項目開源鏈接

github主頁	https://github.com/snqx-lqh
本項目github地址	https://github.com/snqx-lqh/STM32F103C8T6HalDemo
作者 VX	Qinghua-Li7

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項目說明

最近在做一個項目的時候，需要用到Max31850去讀取PT100的溫度值，使用的模塊如下

由于店家給的資料只有Arduino的，然后我就把Arduino庫中的OneWire庫修改成了STM32可移植的C語言代碼，使用函數指針面向對象設計，使得代碼移植性更強。具體的操作以及演示我也有在B站進行講解，DS18B20和MAX31850一樣使用的單總線協議，所以可以共同使用這個代碼。

移植講解

如果想要使用我移植好的OneWire庫，首先需要修改u_one_wire.c文件開頭的宏定義。需要用戶提供延時微秒的函數，以及使能和失能單片機中斷的函數。

#include "u_one_wire.h"/**************用戶處理的區域*****************/
#include "delay.h"#define noInterrupts()         __disable_irq();  //失能單片機中斷
#define interrupts()           __enable_irq();   //使能單片機中斷
#define one_wire_delay_us      DWT_Delay_us
/********************************************/

然后在max_31850.c，也就是傳感器處理文件中，建立一個one_wire的對象，并且實現對象中的方法。主要是設置引腳方向，引腳電平和讀取引腳的電平，我這里由于是使用的HAL庫，CubeMX將我的GPIO以及初始化了，所以這部分就不用管了，但是如果使用標準庫的話，也要添加引腳初始化。

/***************    用戶處理區域    ****************/#define max31850_delay_ms DWT_Delay_msstatic uint8_t gpio_init(void)
{return 0;
}static uint8_t set_pin_dir(one_wire_dir_t one_wire_dir)
{if(one_wire_dir == ONE_WIRE_DIR_IN){GPIOA->CRL&=0XFFFFFFF0;GPIOA->CRL|=8<<(4*0);}else if(one_wire_dir == ONE_WIRE_DIR_OUT){GPIOA->CRL&=0XFFFFFFF0;GPIOA->CRL|=3<<(4*0);}return 0;
}static  uint8_t set_pin_level(uint8_t level)
{if(0 == level){GPIOA->BRR  = GPIO_PIN_0;}else if(1 == level){GPIOA->BSRR = GPIO_PIN_0;}return 0;
}static uint8_t read_pin_level(void)
{uint8_t read_pin ;read_pin = HAL_GPIO_ReadPin(GPIOA,GPIO_PIN_0);return read_pin;
}one_wire_dev_t max31850={.init = gpio_init,.set_pin_dir = set_pin_dir,.set_pin_level= set_pin_level,.read_pin_level= read_pin_level,
};/**********************************************************/

最后在使用的時候，就可以參考Arduino中的步驟，先要定義一個初始化的函數，然后開始地址掃描、校驗、復位、選地址、轉換、讀取數據等一系列操作。

/*** @brief   初始化max31850，包含引腳初始化* @param   * @retval   **/
void max31850_init()
{one_wire_begin(&max31850);
}
/*** @brief   讀取max31850的溫度，帶掃描地址* @param   celsius：攝氏度 fahrenheit：華氏溫度* @retval  **/
int get_max31850_temp(float *celsius,float *fahrenheit)
{uint8_t i;uint8_t present = 0;uint8_t temptype;uint8_t data[12];uint8_t addr[8];if(celsius == NULL || fahrenheit == NULL)return -1;if ( !one_wire_search(&max31850,addr,true)) {one_wire_reset_search(&max31850);max31850_delay_ms(250);return -2;}if (crc8(addr, 7) != addr[7]) {return -3;}// the first ROM byte indicates which chipswitch (addr[0]) {case 0x10:temptype = TYPE_DS18S20;break;case 0x28:temptype = TYPE_DS18B20;break;case 0x22:temptype = TYPE_DS18S22;break;// ADDED SUPPORT FOR MAX31850!case 0x3B:temptype = TYPE_MAX31850;break;default:return -4;}one_wire_reset(&max31850);one_wire_select(&max31850,addr);one_wire_write(&max31850,0x44, 1);        // start conversion, with parasite power on at the endmax31850_delay_ms(1000);     // maybe 750ms is enough, maybe not// we might do a ds.depower() here, but the reset will take care of it.present = one_wire_reset(&max31850);one_wire_select(&max31850,addr);one_wire_write(&max31850,0xBE,0);         // Read Scratchpadfor ( i = 0; i < 9; i++) {           // we need 9 bytesone_wire_read(&max31850,&data[i]);}// Convert the data to actual temperature// because the result is a 16 bit signed integer, it should// be stored to an "int16_t" type, which is always 16 bits// even when compiled on a 32 bit processor.int16_t raw = (data[1] << 8) | data[0];if (temptype == TYPE_DS18S20) {raw = raw << 3; // 9 bit resolution defaultif (data[7] == 0x10) {// "count remain" gives full 12 bit resolutionraw = (raw & 0xFFF0) + 12 - data[6];}} else if (temptype == TYPE_MAX31850) {printf("--------------------------------\r\n");if (raw & 0x01) {return -4;}} else {uint8_t cfg = (data[4] & 0x60);// at lower res, the low bits are undefined, so let's zero themif (cfg == 0x00) raw = raw & ~7;  // 9 bit resolution, 93.75 mselse if (cfg == 0x20) raw = raw & ~3; // 10 bit res, 187.5 mselse if (cfg == 0x40) raw = raw & ~1; // 11 bit res, 375 ms default is 12 bit resolution, 750 ms conversion time}*celsius = (float)raw / 16.0;*fahrenheit = *celsius * 1.8 + 32.0;return 0;
}

還可以跳過掃描階段，直接獲取數據，這種方式比較適合單節點的獲取。就是電路上只連接了一個DS18B20或者MAX31850。

/*** @brief   讀取max31850的溫度，跳過地址掃描* @param   celsius：攝氏度 fahrenheit：華氏溫度* @retval  **/
int get_max31850_temp_skiprom(float *celsius,float *fahrenheit)
{uint8_t i;uint8_t present = 0;uint8_t temptype;uint8_t data[12];uint8_t addr[8];if(celsius == NULL || fahrenheit == NULL)return -1;one_wire_reset(&max31850);one_wire_skip(&max31850);one_wire_write(&max31850,0x44, 1);        // start conversion, with parasite power on at the endmax31850_delay_ms(1000);     // maybe 750ms is enough, maybe not// we might do a ds.depower() here, but the reset will take care of it.present = one_wire_reset(&max31850);one_wire_skip(&max31850);one_wire_write(&max31850,0xBE,0);         // Read Scratchpadfor ( i = 0; i < 9; i++) {                // we need 9 bytesone_wire_read(&max31850,&data[i]);}int16_t raw = (data[1] << 8) | data[0];if (raw & 0x01) {return -4;}*celsius = (float)raw / 16.0;*fahrenheit = *celsius * 1.8 + 32.0;return 0;
}