7 May 2015

CH376S USB Read/Write module

Have you ever wondered if there was a way to store and retrieve data from a USB stick with an Arduino UNO? Most people choose SD cards to store their project data, but you may be surprised there IS a way!
IC Station have a nice little module which allows you store and retrieve your Arduino (or other MCU) project data to a USB stick.
 
I am not too sure why USB storage is not widely used in Arduino projects? These modules are not expensive, they have been around for quite a while, and are relatively simple to use. You do not need any libraries to get them to work, however, I must say that documentation for this module is not that easy to find. This site and this document proved to be very useful in my endevour to get this module working, and I hope my tutorial below will help you get started and bridge some of the information gaps.
 
The "CH376S USB read/write module" has a CH376S chip onboard which does most of the hard work for you. All you have to do is send the module some commands from the Arduino and the CH376S chip will do the rest. You can communicate with the module in three different ways:

  • Parallel communication
  • SPI communication
  • and Serial (UART) communication.

This project will show you the connections and code for the Serial (UART) communication method only.


 

Parts Required:

Remove the Jumper

When the CH376S USB module arrives in it's package, it will have a jumper between the TXD pin and GND. You will need to remove this jumper to make the necessary connections between the Arduino UNO and the CH376S USB module.


 

Fritzing Sketch

Please note, that the Arduino Sketch makes use of the Arduino UNO's onboard LED on digital pin 13. The Fritzing sketch below shows an LED + 300 ohm resistor on a breadboard. This is optional. The LED is not a necessary component of CH376S module communication.

Also be aware that the CH376S USB module has an onboard LED just above the TXD and GND pins near the USB port. This LED will only turn on providing the CH376S module is in USB mode AND a USB device has been inserted into the USB port. Both conditions must be met before the module's onboard LED will illuminate. You will not see the LED turn on just by powering the board.
 
The wire diagram below is the correct setup for Serial communication between an Arduino UNO and the CH376S module. If you wish to use SPI or Parallel communication, you will need to refer to the datasheet.


 
 

Arduino Sketch


 
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/* ===============================================================
      Project: CH376S USB Read/Write Module testing ground
       Author: Scott C
      Created: 1st May 2015
  Arduino IDE: 1.6.2
      Website: http://arduinobasics.blogspot.com/p/arduino-basics-projects-page.html
  Description: This project will allow you to perform many of the functions available on the CH376S module.
               Checking connection to the module, putting the module into USB mode, resetting the module, 
               reading, writing, appending text to files on the USB stick. This is very useful alternative to
               SD card modules, plus it doesn't need any libraries.
================================================================== */

#include <SoftwareSerial.h>

byte computerByte;           //used to store data coming from the computer
byte USB_Byte;               //used to store data coming from the USB stick
int LED = 13;                //the LED is connected to digital pin 13 
int timeOut = 2000;          //TimeOut is 2 seconds. This is the amount of time you wish to wait for a response from the CH376S module.
String wrData = "What is the meaning of life ?";     //We will write this data to a newly created file.
String wrData2 = "42";                                   //We will append this data to an already existing file.

SoftwareSerial USB(10, 11);                           // Digital pin 10 on Arduino (RX) connects to TXD on the CH376S module
                                                      // Digital pin 11 on Arduino (TX) connects to RXD on the CH376S module
                                                      // GND on Arduino to GND on CH376S module
                                                      // 5V on Arduino to 5V on CH376S module
//==============================================================================================================================================
void setup() {
  Serial.begin(9600);                                 // Setup serial communication with the computer (using a baud rate of 9600 on serial monitor)
  USB.begin(9600);                                    // Setup serial communication with the CH376S module (using the default baud rate of 9600)
  pinMode(LED,OUTPUT);                                // Define digital pin 13 as an OUTPUT pin - so that we can use it with an LED
  digitalWrite(LED,LOW);                              // Turn off the LED
}

