将USB键盘数据从字节数组转换为字符串USB4Java

Question

I am reading a USB Keyboard (QR Code scanner) input using usb4java.

My code snippet looks like this:

byte[] data = new byte[16];
UsbPipe usbPipe = usbEndpoint.getUsbPipe();
if (usbPipe != null) {
    if (!usbPipe.isOpen()) {
        usbPipe.open();
    }
    if (usbPipe.isOpen()) {
        UsbIrp usbIrp = usbPipe.createUsbIrp();
        usbIrp.setData(data);

I have two questions:

1] On pressing A, byte array data is 2,0,0,0,0,0,0,0,2,0,4,0,0,0,0,0
On pressing AB, byte aray data is 2,0,0,0,0,0,0,0,2,0,4,0,0,0,0,0,2,0,5,0,0,0,0,0

How to convert it into character in java? ie get A or AB after conversion.

2] Currently, I am passing fixed size of byte array in above code snippet. For example, if I am expecting 1 char, I am passing 16 as size of byte array, for 2 characters 24 as size and so on. Is there any other elegant solution for making it dynamic?

PS: My byte array converter snippet:

StringBuffer sb = new StringBuffer();
for (byte b : data) {
    sb.append(b);
    sb.append(",");
}
String byteString = sb.toString();
return byteString;

Thanks for any help

EDIT 1: Full source code here: http://tpcg.io/zt3WfM

Answer 1

Based on the documentation the format should be:

22 00 04 00 00 00 00 00

Offset  Size    Description
0       Byte    Modifier keys status.
1       Byte    Reserved field.
2       Byte    Keypress #1.
3       Byte    Keypress #2.
4       Byte    Keypress #3.
5       Byte    Keypress #4.
6       Byte    Keypress #5.
7       Byte    Keypress #6. 

Based on the ASCII codes

// 'A' is 0x65
byte codeA = 0x04;     // The code for A key
cahr a = 0x61 + codeA ;
byte codeX = 0x1B;     // The code for X key
char x = 0x61 + code; // x == 'X'

System.out.println(a);
System.out.println(x);

Or you can use a Map(0x04, 'A')