/* p7_2.c: On-chip temperature sensor
 * This program converts the on-chip temperature sensor output
 * and display the temperature in Celsius on the console.
 * Timer TIM3 is configured to generate 1 Hz output, which is
 * used to trigger the A/D conversion. The internal temperature
 * sensor is connected to channel 16 of ADC1 Master. The sensor
 * is turned on at bit 23 of ADC_CCR register.
 *
 * The conversion result is displayed as Celsius on the console
 * using the formula and parameters in the datasheet.
 * 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>

/* Temperature sensor calibration value address */
#define TEMP30_CAL_ADDR ((uint16_t*)((uint32_t)0x1FFFF7B8))     // The ADC value in 30 degrees Celsius saved here by factory
#define TEMP110_CAL_ADDR ((uint16_t*)((uint32_t)0x1FFFF7C2))	// The ADC value in 110 degrees Celsius saved here by factory

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

int main(void)
{
	uint32_t data;
	double temp, y1, y2, x1, x2, m;  /* will contain the temperature in degrees Celsius */

	RCC->AHBENR |=  0x00020000;     /* enable GPIOA clock */

	/* setup TIM3 */
	RCC->APB1ENR |= 0x00000002;     /* enable TIM3 clock */
	TIM3->PSC = 800 - 1;            /* divided by 800 */
	TIM3->ARR = 10000 - 1;          /* divided by 10000, sample at 1 Hz */
	TIM3->CNT = 0;
	TIM3->CCMR1 = 0x00006800;       /* pwm1 mode,  preload enable */
	TIM3->CCER = 0x0010;            /* ch2 enable */
	TIM3->CCR2 = 50 - 1;
	TIM3->CR2 = 0x00000020;         /* The update event is selected as trigger output */
	TIM3->CR1 = 1;                  /* enable timer3 */

	/* setup ADC1 */
	RCC->APB2ENR |= 0x00000200;     /* enable ADC1 clock */

	/* calibrate ADC*/
	ADC1->CR = 0x80000000;
	while(ADC1->CR & 0x80000000);

	/* turn on the temp sensor */
	/* configure A to D converter */
	ADC1->CHSELR = (1 << 16); /* ch16 - internal temp sensor, single channel */
	ADC1->SMPR = 0x00000007;  /* Select a sampling mode of 239.5 ADC clk to be greater than 17.1us */
	ADC->CCR |= (1 << 23);
	ADC1->CFGR1 = 0x000004C0; /* trigger: EXTEN rising edge, EXTSEL 3 = TIM3_TRGO */
	ADC1->CFGR2 = 0;
	ADC1->CR |= 1;            /* enable ADC1 */

	/* initialize USART2 for output */
	USART2_init();
	printf("ADC internal temperature sensor \r\n");

	y1 = 30;
	y2 = 110;
	x1 = *TEMP30_CAL_ADDR;
	x2 = *TEMP110_CAL_ADDR;
	m = (y2 - y1)/(x2-x1);

	ADC1->CR |= 0x00000004;                         /* start a conversion */
	while (1) {
		while (!(ADC1->ISR & 4)) {
		}
		ADC1->ISR = 0xFFFF;
		data = ADC1->DR;
		temp = m*((double)data - x1) + y1;          /* Calculate temperature */
		printf("%d, %.2f%cC\r\n", data, temp, 176); /* octal 176 is degree sign in ASCII */
	}
}

/* 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 */
}