设计构想

步入正题之前先絮叨絮叨没用的。
本设计构想源自于笔者祖父。祖父年事已高，虽然说身子骨还算硬朗，但是毕竟机体的老化是不可避免的，所以还是存在着诸多身体问题。但是老人家有着待不住的性格，时不时就要拎起拐杖出去转转，但是毕竟岁数大了，多少都有一些隐患。不让他出去也不好，跟他出去他又不自在，让他自己出去随便走又感觉不放心，所以就萌生了这个想法，做一款远程监护拐杖，这样就可以一定程度上实现对于他的远程监护——不跟在他身边给他充分的自由，又能一定程度上知道他现在状态怎么样。
笔者现在大三，生物医学工程专业，虽然以前也做过相关的穿戴式传感器项目，但是这一次涉及到生活状态下特别是有运动的测量，而且有着硬件体量的限制，难度相对而言还是比较大的。所以，暂时确定这一批的生成日记针对的是第一代的老年人远程监护拐杖。之后如果有就会进行改进，还可以有第二代、第三代、甚至更多更强大的设计。

硬件清单

本设计需要用到的硬件比较少，仅需要一个Arduino UNO开发板、HXDZ-30102血氧检测模块以及一个ZS040蓝牙模块。前面一阶段的开发测试主要借助PC机作为上位机，而后一阶段则会结合Android系统的手机App实现。

【HXDZ-30102血样监测模块（核心为MAX30102血氧检测芯片）】

【Arduino UNO 开发板】

【ZS-040蓝牙模块】

硬件连接

本篇作为这个系列的第一弹，主要针对于ArduinoUNO开发板与HXDZ30102血氧监测模块的硬件连接。蓝牙模块的相关连接将会在第三弹中进行介绍。
由于心电监测模块已经把相关的引脚封装的比较好，因而已经可以比较好地实现了与Arduino开发板的直接对接，硬件链接也是相当的简单明了。血氧监测模块共有5个引脚，分别是VCC（电源）、GND（地）、SCL（I2C通讯时钟）、SDA（I2C通讯数据）和INT（中断服务信号）。按照程序设计（程序会在下一个部分展现），只需要把电源与接地连接到Arduino板子上面提供的5V电源接口与GND上，而SCL与SDA只需要直接接在Arduino相应的SCL与SDA上即可，而剩下的管脚INT需要接在ArduinoUNO的Pin10上。

【ArduinoUNO引脚功能分布图】
（摘自Arduino中断例程及常用arduino开发板中断引脚汇总）

相关程序

HXDZ30102的程序已经有人进行了相应的开发，并已经在GitHub上进行了开源。
对于原始代码，这里就不再赘述，请直接参考Arduino C code for MAX30102 pulse oximetry sensor (MAXIM Integrated, Inc.)
这个程序有着自己的输出模式，把结果按照自己的方式进行了实时更新。虽然这种机制比较合理，但是对于我们的设计需求存在着一定程度的限制。限制主要存在于两个方面——输出方式和数据处理能力，针对这些方面的改进我会在下一篇博客中进行说明。
原始程序的工作流程大致上是这样的：首先进入等待状态，等待从PC端通过串口对单片机传送信息，作为一个上位机准备完毕可以实时接收数据的信号。单片机接受到这个信号之后，开始进入测量状态，按照25Hz的采样频率读取红光波段与红外波段的信号，记录数据并进行数据的相应处理，计算得到相关数据。可以参考下面的主程序进行理解：