//================================================================================================================================================
void loop() {
  if(Serial.available()){
    computerByte = Serial.read();                      //read any incoming bytes from the Serial monitor, and store this byte in the variable called computerByte
    if(computerByte==49){               //1            //If you send the number 1 from the serial monitor, the arduino will read it as digital number 49. Google "ascii table" for more info.
      printCommandHeader("COMMAND1: CHECK CONNECTION");
      checkConnection(0x01);                           // Check for successful connection and communication with the CH376S module.
    } 
    if(computerByte==50){               //2
     printCommandHeader("COMMAND2: set_USB_Mode");
      set_USB_Mode(0x06);                              // Code used to enable read/write communication and monitoring of the USB stick
    }
    if(computerByte==51){               //3
      printCommandHeader("COMMAND3: resetALL");
      resetALL();                                      // Reset the USB device
    }
    if(computerByte==52){               //4
      printCommandHeader("COMMAND4: Create and Write to File : TEST4.TXT");
      writeFile("TEST4.TXT", wrData);                  // Create a file called TEST4.TXT and then Write the contents of wrData to this file
    }
    if(computerByte==53){               //5
      printCommandHeader("COMMAND5: Read File: TEST4.TXT");
      readFile("TEST4.TXT");                           // Read the contents of this file on the USB disk, and display contents in the Serial Monitor
    }
    if(computerByte==54){               //6
      printCommandHeader("COMMAND6: Append data to file: TEST4.TXT");
      appendFile("TEST4.TXT", wrData2);                // Append data to the end of the file.
    }
    if(computerByte==55){               //7
      printCommandHeader("COMMAND7: Delete File: TEST4.TXT");
      fileDelete("TEST4.TXT");                         // Delete the file named TEST4.TXT
    }
    if(computerByte==56){               //8
      printCommandHeader("COMMAND8: Read File: TEST2.TXT");
      readFile("TEST2.TXT");                           // Read the contents of the TEST2.TXT file on the USB disk, and display contents in the Serial Monitor
    }
    if(computerByte==57){               //9
      printCommandHeader("COMMAND9: Read File: TEST3.TXT");
      readFile("TEST3.TXT");                           // Read the contents of the TEST3.TXT file on the USB disk, and display contents in the Serial Monitor
    }
  }
  
  if(USB.available()){                                 // This is here to capture any unexpected data transmitted by the CH376S module
    Serial.print("CH376S has just sent this code:");
    Serial.println(USB.read(), HEX);
  }
}

//END OF LOOP FUNCTION ========================================================================================================================================

//print Command header
void printCommandHeader(String header){
   Serial.println("======================");
   Serial.println("");
   Serial.println(header);
   Serial.println("----------------------");
}

//checkConnection==================================================================================
//This function is used to check for successful communication with the CH376S module. This is not dependant of the presence of a USB stick.
//Send any value between 0 to 255, and the CH376S module will return a number = 255 - value. 
void checkConnection(byte value){
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x06);
  USB.write(value);
  
  if(waitForResponse("checking connection")){       //wait for a response from the CH376S. If CH376S responds, it will be true. If it times out, it will be false.
    if(getResponseFromUSB()==(255-value)){
       Serial.println(">Connection to CH376S was successful.");
       blinkLED();                               //blink the LED for 1 second if the connection was successful
    } else {
      Serial.print(">Connection to CH376S - FAILED.");
    }
  }
}

//set_USB_Mode=====================================================================================
//Make sure that the USB is inserted when using 0x06 as the value in this specific code sequence
void set_USB_Mode (byte value){
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x15);
  USB.write(value);
  
  delay(20);
  
  if(USB.available()){
    USB_Byte=USB.read();
    //Check to see if the command has been successfully transmitted and acknowledged.
    if(USB_Byte==0x51){                                   // If true - the CH376S has acknowledged the command.
        Serial.println("set_USB_Mode command acknowledged"); //The CH376S will now check and monitor the USB port
        USB_Byte = USB.read();
        
        //Check to see if the USB stick is connected or not.
        if(USB_Byte==0x15){                               // If true - there is a USB stick connected
          Serial.println("USB is present");
          blinkLED();                                     // If the process was successful, then turn the LED on for 1 second 
        } else {
          Serial.print("USB Not present. Error code:");   // If the USB is not connected - it should return an Error code = FFH
          Serial.print(USB_Byte, HEX);
          Serial.println("H");
        }
        
    } else {
        Serial.print("CH3765 error!   Error code:");
        Serial.print(USB_Byte, HEX);
        Serial.println("H");
    }   
  }
  delay(20);
}

//resetALL=========================================================================================
//This will perform a hardware reset of the CH376S module - which usually takes about 35 msecs =====
void resetALL(){
    USB.write(0x57);
    USB.write(0xAB);
    USB.write(0x05);
    Serial.println("The CH376S module has been reset !");
    delay(200);
}

//readFile=====================================================================================
//This will send a series of commands to read data from a specific file (defined by fileName)
void readFile(String fileName){
  resetALL();                     //Reset the module
  set_USB_Mode(0x06);             //Set to USB Mode
  diskConnectionStatus();         //Check that communication with the USB device is possible
  USBdiskMount();                 //Prepare the USB for reading/writing - you need to mount the USB disk for proper read/write operations.
  setFileName(fileName);          //Set File name
  fileOpen();                     //Open the file for reading
  int fs = getFileSize();         //Get the size of the file
  fileRead();                     //***** Send the command to read the file ***
  fileClose(0x00);                //Close the file
}

