// EasyNucleoIO.h
// David_Harris@hmc.edu 19 March 2017

// This library provides an Arduino-style interface to control I/O 
// devices on a STM32F042K6 device on a STM Nucleo board.

// The STM NUCLEO-F042K6 boad maps the STM32 pins to Arduino pin names
// as given in Table 9 of the datasheet:

//  Arduino Pin Name	STM32 Pin
//	D0					PA10
//  D1					PA9
//	D2					PA12
//	D3					PB0
//	D4					PB7
//	D5					PB6
//	D6					PB1
//	D7					PF0
//	D8					PF1
//	D9					PA8
//	D10					PA11
//	D11					PB5
//	D12					PB4
//	D13					PB3 (on-board green LED)
//	A0	(D14)			PA0
//	A1	(D15)			PA1
//	A2	(D16)			PA3
//	A3	(D17)			PA4
//	A4	(D18)			PA5
//	A5	(D19)			PA6
//	A6	(D20)			PA7
//	A7	(D21)			PA2

#include <stm32f042x6.h>

// Mapping of Dx pins to STM pins.
// 15:0  are STM PA15:0
// 23:16 are STM PB7:0
// 33:32 are STM PF1:0

// ARDUINO Pin Modes
#define INPUT  0
#define OUTPUT 1

// Delay constants
#define COUNTSPERMS 898

/////////////////////////////////////////////////////////////////////
// Helper functions for converting pin numbers
/////////////////////////////////////////////////////////////////////

int digitalPinMapping[22] = {10, 9, 12, 16, 23, 22, 17, 32, 33, 8, 11, 21, 20, 19, 
                             0, 1, 3, 4, 5, 6, 7, 2};
int analogPinMapping[8] = {0, 1, 3, 4, 5, 6, 7, 2};

GPIO_TypeDef* pinToReg(int pin) {
	int p = digitalPinMapping[pin];
	if (p < 16) return GPIOA;
	else if (p < 32) return GPIOB;
	else return GPIOF;
}

int pinToOffset(int pin) {
	int p = digitalPinMapping[pin];
	return p % 16;
}

/////////////////////////////////////////////////////////////////////
// Initialization
// This function must be called before any others are used
/////////////////////////////////////////////////////////////////////

void EasyNucleoIOInit(void) {
	//Clocks:	
	//enable clock for GPIOA, and GPIOB
	RCC->AHBENR |= RCC_AHBENR_GPIOAEN | RCC_AHBENR_GPIOBEN | 
	               RCC_AHBENR_GPIOFEN;

	//enable clock to SPI1
	RCC->APB2ENR |= RCC_APB2ENR_SPI1EN;	
}

/////////////////////////////////////////////////////////////////////
// GPIO Functions
/////////////////////////////////////////////////////////////////////

void pinMode(int pin, int function) {
	GPIO_TypeDef *gpio = pinToReg(pin);
	int offset = pinToOffset(pin)*2;	

	gpio->MODER &= ~((3 & ~function) << offset);
	gpio->MODER |=  ((3 &  function) << offset);
}

void digitalWrite(int pin, int val) {
	GPIO_TypeDef *gpio = pinToReg(pin);
	int offset = pinToOffset(pin);

	if (val) gpio->ODR |=  (1 << offset);
	else     gpio->ODR &= ~(1 << offset);
}

int digitalRead(int pin) {
	GPIO_TypeDef *gpio = pinToReg(pin);
	int offset = pinToOffset(pin);

	return (gpio->IDR >> offset) & 0x1;
}

/////////////////////////////////////////////////////////////////////
// Delay Functions
/////////////////////////////////////////////////////////////////////

void delayLoop(int ms) {
	// declare counter volatile so it isn't optimized away
	// countsperms empirically determined such that delayLoop(100) waits 100 ms
	volatile int i = COUNTSPERMS * ms;
	
	while (i--); // count down time
}