// Functions to manage the GPIO peripheral:
//   - configure direction, mode and pull-up/pull-down for a set of GPIO pins
//   - configure output mode for a set of GPIO pins
//   - configure alternative function mapping
//   - configure an EXTI line


#include "gpio.h"


// Set the direction, mode and pull-up for a set of GPIO pins on a given GPIO port
// input:
//   GPIOx - pointer to a GPIO peripheral handle
//   Mode - pin mode (one of GPIO_Mode_xx values)
//   PUPD - pull-up configuration (one of GPIO_PUPD_xx values)
//   Pins - set of pins (ORed combination of GPIO_Pin_X values)
void GPIO_set_mode(GPIO_TypeDef *GPIOx, GPIOMode_TypeDef Mode, GPIOPUPD_TypeDef PUPD, uint16_t Pins) {
	uint16_t pin = 0;
	uint32_t MODER = GPIOx->MODER;
	uint32_t PUPDR = GPIOx->PUPDR;

	// Set the configuration only for the pins mentioned in Pins parameter
	while (pin < 16) {
		if ((1 << pin) & Pins) {
			// Pin mode
			MODER &= ~GPIO_MODE_MSK(pin);
			MODER |=  GPIO_MODE_SET(pin,Mode);

			// Pull-up configuration
			PUPDR &= ~GPIO_PUPD_MSK(pin);
			PUPDR |=  GPIO_PUPD_SET(pin,PUPD);
		}
		pin++;
	}

	// Write new values of the mode and pull-up/pull-down control registers
	GPIOx->MODER = MODER;
	GPIOx->PUPDR = PUPDR;
}

// Set the type and speed for a set of GPIO pins configured as output on a given GPIO port
// input:
//   GPIOx - pointer to a GPIO peripheral handle
//   OT - output type of the GPIO pin (one of GPIOOT_xx values)
//   Speed - output speed of the GPIO pin (one of GPIOSPD_xx values)
//   Pins - set of pins (ORed combination of GPIO_Pin_X values)
void GPIO_out_cfg(GPIO_TypeDef *GPIOx, GPIOOT_TypeDef OT, GPIOSPD_TypeDef Speed, uint16_t Pins) {
	uint16_t pin = 0;
	uint32_t OSPEEDR = GPIOx->OSPEEDR;

	// Set output type only for the pins mentioned in Pins parameter
	if (OT == GPIO_OT_PP) {
		GPIOx->OTYPER &= ~Pins;
	} else {
		GPIOx->OTYPER |=  Pins;
	}

	// Set the configuration only for the pins mentioned in Pins parameter
	while (pin < 16) {
		if ((1 << pin) & Pins) {
			// Set output speed
			OSPEEDR &= ~GPIO_SPD_MSK(pin);
			OSPEEDR |=  GPIO_SPD_SET(pin,Speed);
		}
		pin++;
	}

	// Write new value of the speed control register
	GPIOx->OSPEEDR = OSPEEDR;
}

// Set the alternative function mapping for a GPIO pin on a given GPIO port
// input:
//   GPIOx - pointer to a GPIO peripheral handle
//   Pin - specified the pin for the alternative function (one of GPIO_PinSourceXX values)
//   AF - pin alternative function number, to know which functions are multiplexed on each GPIO pin,
//        refer to the MCU datasheet (table "Alternate function input/output")
void GPIO_af_cfg(GPIO_TypeDef *GPIOx, uint16_t Pin, uint8_t AF) {
	uint32_t AFR = GPIOx->AFR[Pin >> 3];

	// Set the alternative function for a GPIO pin
	AFR &= ~GPIO_AF_MSK(Pin & 0x07);
	AFR |=  GPIO_AF_SET(Pin & 0x07,AF);

	// Write new value of the alternate function register
	GPIOx->AFR[Pin >> 3] = AFR;
}

// Initialize the EXTI peripheral according to the specified parameters
// input:
//   EXTI_Line - specifies the EXTI line(s)
//   mode - mode of the EXTI line (one of EXTIMODE_XXX values)
//   trigger - trigger signal active edge (one of EXTI_TRG_XXX values)
// note: the SYSCFG peripheral must be enabled
void GPIO_EXTI_cfg(uint32_t EXTI_Line, EXTIMode_TypeDef mode, EXTITRG_TypeDef trigger) {
	// Clear IT pending bit for EXTI line
	EXTI->PR = EXTI_Line;

	// Clear EXTI line configuration
	EXTI->IMR  &= ~EXTI_Line;
	EXTI->EMR  &= ~EXTI_Line;
	EXTI->RTSR &= ~EXTI_Line;
	EXTI->FTSR &= ~EXTI_Line;

	// Enable IRQ generation
	if (mode & EXTI_MODE_IRQ) EXTI->IMR |= EXTI_Line;

	// Enable event generation
	if (mode & EXTI_MODE_EVT) EXTI->EMR |= EXTI_Line;

	// Enable trigger on rising edge
	if (trigger & EXTI_TRG_RISING) EXTI->RTSR |= EXTI_Line;

	// Enable trigger on falling edge
	if (trigger & EXTI_TRG_FALLING) EXTI->FTSR |= EXTI_Line;
}

// Select the GPIO pin used as EXTI line
// input:
//   portsrc - a GPIO port to be used as source for EXTI lines (one of EXTI_PortSourceGPIOx values)
//   pinsrc - the EXTI line to be configured (one of EXTI_PinSourceX values)
// note: the SYSCFG peripheral must be enabled
void GPIO_EXTI_src(uint8_t portsrc, uint8_t pinsrc) {
	uint32_t EXTICR;
	uint8_t  shift = (pinsrc & 0x03) << 2;

	EXTICR = SYSCFG->EXTICR[pinsrc >> 2];
	EXTICR &= ~(0x0F << shift);
	EXTICR |= portsrc << shift;
	SYSCFG->EXTICR[pinsrc >> 2] = EXTICR;
}