//writeFile========================================================================================
//is used to create a new file and then write data to that file. "fileName" is a variable used to hold the name of the file (e.g TEST.TXT). "data" should not be greater than 255 bytes long. 
void writeFile(String fileName, String data){
  resetALL();                     //Reset the module
  set_USB_Mode(0x06);             //Set to USB Mode
  diskConnectionStatus();         //Check that communication with the USB device is possible
  USBdiskMount();                 //Prepare the USB for reading/writing - you need to mount the USB disk for proper read/write operations.
  setFileName(fileName);          //Set File name
  if(fileCreate()){               //Try to create a new file. If file creation is successful
    fileWrite(data);              //write data to the file.
  } else {
    Serial.println("File could not be created, or it already exists");
  }
  fileClose(0x01);
}

//appendFile()====================================================================================
//is used to write data to the end of the file, without erasing the contents of the file.
void appendFile(String fileName, String data){
    resetALL();                     //Reset the module
    set_USB_Mode(0x06);             //Set to USB Mode
    diskConnectionStatus();         //Check that communication with the USB device is possible
    USBdiskMount();                 //Prepare the USB for reading/writing - you need to mount the USB disk for proper read/write operations.
    setFileName(fileName);          //Set File name
    fileOpen();                     //Open the file
    filePointer(false);             //filePointer(false) is to set the pointer at the end of the file.  filePointer(true) will set the pointer to the beginning.
    fileWrite(data);                //Write data to the end of the file
    fileClose(0x01);                //Close the file using 0x01 - which means to update the size of the file on close. 
}
  
//setFileName======================================================================================
//This sets the name of the file to work with
void setFileName(String fileName){
  Serial.print("Setting filename to:");
  Serial.println(fileName);
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x2F);
  USB.write(0x2F);         // Every filename must have this byte to indicate the start of the file name.
  USB.print(fileName);     // "fileName" is a variable that holds the name of the file.  eg. TEST.TXT
  USB.write((byte)0x00);   // you need to cast as a byte - otherwise it will not compile.  The null byte indicates the end of the file name.
  delay(20);
}

//diskConnectionStatus================================================================================
//Check the disk connection status
void diskConnectionStatus(){
  Serial.println("Checking USB disk connection status");
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x30);

  if(waitForResponse("Connecting to USB disk")){       //wait for a response from the CH376S. If CH376S responds, it will be true. If it times out, it will be false.
    if(getResponseFromUSB()==0x14){               //CH376S will send 0x14 if this command was successful
       Serial.println(">Connection to USB OK");
    } else {
      Serial.print(">Connection to USB - FAILED.");
    }
  }
}

//USBdiskMount========================================================================================
//initialise the USB disk and check that it is ready - this process is required if you want to find the manufacturing information of the USB disk
void USBdiskMount(){
  Serial.println("Mounting USB disk");
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x31);

  if(waitForResponse("mounting USB disk")){       //wait for a response from the CH376S. If CH376S responds, it will be true. If it times out, it will be false.
    if(getResponseFromUSB()==0x14){               //CH376S will send 0x14 if this command was successful
       Serial.println(">USB Mounted - OK");
    } else {
      Serial.print(">Failed to Mount USB disk.");
    }
  }
}

//fileOpen========================================================================================
//opens the file for reading or writing
void fileOpen(){
  Serial.println("Opening file.");
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x32);
  if(waitForResponse("file Open")){                 //wait for a response from the CH376S. If CH376S responds, it will be true. If it times out, it will be false.
    if(getResponseFromUSB()==0x14){                 //CH376S will send 0x14 if this command was successful  
       Serial.println(">File opened successfully.");
    } else {
      Serial.print(">Failed to open file.");
    }
  }
}

//setByteRead=====================================================================================
//This function is required if you want to read data from the file. 
boolean setByteRead(byte numBytes){
  boolean bytesToRead=false;
  int timeCounter = 0;
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x3A);
  USB.write((byte)numBytes);   //tells the CH376S how many bytes to read at a time
  USB.write((byte)0x00);
  if(waitForResponse("setByteRead")){       //wait for a response from the CH376S. If CH376S responds, it will be true. If it times out, it will be false.
    if(getResponseFromUSB()==0x1D){         //read the CH376S message. If equal to 0x1D, data is present, so return true. Will return 0x14 if no data is present.
      bytesToRead=true;
    }
  }
  return(bytesToRead);
} 

