MAX31855热电偶转换器开发流程

开发板

MAX31855热电偶转换器开发流程

一、准备硬件和相关知识

实验连接图

1.硬件：一块开发板、逻辑分析仪、热电偶（常用的K型热电偶）、杜邦线等；

2.相关知识：VHDL基础、SPI通信；

二、max31855datasheet编程用到的部分：

图1 电路连接图

图2 串行接口时序特性

图3 串口时序

图4 引脚分配

图5 热电偶温度格式

三、程序编写

/**

******************************************************************************

* @file : max31855.c

* @Brief : MAX31855 cold-junction compensated thermocouple-to-digital

* converter program body.

******************************************************************************

*

* Copyright (c) respeke, www.etdev.net

*

******************************************************************************

*/

/* Includes ------------------------------------------------------------------*/

#include "max31855.h"

#include "STM32f1xx_hal.h"

/* External variables --------------------------------------------------------*/

SPI_HandleTypeDef hspi1;

/* Private variables ---------------------------------------------------------*/

float tcTemp = 0, cjTemp = 0;

bool tcError = false;

/* Private function prototypes -----------------------------------------------*/

/**

* @brief Delay about 11ns per NOP (72MHz*1.25MIPS/MHz=90MIPS)

* @param None

* @retval None

*/

static void SPI_Delay(uint32_t counter)

{

for(int i=0; i

{

__NOP();

}

………………………………………………

四、编程中注意的问题

把握时序图，严格核准。

五、波形图分析（室温约为20摄氏度）

热电偶输出，是以高位先输出。

胡章明 · 2020-3-22 08:55:03

新的内容，应该学习学习

junyunlai1 · 2020-3-24 22:23:21

编写头文件
1）common.h
#ifndef _COMMON_H_
#define _COMMON_H_

#define __DEBUG

#ifdef __DEBUG
#define DEBUG(format, args...)
      printf("FAHW-Lib: " format, ## args)
#else
#define DEBUG(format, args...)
#endif

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include

extern void clearLastError();
extern void setLastError(const char *fmt, ...);

#define EXPORT
extern int writeValueToFile(char* fileName, char* buff);
extern int writeIntValueToFile(char* fileName, int value);
extern int readValueFromFile(char* fileName, char* buff, int len);
extern int readIntValueFromFile(char* fileName);

#define FILE_PATH_LENGTH          (128)

#endif

2）libfahw-filectl.h
#ifndef __FRIENDLYARM_HARDWARE_FILECTRL_H__
#define __FRIENDLYARM_HARDWARE_FILECTRL_H__

int openHW(const char *devName, int flags);
int writeHW(int fd, const void *_data, size_t len);
int readHW(int fd, void *_data, size_t len);
int selectHW(int fd, int sec, int usec);
void closeHW(int fd);
int ioctlWithIntValue(int fd, int cmd, int value);

#endif

3）libfahw-spi.h
#ifndef __FRIENDLYARM_HARDWARE_SPI_H__
#define __FRIENDLYARM_HARDWARE_SPI_H__

// SPIBitOrder
#define LSBFIRST  (0)  ///< LSB First
#define MSBFIRST  (1) ///< MSB First

// SPIMode
#define SPI_MODE0  (0)  ///< CPOL  (0, CPHA  (0
#define SPI_MODE1  (1)  ///< CPOL  (0, CPHA  (1
#define SPI_MODE2  (2)  ///< CPOL  (1, CPHA  (0
#define SPI_MODE3  (3)  ///< CPOL  (1, CPHA  (1

#define SPI_CPHA  (0x01)
#define SPI_CPOL  (0x02)
#define SPI_CS_HIGH  (0x04)
#define SPI_LSB_FIRST  (0x08)
#define SPI_3WIRE  (0x10)
#define SPI_LOOP  (0x20)
#define SPI_NO_CS  (0x40)
#define SPI_READY  (0x80)

// SPIClockDivider
#define SPI_CLOCK_DIV65536  (0)    ///< 65536  (256us  (4kHz
#define SPI_CLOCK_DIV32768  (32768) ///< 32768  (126us  (8kHz
#define SPI_CLOCK_DIV16384  (16384) ///< 16384  (64us  (15.625kHz
#define SPI_CLOCK_DIV8192 (8192) ///< 8192  (32us  (31.25kHz
#define SPI_CLOCK_DIV4096 (4096) ///< 4096  (16us  (62.5kHz
#define SPI_CLOCK_DIV2048 (2048) ///< 2048  (8us  (125kHz
#define SPI_CLOCK_DIV1024 (1024) ///< 1024  (4us  (250kHz
#define SPI_CLOCK_DIV512 (512)    ///< 512  (2us  (500kHz
#define SPI_CLOCK_DIV256 (256)    ///< 256  (1us  (1MHz
#define SPI_CLOCK_DIV128 (128)    ///< 128  (500ns  (= 2MHz
#define SPI_CLOCK_DIV64    (64)    ///< 64  (250ns  (4MHz
#define SPI_CLOCK_DIV32    (32)    ///< 32  (125ns  (8MHz
#define SPI_CLOCK_DIV16    (16)    ///< 16  (50ns  (20MHz
#define SPI_CLOCK_DIV8    (8)    ///< 8  (25ns  (40MHz
#define SPI_CLOCK_DIV4    (4)    ///< 4  (12.5ns 80MHz
#define SPI_CLOCK_DIV2    (2)    ///< 2  (6.25ns  (160MHz
#define SPI_CLOCK_DIV1    (1)    ///< 0  (256us  (4kHz