There are few of us out here that have noticed a problem when appending to a file using the example from this tutorial...
https://arduinobasics.blogspot.com/2015/05/ch376s-usb-readwrite-module.html
Around every 512th byte written, the file closes and the data written will be truncated. The program does not clearly state that the response from command (0x2D) is the actual number of bytes written. I was sending 36 characters and getting a response of 0x24 for most of my lines. Then every few minutes, I would see a response of 9 after sending the 36 characters...??? And when you looked at the log file, it would look like:
1,2,3,4,5,6.00,08/30/2018,15:51:22
1,2,3,4,5,6.00,08/30/2018,15:51:32
1,2,3,4,5,6.00,08/30/2018,15:51:42
1,2,3,4,5,6.00,08/30/2018,15:51:52
1,2,3,4,5,6.00,08/30/2018,15:52:02
1,2,3,4,5,6.00,08/30/2018,15:52:12
1,2,3,4,5,6.00,08/30/2018,15:52:22
1,2,3,4,5,6.00,08/30/2018,15:52:32
1,2,3,4,5,6.00,08/30/2018,15:52:42
1,2,3,4,5,6.00,08/30/2018,15:52:52
1,2,3,4,5,6.00,08/30/2018,15:53:02
1,2,3,4,5,6.00,08/30/2018,15:53:12
1,2,3,4,51,2,3,4,5,6.00,08/30/2018,15:53:32
1,2,3,4,5,6.00,08/30/2018,15:53:42
1,2,3,4,5,6.00,08/30/2018,15:53:52
1,2,3,4,5,6.00,08/30/2018,15:54:02
To fix this problem I changed fileWrite to a function that returns the actual number of bytes written. I capture the response from the 0x2D command and return that value. I appendFile, I then compare the returned value to data.length(). If it is smaller, I rerun the appendFile routine after modifying "data" to only resend the truncated portion. Here is the original example from that tutorial with my mods.
I wanted to attach the entire example but it went beyond the 9000 character limit so here are the highlights....
/* ===============================================================
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.
=================================================================
//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.
byte numWr = fileWrite(data); //Write data to the end of the file and return num bytes written
fileClose(0x01); //Close the file using 0x01 - which means to update the size of the file on close.
if (numWr < data.length()){//not all bytes were written, some 512 byte barrier broken...???
//resend the lost data...
delay(100);
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.
data = data.substring(numWr); //remove the written data and write the truncated portion
fileWrite(data);
fileClose(0x01);
}
}
//fileWrite=======================================================================================
//are the commands used to write to the file
byte fileWrite(String data){
byte numByteWr = 0;
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
}
numByteWr = USB.read();
Serial.print("Write code.. (number bytes written) and 14 : ");
Serial.print(numByteWr); // code is number of bytes written to disk
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
}
}
return(numByteWr);
}
I did not modify the library as I did not want to use the library so I could manipulate some of the routines for my nefarious purposes...
Luke