//getFileSize()===================================================================================
//writes the file size to the serial Monitor.
int getFileSize(){
  int fileSize=0;
  Serial.println("Getting File Size");
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x0C);
  USB.write(0x68);
  delay(100);
  Serial.print("FileSize =");
  if(USB.available()){
    fileSize = fileSize + USB.read();
  } 
  if(USB.available()){
    fileSize = fileSize + (USB.read()*255);
  } 
  if(USB.available()){
    fileSize = fileSize + (USB.read()*255*255);
  } 
  if(USB.available()){
    fileSize = fileSize + (USB.read()*255*255*255);
  }     
  Serial.println(fileSize);
  delay(10);
  return(fileSize);
}


//fileRead========================================================================================
//read the contents of the file
void fileRead(){
  Serial.println("Reading file:");
  byte firstByte = 0x00;                     //Variable to hold the firstByte from every transmission.  Can be used as a checkSum if required.
  byte numBytes = 0x40;                      //The maximum value is 0x40  =  64 bytes
 
  while(setByteRead(numBytes)){              //This tells the CH376S module how many bytes to read on the next reading step. In this example, we will read 0x10 bytes at a time. Returns true if there are bytes to read, false if there are no more bytes to read.
    USB.write(0x57);
    USB.write(0xAB);
    USB.write(0x27);                          //Command to read ALL of the bytes (allocated by setByteRead(x))
    if(waitForResponse("reading data")){      //Wait for the CH376S module to return data. TimeOut will return false. If data is being transmitted, it will return true.
        firstByte=USB.read();                 //Read the first byte
        while(USB.available()){
          Serial.write(USB.read());           //Send the data from the USB disk to the Serial monitor
          delay(1);                           //This delay is necessary for successful Serial transmission
        }
    }
    if(!continueRead()){                       //prepares the module for further reading. If false, stop reading.
      break;                                   //You need the continueRead() method if the data to be read from the USB device is greater than numBytes.
    }
  }
  Serial.println();
  Serial.println("NO MORE DATA");
}

//fileWrite=======================================================================================
//are the commands used to write to the file
void fileWrite(String data){
  Serial.println("Writing to file:");
  byte dataLength = (byte) data.length();         // This variable holds the length of the data to be written (in bytes)
  Serial.println(data);
  Serial.print("Data Length:");
  Serial.println(dataLength);
  delay(100);
  // This set of commands tells the CH376S module how many bytes to expect from the Arduino.  (defined by the "dataLength" variable)
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x3C);
  USB.write((byte) dataLength);
  USB.write((byte) 0x00);
  if(waitForResponse("setting data Length")){      // Wait for an acknowledgement from the CH376S module before trying to send data to it
    if(getResponseFromUSB()==0x1E){                // 0x1E indicates that the USB device is in write mode.
      USB.write(0x57);
      USB.write(0xAB);
      USB.write(0x2D);
      USB.print(data);                             // write the data to the file
  
      if(waitForResponse("writing data to file")){   // wait for an acknowledgement from the CH376S module
      }
      Serial.print("Write code (normally FF and 14): ");
      Serial.print(USB.read(),HEX);                // code is normally 0xFF
      Serial.print(",");
      USB.write(0x57);
      USB.write(0xAB);
      USB.write(0x3D);                             // This is used to update the file size. Not sure if this is necessary for successful writing.
      if(waitForResponse("updating file size")){   // wait for an acknowledgement from the CH376S module
      }
      Serial.println(USB.read(),HEX);              //code is normally 0x14
    }
  }
}

//continueRead()==================================================================================
//continue to read the file : I could not get this function to work as intended.
boolean continueRead(){
  boolean readAgain = false;
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x3B);
  if(waitForResponse("continueRead")){       //wait for a response from the CH376S. If CH376S responds, it will be true. If it times out, it will be false.
     if(getResponseFromUSB()==0x14){         //CH376S will send 0x14 if this command was successful
       readAgain=true;
     }
  }
  return(readAgain);
} 

//fileCreate()========================================================================================
//the command sequence to create a file
boolean fileCreate(){
  boolean createdFile = false;
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x34);
  if(waitForResponse("creating file")){       //wait for a response from the CH376S. If file has been created successfully, it will return true.
     if(getResponseFromUSB()==0x14){          //CH376S will send 0x14 if this command was successful
       createdFile=true;
     }
  }
  return(createdFile);
}


