Android HID USB how to send hexadecimal data with bulkTransfer or controlTransfer?

Question

I'm trying to send hexadecimal data to connected USB HID device from my Nexus 7, but Android SDK method can work only with byte[] buffer.

How can I send hexadeсimal data that originates as decimal String values with bulkTransfer or controlTransfer?

message[0]= 0;
message[1]= 166;
message[2]= 2;
message[3]= 252;
message[4]= 255;

SDK Methods:

bulkTransfer(UsbEndpoint endpoint, byte[] buffer, int length, int timeout)

controlTransfer(int requestType, int request, int value, int index, byte[] buffer, int length, int timeout)

like this: http://pure-basic.narod.ru/article/pickit2.html, PC application with the device works good.

OutBuffer(0)=0
OutBuffer(1)=$A6 ; EXECUTE_SCRIPT
OutBuffer(2)=2
OutBuffer(3)=$FC ; _VDD_GND_OFF
OutBuffer(4)=$FF ; _VDD_ON

UPDATE - ANSWER

private void sendData() {
  //byte b = (byte) 129; // (byte) 0x81 Also work
  int status = connection.bulkTransfer(endPointWrite, toByte(129), 1, 250);
}

private static byte toByte(int c) {
  return (byte) (c <= 0x7f ? c : ((c % 0x80) - 0x80));
}

// for received data from USB HID device
private static int toInt(byte b) {
  return (int) b & 0xFF;
}

My application on Google play - USB HID TERMINAL

Answer 1

This depends on what the target of the message buffer will be.

Since you are getting decimal values from a String you can use the Integer.parseInt method with a radix of 10, then cast to a byte:

byte message[] = new byte[] { (byte)java.lang.Integer.parseInt("0", 10),
            (byte)java.lang.Integer.parseInt("166", 10),
            (byte)java.lang.Integer.parseInt("2", 10),
            (byte)java.lang.Integer.parseInt("252", 10),
            (byte)java.lang.Integer.parseInt("255", 10)
};

If you simply want to send the data over the bulk pipe then you would send it as follows:

bulkTransfer(outEndpoint, message, message.length, 1000);

Control requests typically target some function on the USB device itself and is vendor defined. If you need to send the buffer as a control request you would send it as follows:

controlTransfer(USB_DIR_OUT, VENDOR_DEFINED_REQUEST, VENDOR_DEFINED_VALUE, USB_INTERFACE_INDEX, message, message.length, 1000);