/* p7_3.c: LM34 Fahrenheit temperature sensor
 *
 * LM34 is a Fahrenheit temperature sensor with the output of
 * 10 mV/degreeF. The program assumes an LM34 connected to
 * pin PA4 (channel 4). The conversion result is displayed one
 * the console as degree Fahrenheit.
 * The console UART driver is from Program 4-5.
 *
 * This program was tested with Keil uVision v5.23 with DFP v2.0.0.
 */

#include "stm32f0xx.h"
#include <stdio.h>

void USART2_init(void);
int USART2_write(int c);
void delayMs(int n);

int main(void)
{
	int result;
	double temp;

	/* set up pin PA4 for analog input */
	RCC->AHBENR |=  0x00020000;     /* enable GPIOA clock */
	GPIOA->MODER |=  3<<8;          /* PA4 analog */

	/* setup ADC1 */
	RCC->APB2ENR |= 0x00000200;     /* enable ADC1 clock */
	ADC1->CR = 0;                   /* SW trigger */
	ADC1->CFGR1 = 0;
	ADC1->CFGR2 = 0;
	ADC1->CHSELR = 1 << 4;
	ADC1->CR |= 1;                  /* enable ADC1 */

	/* initialize USART2 for output */
	USART2_init();
	printf("LM34 Temperature Sensor\r\n");

	while (1) {
		ADC1->CR |= 4;          /* start a conversion */
		while (!(ADC1->ISR & 2)) {
		}                       /* wait for conv complete */
		result = ADC1->DR;      /* read conversion result */
		temp = (double)result / 4095 * 330;
		printf("%d, %.2f\r\n", result, temp);
		delayMs(1000);
	}
}

/* initialize USART2 to transmit at 9600 Baud */
void USART2_init(void)
{
	RCC->AHBENR |= 0x00020000;      /* Enable GPIOA clock */
	RCC->APB1ENR |= 0x00020000;     /* Enable USART2 clock */

	/* Configure PA2, PA3 for USART2 TX, RX */
	GPIOA->AFR[0] &= ~0xFF00;
	GPIOA->AFR[0] |=  0x1100;       /* alt1 for USART2 */
	GPIOA->MODER &= ~0x00F0;
	GPIOA->MODER |=  0x00A0;        /* enable alt. function for PA2, PA3 */

	USART2->BRR = 0x0341;           /* 9600 baud @ 8 MHz */
	USART2->CR1 = 0x000C;           /* enable Tx, Rx, 8-bit data */
	USART2->CR2 = 0x0000;           /* 1 stop bit */
	USART2->CR3 = 0x0000;           /* no flow control */
	USART2->CR1 |= 0x0001;          /* enable USART2 */
}

/* Write a character to USART2 */
int USART2_write(int ch)
{
	while (!(USART2->ISR & 0x0080)) {
	}                                // wait until Tx buffer empty
	USART2->TDR = (ch & 0xFF);
	return ch;
}

/* The code below is the interface to the C standard I/O library.
 * All the I/O are directed to the console, which is UART2.
 */
struct __FILE { int handle; };
FILE __stdout = { 1 };

/* Called by C library console/file output */
int fputc(int c, FILE *f)
{
	return USART2_write(c); /* write the character to console */
}


/* 8 MHz SYSCLK */
void delayMs(int n)
{
	int i;

	for (; n > 0; n--)
		for (i = 0; i < 1142; i++);
}