//fileDelete()========================================================================================
//the command sequence to delete a file
void fileDelete(String fileName){
  setFileName(fileName);
  delay(20);
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x35);
  if(waitForResponse("deleting file")){       //wait for a response from the CH376S. If file has been created successfully, it will return true.
     if(getResponseFromUSB()==0x14){          //CH376S will send 0x14 if this command was successful
       Serial.println("Successfully deleted file");
     }
  }
}
  

//filePointer========================================================================================
//is used to set the file pointer position. true for beginning of file, false for the end of the file.
void filePointer(boolean fileBeginning){
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x39);
  if(fileBeginning){
    USB.write((byte)0x00);             //beginning of file
    USB.write((byte)0x00);
    USB.write((byte)0x00);
    USB.write((byte)0x00);
  } else {
    USB.write((byte)0xFF);             //end of file
    USB.write((byte)0xFF);
    USB.write((byte)0xFF);
    USB.write((byte)0xFF);
  }
  if(waitForResponse("setting file pointer")){       //wait for a response from the CH376S. 
     if(getResponseFromUSB()==0x14){                 //CH376S will send 0x14 if this command was successful
       Serial.println("Pointer successfully applied");
     }
  }
}


//fileClose=======================================================================================
//closes the file
void fileClose(byte closeCmd){
  Serial.println("Closing file:");
  USB.write(0x57);
  USB.write(0xAB);
  USB.write(0x36);
  USB.write((byte)closeCmd);                                // closeCmd = 0x00 = close without updating file Size, 0x01 = close and update file Size

  if(waitForResponse("closing file")){                      // wait for a response from the CH376S. 
     byte resp = getResponseFromUSB();
     if(resp==0x14){                                        // CH376S will send 0x14 if this command was successful
       Serial.println(">File closed successfully.");
     } else {
       Serial.print(">Failed to close file. Error code:");
       Serial.println(resp, HEX);
     }  
  }
}

//waitForResponse===================================================================================
//is used to wait for a response from USB. Returns true when bytes become available, false if it times out.
boolean waitForResponse(String errorMsg){
  boolean bytesAvailable = true;
  int counter=0;
  while(!USB.available()){     //wait for CH376S to verify command
    delay(1);
    counter++;
    if(counter>timeOut){
      Serial.print("TimeOut waiting for response: Error while: ");
      Serial.println(errorMsg);
      bytesAvailable = false;
      break;
    }
  }
  delay(1);
  return(bytesAvailable);
}

//getResponseFromUSB================================================================================
//is used to get any error codes or messages from the CH376S module (in response to certain commands)
byte getResponseFromUSB(){
  byte response = byte(0x00);
  if (USB.available()){
    response = USB.read();
  }
  return(response);
}



//blinkLED==========================================================================================
//Turn an LED on for 1 second
void blinkLED(){
  digitalWrite(LED, HIGH);
  delay(1000);
  digitalWrite(LED,LOW);
}


If you copy and paste this code directly into the Arduino IDE; you may get a warning like this when you compile the code:
 
   "Low memory available, stability problems may occur".
 
I managed to run the sketch without any issues, however, I did experience problems with some of the methods when I had made further memory hungry modifications. If you do encounter problems, I would recommend that you eliminate any methods which you do not plan to use, and perhaps reduce the number of Serial.print statements throughout the code. However, please note that some of the methods will not work unless the module is in the correct state, so be careful which methods you delete. For example, I found that I could get some simple functionality without the "USBdiskMount()" method. However, I could not read/write data beyond a certain length without this method.
 
Also please note, that some of the methods called within the reading and writing sequence do not need to be called every time. They can be called once in setup, while other methods within the sequence will need to be called every time. I grouped them all together for simplicity.


Serial Commands

Have a look at the following presentation for a summary of the Serial commands used in this tutorial:
 


 
 



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24 April 2015

Arduino Heart Rate Monitor


Project Description


Heart Rate Monitors are very popular at the moment.
There is something very appealing about watching the pattern of your own heart beat. And once you see it, there is an unstoppable urge to try and control it. This simple project will allow you to visualize your heart beat, and will calculate your heart rate. Keep reading to learn how to create your very own heart rate monitor.


