Question

I followed this tutorial to get started using Android host api with an Arduino board. I am using the Arduino Uno. I am able to transmit data and turn on a LED on the Arduino board and I can receive feedback from the Arduino board. I am trying to write to my Android device over the USB connection from the Arduino board like so:

 Serial.print("Test");

I am receiving the Arduino data on the Android side like this:

byte[] buffer = new byte[10];
int bytes;
//try-catch statements omitted for simplicity
bytes = mUsbConnection.bulkTransfer(mUsbEndpointIn, buffer, buffer.length, 0);

Every once and awhile the data will be intact but more often than not, what I receive from the Arduino is a garbled mix of those letters from my original message(t,e,s, and t). Many times only 1 or 2 letters are displayed. If anyone could point me in the right direction or share some similar experience I would be appreciative. Thanks.

Edit

When I print out the data into Logcat, there are multiple copies of the data. For example, if I receive "ste" from Arduino, it will be printed out 2-5 times in Logcat.

Answer 1

I think I found something that works at least temporarily:

public void run(){

        int i = 0;

        byte[] buffer = new byte[4];
        byte[] finalBuffer = new byte[8];
        byte[] sendBuffer = new byte[8];

        int bytes = 0;

        while(true){
            try{

                bytes = mUsbConnection.bulkTransfer(mUsbEndpointIn, buffer, buffer.length, 0);

                if (bytes == EXIT_CMD) { 
                    return;
                } 

                if (bytes > 0){

                    byte[] temporaryBuffer = new byte[bytes];

                    System.arraycopy(buffer, 0, temporaryBuffer, 0, bytes);

                    System.arraycopy(temporaryBuffer, 0, finalBuffer, i, bytes);

                    i += bytes;

                    java.util.Arrays.fill(buffer, (byte) 0);
                }

                //Dollar sign terminates string to indicate end of line
                if (finalBuffer[7] == 36){

                    i = 0;

                    System.arraycopy(finalBuffer, 0, sendBuffer, 0, sendBuffer.length); 

                    messageHandler.obtainMessage(UsbHostTestActivity.ARDUINO_MESSAGE, 
                            sendBuffer.length, -1, sendBuffer).sendToTarget();

                    java.util.Arrays.fill(finalBuffer, (byte) 0);
                }

I had to send strings that were 8 characters exactly from Arduino and they had to end with a dollar sign($) in order to indicate the end of the line, but the data being passed to my message handler always seemed to be correct. It’s not the most robust solution but maybe someone can modify it to make it better or take another approach? Please let me know!