HomeEnergyMeter/STM32/Core/Src/oneWireDriver.c

#include "stm32f1xx_hal.h"
#include<stdio.h>

#define DS18B20_PIN GPIO_PIN_14
#define DS18B20_PORT GPIOC

void us_delay(uint16_t delay)
{
    TIM1->CNT = 0;
    while (TIM1->CNT < delay);
}

/**
 * Control registers for F1xx GPIOs are 2 x 2 bits
 * For Port C, CRH, pin 14 bits 27-24
 * CNF: Input mode: 01=Float input  Output mode: 01=Open-drain (Reset stage is 01)
 * MODE: 00=Input   10=Out 2 MHz
 *
 * So bits should be for                   |   XXXX                       |
 * Input:  0100     AND-Mask: 0xF4FFFFFF   11110100111111111111111111111111
 * Output: 0110      OR-Mask: 0x06000000   00000110000000000000000000000000
 *
 * For init use OR 0x04000000 and then AND 0xF4FFFFFF = Input
 *
 */
void init_gpio_pin(void)
{
    DS18B20_PORT->CRH |= 0x04000000;
    DS18B20_PORT->CRH &= 0xF4FFFFFF;
}
void gpio_set_input(void)
{
    DS18B20_PORT->CRH &= 0xF4FFFFFF;
    DS18B20_PORT->BSRR = (1 << 14);
}

void gpio_set_output(void)
{
    DS18B20_PORT->BSRR = (1 << 14);
    DS18B20_PORT->CRH |= 0x06000000;
}

int readInput()
{
    if (((DS18B20_PORT->IDR) & (1 << 14)) == 0)
        return 0;
    else
        return 1;
}

void writeBitHigh()  { DS18B20_PORT->BSRR = (1 << 14); }
void writeBitLow() { DS18B20_PORT->BSRR = (1 << 30); }

void writeSlot(uint8_t data) {
	gpio_set_output(); // set as output
	if( data == 1 ) {
		// write 1
		writeBitLow();
		us_delay(1);
		writeBitHigh();
		us_delay(64);
	}
	else {
		// write 0
		writeBitLow();
		us_delay(65);
		writeBitHigh();
	}
	gpio_set_input();
	us_delay(5);
}


uint8_t readSlot(void) {
	uint8_t retVal = 0;
    gpio_set_output(); // set as output
    writeBitLow();
    us_delay(1);
    writeBitHigh();
    gpio_set_input();  // 2.5mS has passed
    us_delay(10);	   // 12.5mS has passed
    if (readInput() == 1) // if the pin is HIGH
    {
    	retVal = 1;
    }
    us_delay(55);
    return retVal;
}

void writeByte(uint8_t data)
{
    for (int i = 0; i < 8; i++)
    {
    	writeSlot( ((data & (1 << i)) == 0) ? 0:1 );
    }
}


uint8_t readByte(void)
{
    uint8_t value = 0;

    for (int i = 0; i < 8; i++)
    {
        if (readSlot() == 1) value |= 1 << i;
    }
    return value;
}

uint8_t oneWire_init(void)
{
    volatile int i;
    uint8_t retVal = 0;

    gpio_set_output();
    writeBitLow();
    us_delay(500);
    writeBitHigh();
    gpio_set_input();

    us_delay(20);

    for(i=0;i<48;i++) {     // We must wait minimum 480uS in total. Every loop is 10uS

        if( readInput() == 0 ) retVal = 1; // Ok, sensor was found
        us_delay(10);
    }

    return retVal;
}