 

Parts Required:


Fritzing Sketch


 

 
 
 

Grove Base Shield to Module Connections


 


 

Arduino Sketch


 
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/* =================================================================================================
      Project: Arduino Heart rate monitor
       Author: Scott C
      Created: 21st April 2015
  Arduino IDE: 1.6.2
      Website: http://arduinobasics.blogspot.com/p/arduino-basics-projects-page.html
  Description: This is a simple sketch that uses a Grove Ear-clip Heart Rate sensor attached to an Arduino UNO,
               which sends heart rate data to the computer via Serial communication. You can see the raw data
               using the Serial monitor on the Arduino IDE, however, this sketch was specifically
               designed to interface with the matching Processing sketch for a much nicer graphical display.
               NO LIBRARIES REQUIRED.
=================================================================================================== */

#define Heart 2                            //Attach the Grove Ear-clip sensor to digital pin 2.
#define LED 4                              //Attach an LED to digital pin 4

boolean beat = false;                      /* This "beat" variable is used to control the timing of the Serial communication
                                           so that data is only sent when there is a "change" in digital readings. */

//==SETUP==========================================================================================
void setup() {
  Serial.begin(9600);                     //Initialise serial communication
  pinMode(Heart, INPUT);                  //Set digital pin 2 (heart rate sensor pin) as an INPUT
  pinMode(LED, OUTPUT);                   //Set digital pin 4 (LED) to an OUTPUT
}


//==LOOP============================================================================================
void loop() {
  if(digitalRead(Heart)>0){               //The heart rate sensor will trigger HIGH when there is a heart beat
    if(!beat){                            //Only send data when it first discovers a heart beat - otherwise it will send a high value multiple times
      beat=true;                          //By changing the beat variable to true, it stops further transmissions of the high signal
      digitalWrite(LED, HIGH);            //Turn the LED on 
      Serial.println(1023);               //Send the high value to the computer via Serial communication.
    }
  } else {                                //If the reading is LOW, 
    if(beat){                             //and if this has just changed from HIGH to LOW (first low reading)
      beat=false;                         //change the beat variable to false (to stop multiple transmissions)
      digitalWrite(LED, LOW);             //Turn the LED off.
      Serial.println(0);                  //then send a low value to the computer via Serial communication.
    }
  }
}


 
 
 
 

Processing Sketch


 
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/* =================================================================================================
       Project: Arduino Heart rate monitor
        Author: Scott C
       Created: 21st April 2015
Processing IDE: 2.2.1
       Website: http://arduinobasics.blogspot.com/p/arduino-basics-projects-page.html
   Description: A Grove Ear-clip heart rate sensor allows an Arduino UNO to sense your pulse.
                The data obtained by the Arduino can then be sent to the computer via Serial communication
                which is then displayed graphically using this Processing sketch.
                
=================================================================================================== */

import processing.serial.*;                             // Import the serial library to allow Serial communication with the Arduino

int numOfRecs = 45;                                     //   numOfRecs: The number of rectangles to display across the screen
Rectangle[] myRecs = new Rectangle[numOfRecs];          //    myRecs[]: Is the array of Rectangles.  Rectangle is a custom class (programmed within this sketch)

Serial myPort;                                         
String comPortString="0";                              //comPortString: Is used to hold the string received from the Arduino
float arduinoValue = 0;                                 //arduinoValue: Is the float variable converted from comPortString
boolean beat = false;                                   //        beat: Used to control for multiple high/low signals coming from the Arduino

int totalTime = 0;                                      //   totalTime: Is the variable used to identify the total time between beats
int lastTime = 0;                                       //    lastTime: Is the variable used to remember when the last beat took place
int beatCounter = 0;                                    // beatCounter: Is used to keep track of the number of beats (in order to calculate the average BPM)
int totalBeats = 10;                                    //  totalBeats: Tells the computer that we want to calculate the average BPM using 10 beats.
int[] BPM = new int[totalBeats];                        //       BPM[]: Is the Beat Per Minute (BPM) array - to hold 10 BPM calculations
int sumBPM = 0;                                         //      sumBPM: Is used to sum the BPM[] array values, and is then used to calculate the average BPM.
int avgBPM = 0;                                         //      avgBPM: Is the variable used to hold the average BPM calculated value.

PFont f, f2;                                            //     f & f2 : Are font related variables. Used to store font properties. 


//==SETUP==============================================================================================
void setup(){
  size(displayWidth,displayHeight);                     // Set the size of the display to match the monitor width and height
  smooth();                                             // Draw all shapes with smooth edges.
  f = createFont("Arial",24);                           // Initialise the "f" font variable    - used for the "calibrating" text displayed at the beginning
  f2 = createFont("Arial",96);                          // Initialise the "f2" font variable   - used for the avgBPM display on screen
  
  for(int i=0; i<numOfRecs; i++){                       // Initialise the array of rectangles
    myRecs[i] = new Rectangle(i, numOfRecs);
  }
  
  for(int i=0; i<totalBeats; i++){                      // Initialise the BPM array
    BPM[i] = 0;
  }
  
  myPort = new Serial(this, Serial.list()[0], 9600);    // Start Serial communication with the Arduino using a baud rate of 9600
  myPort.bufferUntil('\n');                             // Trigger a SerialEvent on new line
}


