else if(channel == 2)
            {
                    PWM_Output_Servo.port = PORTB;
                    PWM_Output_Servo.pin = 7;
            }
            else if(channel == 3)
            {
                PWM_Output_Servo.port = PORTB;
                PWM_Output_Servo.pin = 8;
            }
            else
            {
                PWM_Output_Servo.port = PORTB;
                PWM_Output_Servo.pin = 9;
            }
        break;
    }

    switch(channel)
    {
        case 1:
            channelOffset = 0;
            //enable PWM mode 1 and the preloader for channel 4
            timerPort->CCMR1 |= TIM_CCMR1_OC1M_1 | TIM_CCMR1_OC1M_2 | TIM_CCMR1_OC1PE;
        break;

        case 2:
            channelOffset = 4;
            //enable PWM mode 1 and the preloader for channel 4
            timerPort->CCMR1 |= TIM_CCMR1_OC2M_1 | TIM_CCMR1_OC2M_2 | TIM_CCMR1_OC2PE;
        break;

        case 3:
            channelOffset = 8;
            //enable PWM mode 1 and the preloader for channel 4
            timerPort->CCMR2 |= TIM_CCMR2_OC3M_1 | TIM_CCMR2_OC3M_2 | TIM_CCMR2_OC3PE;
        break;

        case 4:
            channelOffset = 12;
            //enable PWM mode 1 and the preloader for channel 4
            timerPort->CCMR2 |= TIM_CCMR2_OC4M_1 | TIM_CCMR2_OC4M_2 | TIM_CCMR2_OC4PE;
        break;
    }

    init_gpio(PWM_Output_Servo);

    //init AFIO clock
    RCC->APB2ENR |= RCC_APB2ENR_AFIOEN;

    //enable capture/compare for specified channel
    timerPort->CCER |= (1<<channelOffset);

    //init the ARR
    timerPort->CR1 |= TIM_CR1_ARPE;


    //enable duty cycle
    timerPort->PSC = 1440;
    timerPort->ARR = 1000; // 50Hz for servo control

    //enable the update generation and turn timer on
    timerPort->EGR |= TIM_EGR_UG;
    timerPort->CR1 |= TIM_CR1_CEN;
}

void servo_writeMicroseconds(int microseconds, uint8_t timer, uint8_t channel)
{
    uint16_t dutyCycle = 0;
    TIM_TypeDef *timerPort = TIM3;

    switch(timer)
    {
        case 2:
            timerPort = TIM2;
        break;
        case 3:
            timerPort = TIM3;
        break;
        case 4:
            timerPort = TIM4;
        break;
    }

    //servos have a range of 180 degrees, and the duty cycle in ms from 0-180 degrees equals
    //1ms to 2ms. Because of this, I wanted the input to be of longer range, so I have the user
    //input the time they want in microseconds from 1000-2000. The equation below sets
    //the dutyCycle variable to a proportional value from microseconds to a value that can be
    //given to the timers CCRx register. for example, if the user wants to move the servo to 0
    //degrees, the user passes in 1000, this will be divided by 20000.0 to equal 0.05. 0.05 will
    //be multiplied by timerPort->ARR (which is 1000) to equal 50. 50 is now a number that can
    //be set to the timers CCRx register to give a duty cycle of 5% (1ms pulse over a period of 20ms(50hz))
    dutyCycle = (uint16_t)((microseconds/20000.0)*(timerPort->ARR));

    switch(channel)
    {
        case 1:
            timerPort->CCR1 = dutyCycle;
            break;
        case 2:
            timerPort->CCR2 = dutyCycle;
            break;
        case 3:
            timerPort->CCR3 = dutyCycle;
            break;
        case 4:
            timerPort->CCR4 = dutyCycle;
            break;
    }
}