问题
I have a simple sonar arduino project so that it prints the distance every second. I have implemented an android app using UsbSerial to communicate with my arduino. So far so good, I am able to receive data and the data I receive is correct, but the problem is that the values are sometimes not properly sent. Here is the sample output I receive:
data: 7
data: 1
data:
data: 71
and here is the code that generates output:
private UsbSerialInterface.UsbReadCallback mCallback = new UsbSerialInterface.UsbReadCallback() {
@Override
public void onReceivedData(byte[] arg0)
{
try {
String data = new String(arg0, "UTF-8");
System.out.println("data: " + data);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
};
So in my opinion there is 2 problems here:
- Lines 1 & 2 must be just one line with the value of
71
- Line 3 should not exists as my application is listening
onReceivedData
and arduino always send something.
Any help would be much appreciated.
回答1:
I have found a solution for the issue. by reading this link I noticed that I need to do some manipulation on the data I receive in the onReceivedData
method.
So I changed the mCallBack
as follow:
private UsbSerialInterface.UsbReadCallback mCallback = new UsbSerialInterface.UsbReadCallback() {
@Override
public void onReceivedData(byte[] arg0)
{
if(arg0!= null && arg0.length > 0){
if (isStartByte(arg0[0])) {
printData();
clearBytes();
}
appendBytes(arg0);
}
}
};
and here is the other methods I added:
private void clearBytes(){
buffer=new byte[8];
bufferSize = 0;
}
private void appendBytes(byte[] buf){
System.arraycopy(buf, 0, buffer, bufferSize, buf.length);
bufferSize += buf.length;
}
private void printData() {
if (bufferSize == 0) {
return;
}
byte[] buf = new byte[bufferSize];
System.arraycopy(buffer, 0, buf, 0, bufferSize);
String data = null;
try {
data = new String(buf, "UTF-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
if (null != data && !data.isEmpty()) {
System.out.println("data: " + data);
}
}
public boolean isStartByte(byte firstChar){
return firstChar=='A';
}
And also I modified the Arduino code and added character A
to the beginning of the serial output.
This solves the issue, however I think this is not the best practice. I think the UsbSerial library should provide better output handling( or maybe I am wrong and this is the nature of working with serial communication ).
来源:https://stackoverflow.com/questions/41421035/android-app-not-synchronized-with-arduino-serial-communication