//==DRAW==============================================================================================
void draw(){
  background(0);                                        // Set the background to BLACK (this clears the screen each time)
  drawRecs();                                           // Method call to draw the rectangles on the screen
  drawBPM();                                            // Method call to draw the avgBPM value to the top right of the screen
}


//==drawRecs==========================================================================================
void drawRecs(){                                        // This custom method will draw the rectangles on the screen                                
  myRecs[0].setSize(arduinoValue);                      // Set the first rectangle to match arduinoValue; any positive value will start the animation.
  for(int i=numOfRecs-1; i>0; i--){                     // The loop counts backwards for coding efficiency - and is used to draw all of the rectangles to screen
    myRecs[i].setMult(i);                               // setMulti creates the specific curve pattern. 
    myRecs[i].setRed(avgBPM);                           // The rectangles become more "Red" with higher avgBPM values
    myRecs[i].setSize(myRecs[i-1].getH());              // The current rectangle size is determined by the height of the rectangle immediately to it's left
    fill(myRecs[i].getR(),myRecs[i].getG(), myRecs[i].getB());                     // Set the colour of this rectangle
    rect(myRecs[i].getX(), myRecs[i].getY(), myRecs[i].getW(), myRecs[i].getH());  // Draw this rectangle
  }
}


//==drawBPM===========================================================================================
void drawBPM(){                                         // This custom method is used to calculate the avgBPM and draw it to screen.
  sumBPM = 0;                                           // Reset the sumBPM variable
  avgBPM = 0;                                           // Reset the avgBPM variable
  boolean calibrating = false;                          // calibrating: this boolean variable is used to control when the avgBPM is displayed to screen
  
  for(int i=1; i<totalBeats; i++){
    sumBPM = sumBPM + BPM[i-1];                         // Sum all of the BPM values in the BPM array.
    if(BPM[i-1]<1){                                     // If any BPM values are equal to 0, then set the calibrating variable to true. 
      calibrating = true;                               // This will be used later to display "calibrating" on the screen.
    }
  }
  avgBPM = sumBPM/(totalBeats-1);                       // Calculate the average BPM from all BPM values
                                                        
  fill(255);                                            // The text will be displayed as WHITE text
  if(calibrating){
    textFont(f);
    text("Calibrating", (4*width)/5, (height/5));      // If the calibrating variable is TRUE, then display the word "Calibrating" on screen
    fill(0);                                           // Change the fill and stroke to black (0) so that other text is "hidden" while calibrating variable is TRUE
    stroke(0);
  } else {
    textFont(f2);
    text(avgBPM, (4*width)/5, (height/5));             // If the calibrating variable is FALSE, then display the avgBPM variable on screen
    stroke(255);                                       // Change the stroke to white (255) to show the white line underlying the word BPM.
  }
  
   textFont(f);
   text("BPM", (82*width)/100, (height/11));           // This will display the underlined word "BPM" when calibrating variable is FALSE.
   line((80*width)/100, (height/10),(88*width)/100, (height/10));
   stroke(0);
}


//==serialEvent===========================================================================================
void serialEvent(Serial cPort){                        // This will be triggered every time a "new line" of data is received from the Arduino
 comPortString = cPort.readStringUntil('\n');          // Read this data into the comPortString variable.
 if(comPortString != null) {                           // If the comPortString variable is not NULL then
   comPortString=trim(comPortString);                  // trim any white space around the text.
   int i = int(map(Integer.parseInt(comPortString),1,1023,1,height));  // convert the string to an integer, and map the value so that the rectangle will fit within the screen.
   arduinoValue = float(i);                            // Convert the integer into a float value.
   if (!beat){
     if(arduinoValue>0){                               // When a beat is detected, the "trigger" method is called.
       trigger(millis());                              // millis() creates a timeStamp of when the beat occured.
       beat=true;                                      // The beat variable is changed to TRUE to register that a beat has been detected.
     }
   }
   if (arduinoValue<1){                                // When the Arduino value returns back to zero, we will need to change the beat status to FALSE.
     beat = false;
   }
 }
} 


//==trigger===========================================================================================
void trigger(int time){                                // This method is used to calculate the Beats per Minute (BPM) and to store the last 10 BPMs into the BPM[] array.
  totalTime = time - lastTime;                         // totalTime = the current beat time minus the last time there was a beat.
  lastTime = time;                                     // Set the lastTime variable to the current "time" for the next round of calculations.
  BPM[beatCounter] = 60000/totalTime;                  // Calculate BPM from the totalTime. 60000 = 1 minute.
  beatCounter++;                                       // Increment the beatCounter 
  if (beatCounter>totalBeats-1){                       // Reset the beatCounter when the total number of BPMs have been stored into the BPM[] array.
    beatCounter=0;                                     // This allows us to keep the last 10 BPM calculations at all times.
  }
}


