JURNAL ARDUINO: 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


/* ===============================================================
      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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JURNAL ARDUINO

Thursday, May 7, 2015

CH376S USB Read/Write module

Parts Required:

Remove the Jumper

Fritzing Sketch

Arduino Sketch

Serial Commands

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