Hands-On: GPIO & Timer Driver in C

/* GPIO HAL: portable driver for Aurix TC3xx Port module */
#include 
#include "Std_Types.h"

/* Port register structure (Aurix P00..P34) */
typedef struct {
    volatile uint32_t OUT;    /* +0x00: output register */
    volatile uint32_t OMR;    /* +0x04: output modification register (atomic set/clr) */
    volatile uint32_t reserved08[2];
    volatile uint32_t IOCR0;  /* +0x10: I/O control 0–3 */
    volatile uint32_t IOCR4;  /* +0x14: I/O control 4–7 */
    volatile uint32_t IOCR8;  /* +0x18: I/O control 8–11 */
    volatile uint32_t IOCR12; /* +0x1C: I/O control 12–15 */
    volatile uint32_t reserved20[4];
    volatile uint32_t IN;     /* +0x30: input register */
} Port_Regs_t;

#define PORT0_BASE  0xF003A000u
#define PORT(n)     ((Port_Regs_t *)(PORT0_BASE + (n) * 0x100u))

/* Aurix OMR: PS (set) bits [7:0]; PCL (clear) bits [23:16] */
#define PORT_OMR_SET(pin)   (1u << (pin))
#define PORT_OMR_CLR(pin)   (1u << ((pin) + 16u))

void Gpio_SetOutput(uint8_t port, uint8_t pin) {
    PORT(port)->OMR = PORT_OMR_SET(pin);  /* atomic set via OMR */
}
void Gpio_ClearOutput(uint8_t port, uint8_t pin) {
    PORT(port)->OMR = PORT_OMR_CLR(pin); /* atomic clear via OMR */
}
uint8_t Gpio_ReadInput(uint8_t port, uint8_t pin) {
    return (uint8_t)((PORT(port)->IN >> pin) & 0x01u);
}
void Gpio_ToggleOutput(uint8_t port, uint8_t pin) {
    /* Set and clear in same write: toggle */
    PORT(port)->OMR = PORT_OMR_SET(pin) | PORT_OMR_CLR(pin);
}

/* Aurix STM (System Timer Module): 64-bit free-running counter */
/* 300 MHz → 1 tick = 3.33 ns; wraps after ~1.95 years */
#include 

#define STM0_BASE   0xF0001000u

typedef struct {
    volatile uint32_t CLC;      /* +0x00: Clock Control */
    volatile uint32_t reserved04;
    volatile uint32_t ID;       /* +0x08: Module ID */
    volatile uint32_t reserved0C;
    volatile uint32_t TIM0;     /* +0x10: Timer register 0 (lower 32 bits) */
    volatile uint32_t TIM1;     /* +0x14: Timer register 1 (bits 32-63) */
    volatile uint32_t TIM2;     /* +0x18: Timer register 2 (bits 4-35) */
    volatile uint32_t TIM3;     /* +0x1C: Timer register 3 (bits 8-39) */
    volatile uint32_t TIM4;     /* +0x20: Timer register 4 (bits 12-43) */
    volatile uint32_t TIM5;     /* +0x24: Timer register 5 (bits 16-47) */
    volatile uint32_t TIM6;     /* +0x28: Timer register 6 (upper 32 bits) */
    volatile uint32_t CAP;      /* +0x2C: Capture register */
} Stm_Regs_t;

#define STM0  ((Stm_Regs_t *)STM0_BASE)

#define STM_TICKS_PER_US  300u   /* 300 MHz */
#define STM_TICKS_PER_MS  300000u

uint32_t Stm_GetTick(void)       { return STM0->TIM0; }

void Stm_DelayUs(uint32_t us) {
    uint32_t start = Stm_GetTick();
    uint32_t ticks = us * STM_TICKS_PER_US;
    while ((Stm_GetTick() - start) < ticks) { /* busy wait */ }
}

boolean Stm_HasElapsed(uint32_t start_tick, uint32_t period_us) {
    return (boolean)((Stm_GetTick() - start_tick) >= (period_us * STM_TICKS_PER_US));
}

/* Software PWM using STM timer: 1 kHz PWM, 0–100% duty cycle */
#include 
#include "gpio_driver.h"
#include "timer_driver.h"

#define PWM_PERIOD_US   1000u   /* 1 ms = 1 kHz */
#define LED_PORT        2u
#define LED_PIN         4u

static uint8_t  g_duty_pct = 50u;     /* 0–100% */
static uint32_t g_pwm_start_tick;
static boolean  g_phase_high;

void Pwm_Init(void) {
    Gpio_SetOutputMode(LED_PORT, LED_PIN);
    g_pwm_start_tick = Stm_GetTick();
    g_phase_high     = TRUE;
    Gpio_SetOutput(LED_PORT, LED_PIN);
}

void Pwm_MainFunction(void) {  /* called every 100 µs from OS task */
    uint32_t elapsed_us = (Stm_GetTick() - g_pwm_start_tick) / STM_TICKS_PER_US;

    if (g_phase_high && (elapsed_us >= g_duty_pct * (PWM_PERIOD_US / 100u))) {
        Gpio_ClearOutput(LED_PORT, LED_PIN);  /* end of ON phase */
        g_phase_high = FALSE;
    }
    if (elapsed_us >= PWM_PERIOD_US) {
        Gpio_SetOutput(LED_PORT, LED_PIN);    /* start new cycle */
        g_pwm_start_tick = Stm_GetTick();
        g_phase_high = TRUE;
    }
}

void Pwm_SetDuty(uint8_t duty_pct) {
    g_duty_pct = (duty_pct > 100u) ? 100u : duty_pct;
}