//==sketchFullScreen==========================================================================================
boolean sketchFullScreen() {                           // This puts Processing into Full Screen Mode
 return true;
}


//==Rectangle CLASS==================================================================================*********
class Rectangle{
  float xPos, defaultY, yPos, myWidth, myHeight, myMultiplier;    // Variables used for drawing rectangles
  int blueVal, greenVal, redVal;                                  // Variables used for the rectangle colour
  
  Rectangle(int recNum, int nRecs){                               // The rectangles are constructed using two variables. The total number of rectangles to be displayed, and the identification of this rectangle (recNum)
    myWidth = displayWidth/nRecs;                                 // The width of the rectangle is determined by the screen width and the total number of rectangles.
    xPos = recNum * myWidth;                                      // The x Position of this rectangle is determined by the width of the rectangles (all same) and the rectangle identifier.
    defaultY=displayHeight/2;                                     // The default Y position of the rectangle is half way down the screen.
    yPos = defaultY;                                              // yPos is used to adjust the position of the rectangle as the size changes.
    myHeight = 1;                                                 // The height of the rectangle starts at 1 pixel
    myMultiplier = 1;                                             // The myMultiplier variable will be used to create the funnel shaped path for the rectangles.
    redVal = 0;                                                   // The red Value starts off being 0 - but changes with avgBPM. Higher avgBPM means higher redVal
    
    if (recNum>0){                                                // The blue Value progressively increases with every rectangle (moving to the right of the screen)
      blueVal = (recNum*255)/nRecs;
    } else {
      blueVal = 0;
    }
    greenVal = 255-blueVal;                                       // Initially, the green value is at the opposite end of the spectrum to the blue value.
  }
  
  void setSize(float newSize){                                    // This is used to set the new size of each rectangle 
    myHeight=newSize*myMultiplier;
    yPos=defaultY-(newSize/2);
  }
  
  void setMult(int i){                                            // The multiplier is a function of COS, which means that it varies from 1 to 0.
    myMultiplier = cos(radians(i));                               // You can try other functions to experience different effects.
  }
  
  void setRed(int r){
    redVal = int(constrain(map(float(r), 60, 100, 0, 255),0,255)); // setRed is used to change the redValue based on the "normal" value for resting BPM (60-100). 
    greenVal = 255 - redVal;                                       // When the avgBPM > 100, redVal will equal 255, and the greenVal will equal 0.
  }                                                                // When the avgBPM < 60, redVal will equal 0, and greenVal will equal 255.
  
  float  getX(){                                                   // get the x Position of the rectangle
    return xPos;
  }
 
  float getY(){                                                    // get the y Position of the rectangle
    return yPos;
  }
  
  float getW(){                                                    // get the width of the rectangle
    return myWidth;
  }
  
  float getH(){                                                    // get the height of the rectangle
    return myHeight;
  }
  
  float getM(){                                                    // get the Multiplier of the rectangle
    return myMultiplier;
  }
  
  int getB(){                                                      // get the "blue" component of the rectangle colour
    return blueVal;
  }
  
  int getR(){                                                      // get the "red" component of the rectangle colour
    return redVal;
  }
  
  int getG(){                                                      // get the "green" component of the rectangle colour
    return greenVal;
  }
}


 

Processing Code Discussion:


The Rectangle class was created to store relevant information about each rectangle. By using a custom class, we were able to design our rectangles any way we wanted. These rectangles have properties and methods which allow us to easily control their position, size and colour. By adding some smart functionality to each rectangle, we were able to get the rectangle to automatically position and colour itself based on key values.

The Serial library is used to allow communication with the Arduino. In this Processing sketch, the values obtained from the Arduino were converted to floats to allow easy calulations of the beats per minute (BPM). I am aware that I have over-engineered the serialEvent method somewhat, because the Arduino is only really sending two values. I didn't really need to convert the String. But I am happy with the end result, and it does the job I needed it to...


This project is quite simple. I designed it so that you could omit the Processing code if you wanted to. In that scenario, you would only be left with a blinking LED that blinks in time with your pulse. The Processing code takes this project to the next level. It provides a nice animation and calculates the beats per minute (BPM).
 
I hope you liked this tutorial. Please feel free to share it, comment or give it a plus one. If you didn't like it, I would still appreciate your constructive feedback.

 



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