/** \file RD117_LILYPAD.ino ******************************************************
*
* Project: MAXREFDES117#
* Filename: RD117_LILYPAD.ino
* Description: This module contains the Main application for the MAXREFDES117 example program.
*
* Revision History:
*\n 1-18-2016 Rev 01.00 GL Initial release.
*\n
*
* --------------------------------------------------------------------
*
* This code follows the following naming conventions:
*
* char              ch_pmod_value
* char (array)      s_pmod_s_string[16]
* float             f_pmod_value
* int32_t           n_pmod_value
* int32_t (array)   an_pmod_value[16]
* int16_t           w_pmod_value
* int16_t (array)   aw_pmod_value[16]
* uint16_t          uw_pmod_value
* uint16_t (array)  auw_pmod_value[16]
* uint8_t           uch_pmod_value
* uint8_t (array)   auch_pmod_buffer[16]
* uint32_t          un_pmod_value
* int32_t *         pn_pmod_value
*
* ------------------------------------------------------------------------- */
/*******************************************************************************
* Copyright (C) 2016 Maxim Integrated Products, Inc., All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL MAXIM INTEGRATED BE LIABLE FOR ANY CLAIM, DAMAGES
* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* Except as contained in this notice, the name of Maxim Integrated
* Products, Inc. shall not be used except as stated in the Maxim Integrated
* Products, Inc. Branding Policy.
*
* The mere transfer of this software does not imply any licenses
* of trade secrets, proprietary technology, copyrights, patents,
* trademarks, maskwork rights, or any other form of intellectual
* property whatsoever. Maxim Integrated Products, Inc. retains all
* ownership rights.
*******************************************************************************
*/
/*!\mainpage Main Page
*
* \section intro_sec Introduction
*
* This is the code documentation for the MAXREFDES117# subsystem reference design.
* 
*  The Files page contains the File List page and the Globals page.
* 
*  The Globals page contains the Functions, Variables, and Macros sub-pages.
*
* \image html MAXREFDES117_Block_Diagram.png "MAXREFDES117# System Block Diagram"
* 
* \image html MAXREFDES117_firmware_Flowchart.png "MAXREFDES117# Firmware Flowchart"
*
*/
#include <Arduino.h>
#include "algorithm.h"
#include "max30102.h"//if Adafruit Flora development board is chosen, include NeoPixel library and define an NeoPixel object
#if defined(ARDUINO_AVR_FLORA8)
#include "adafruit_neopixel.h"
#define BRIGHTNESS_DIVISOR 8  //to lower the max brightness of the neopixel LED
Adafruit_NeoPixel LED = Adafruit_NeoPixel(1, 8, NEO_GRB + NEO_KHZ800);
#endif#define MAX_BRIGHTNESS 255#if defined(ARDUINO_AVR_UNO)
//Arduino Uno doesn't have enough SRAM to store 100 samples of IR led data and red led data in 32-bit format
//To solve this problem, 16-bit MSB of the sampled data will be truncated.  Samples become 16-bit data.
uint16_t aun_ir_buffer[100]; //infrared LED sensor data
uint16_t aun_red_buffer[100];  //red LED sensor data
#else
uint32_t aun_ir_buffer[100]; //infrared LED sensor data
uint32_t aun_red_buffer[100];  //red LED sensor data
#endif
int32_t n_ir_buffer_length; //data length
int32_t n_spo2;  //SPO2 value
int8_t ch_spo2_valid;  //indicator to show if the SPO2 calculation is valid
int32_t n_heart_rate; //heart rate value
int8_t  ch_hr_valid;  //indicator to show if the heart rate calculation is valid
uint8_t uch_dummy;// the setup routine runs once when you press reset:
void setup() {#if defined(ARDUINO_AVR_LILYPAD_USB)    pinMode(13, OUTPUT);  //LED output pin on Lilypad
#endif#if defined(ARDUINO_AVR_FLORA8)//Initialize the LEDLED.begin();LED.show();
#endifmaxim_max30102_reset(); //resets the MAX30102// initialize serial communication at 115200 bits per second:Serial.begin(9600);pinMode(10, INPUT);  //pin D10 connects to the interrupt output pin of the MAX30102delay(1000);maxim_max30102_read_reg(REG_INTR_STATUS_1,&uch_dummy);  //Reads/clears the interrupt status registerwhile(Serial.available()==0)  //wait until user presses a key{Serial.write(27);       // ESC commandSerial.print(F("[2J"));    // clear screen command
#if defined(ARDUINO_AVR_LILYPAD_USB)    Serial.println(F("Lilypad"));
#endif
#if defined(ARDUINO_AVR_FLORA8)Serial.println(F("Adafruit Flora"));
#endifSerial.println(F("Press any key to start conversion"));delay(1000);}uch_dummy=Serial.read();maxim_max30102_init();  //initialize the MAX30102
}// the loop routine runs over and over again forever:
void loop() {uint32_t un_min, un_max, un_prev_data, un_brightness;  //variables to calculate the on-board LED brightness that reflects the heartbeatsint32_t i;float f_temp;un_brightness=0;un_min=0x3FFFF;un_max=0;n_ir_buffer_length=100;  //buffer length of 100 stores 4 seconds of samples running at 25sps//read the first 100 samples, and determine the signal rangefor(i=0;i<n_ir_buffer_length;i++){while(digitalRead(10)==1);  //wait until the interrupt pin assertsmaxim_max30102_read_fifo((aun_red_buffer+i), (aun_ir_buffer+i));  //read from MAX30102 FIFOif(un_min>aun_red_buffer[i])un_min=aun_red_buffer[i];  //update signal minif(un_max<aun_red_buffer[i])un_max=aun_red_buffer[i];  //update signal max//Serial.print(F("red="));//Serial.print(aun_red_buffer[i], DEC);//Serial.print(F(", ir="));//Serial.println(aun_ir_buffer[i], DEC);}un_prev_data=aun_red_buffer[i];//calculate heart rate and SpO2 after first 100 samples (first 4 seconds of samples)maxim_heart_rate_and_oxygen_saturation(aun_ir_buffer, n_ir_buffer_length, aun_red_buffer, &n_spo2, &ch_spo2_valid, &n_heart_rate, &ch_hr_valid); //Continuously taking samples from MAX30102.  Heart rate and SpO2 are calculated every 1 secondwhile(1){i=0;un_min=0x3FFFF;un_max=0;//dumping the first 25 sets of samples in the memory and shift the last 75 sets of samples to the topfor(i=25;i<100;i++){aun_red_buffer[i-25]=aun_red_buffer[i];aun_ir_buffer[i-25]=aun_ir_buffer[i];//update the signal min and maxif(un_min>aun_red_buffer[i])un_min=aun_red_buffer[i];if(un_max<aun_red_buffer[i])un_max=aun_red_buffer[i];}//take 25 sets of samples before calculating the heart rate.for(i=75;i<100;i++){un_prev_data=aun_red_buffer[i-1];while(digitalRead(10)==1);digitalWrite(9, !digitalRead(9));maxim_max30102_read_fifo((aun_red_buffer+i), (aun_ir_buffer+i));//calculate the brightness of the LEDif(aun_red_buffer[i]>un_prev_data){f_temp=aun_red_buffer[i]-un_prev_data;f_temp/=(un_max-un_min);f_temp*=MAX_BRIGHTNESS;f_temp=un_brightness-f_temp;if(f_temp<0)un_brightness=0;elseun_brightness=(int)f_temp;}else{f_temp=un_prev_data-aun_red_buffer[i];f_temp/=(un_max-un_min);f_temp*=MAX_BRIGHTNESS;un_brightness+=(int)f_temp;if(un_brightness>MAX_BRIGHTNESS)un_brightness=MAX_BRIGHTNESS;}
#if defined(ARDUINO_AVR_LILYPAD_USB)  analogWrite(13, un_brightness);
#endif#if defined(ARDUINO_AVR_FLORA8)LED.setPixelColor(0, un_brightness/BRIGHTNESS_DIVISOR, 0, 0);LED.show();
#endif//send samples and calculation result to terminal program through UARTSerial.print(F("red="));Serial.println(aun_red_buffer[i], DEC);Serial.print(F("ir="));Serial.println(aun_ir_buffer[i], DEC);Serial.print(F("HR="));Serial.println(n_heart_rate, DEC);Serial.print(F("HRvalid="));Serial.println(ch_hr_valid, DEC);Serial.print(F("SPO2="));Serial.println(n_spo2, DEC);Serial.print(F("SPO2Valid="));Serial.println(ch_spo2_valid, DEC);}maxim_heart_rate_and_oxygen_saturation(aun_ir_buffer, n_ir_buffer_length, aun_red_buffer, &n_spo2, &ch_spo2_valid, &n_heart_rate, &ch_hr_valid); }
}

实际使用的时候，整个程序是可以使用的，但是存在一些需要提高的点，比如基线漂移影响严重，比如心律计算严重失真（虽然事实上不是特别用得上），都是需要在接下来的工作中进行改进的地方。

【串口接收到发送来的血氧信号的Matlab绘图：基线漂移明显】