We are developping an app that uses Bluetooth library to communicate with an Arduino in bluetooth via an HC-05 module. We made a dummy configuration to test the delay without any computation from eather the Arduino or the app and we have a huge delay of about 1 second between a request and an answer...
Protocol looks easy : Android send byte -2 and if byte received is -2, Arduino send -6, -9 and Android answer again and again.
Android Code :
h = new Handler() {
public void handleMessage(android.os.Message msg) {
switch (msg.what) {
case RECIEVE_MESSAGE: // if receive massage
byte[] readBuf = (byte[]) msg.obj;
for(int i=0;i < readBuf.length;i++)
{
if((int) readBuf[i] != 0) {
txtArduino.append(String.valueOf((int) readBuf[i]) + ", ");
}
}
byte[] msg = {-2};
mConnectedThread.writeByte(msg);
break;
}
};
};
Arduino Code :
const int receveidBuffLen = 8*4;
void setup() {
Serial.begin(115200);
}
void loop() {
if (Serial.available() > 0)
{
byte buff[receveidBuffLen];
Serial.readBytes(buff, receveidBuffLen);
for(int i=0; i < receveidBuffLen;i++)
{
if(buff[i] == (byte) -2) // 254
{
byte message[2] = {(byte) -6, (byte) -9};
Serial.write(message, 2);
Serial.flush();
}
}
}
delay(3);
}
Does anyone know where the delay comes from?
We changed the HC05 baudrate (from 9600 to 115 200) : nothing happened. We changed HC05 with another : nothing happened. We used the Blue2Serial library (Bluetooth as SPP) before and delay was the same... We used another controler (ESP8266) and delay still was 1 second...
Looks like this string is an issue:
Serial.readBytes(buff, receveidBuffLen);
Where receveidBuffLen is 32.
Although you get single byte at a time, you're trying to read 32 of them. Of course, if there are no more bytes, the code will be stuck until timeout.
Furthermore, after bytes is read, you never check how many bytes were actually read, but do scan whole the array from bottom to top:
for(int i=0; i < receveidBuffLen;i++)
instead, you have to do something like this:
int bytesAvailable = Serial.available();
if (bytesAvailable > 0)
{
byte buff[receveidBuffLen];
int bytesToRead = (bytesAvailable < receveidBuffLen) ? bytesAvailable : receveidBuffLen;
// Read no more than the buffer size, but not more than available
int bytesActuallyRead = Serial.readBytes(buff, bytesToRead);
for(int i=0; i < bytesActuallyRead;i++)
...
There are a couple problems with the code that might cause delays:
delay function at end of loop - This will slow down the processing that the Ardunio can keep up with
Calling Serial.flush() - This will block the processing loop() until the internal TX serial buffer is empty. That means the Arduino is blocked and new RX data can pile up, slowing the response time.
Calling Serial.readBytes() - You should focus on the smallest unit of data and process that each loop() iteration. If you are trying to deal with multiple message per loop, that will slow now the loop time causing a delay.
You can try to implement a SerialEvent pattern on the Arduino. We will only read one byte at a time from the serial buffer, keeping the processing that the loop() function has todo to a bare minimum. If we receive the -2 byte we will mark a flag. If the flag is marked the loop() function will call the Serial.write() function but will not block for the data to transmit. Here is a quick example.
bool sendMessage = false;
byte message[2] = {(byte) -6, (byte) -9};
void loop()
{
if (sendMessage == true)
{
Serial.write(message, 2);
sendMessage = false;
}
}
/*
SerialEvent occurs whenever a new data comes in the hardware serial RX. This
routine is run between each time loop() runs, so using delay inside loop can
delay response. Multiple bytes of data may be available.
*/
void serialEvent()
{
while (Serial.available())
{
// get the new byte:
byte inChar = ((byte) Serial.read());
if (inChar == ((byte) -2))
{
sendMessage = true;
}
}
}
We just find some solutions by ourselves and want to share them :
Initial situation : 1050 ms for an answer. Alls solutions are independent and done with the initial situation.
Remove Serial.flush() : 1022 ms.
Add a simple Serial.setTimeout(100) in Arduino Code : 135 ms. (Oh man!)
Add a simple timeout to inputStream of 100ms in Android : 95 ms.
Which solution is the best, we can't say but it works now...
Related
I have a usb device which have a button.
And I want to an android app to catch a signal of the button.
I found inferface and endpoint number of the button.
It had seemed to perform ordinarily at galaxy S3 and galaxy note.
But later, I found that it has delay at other phones.
I was able to receive instant responses about 10% of the time; usually there was a 2-second delay, with some cases where the whole response was lost.
Although I couldn't figure out the exact reason, I realized that the phones that had response delays were those with kernel version 3.4 or later.
Here is the code that I used initially.
if(mConnection != null){
mConnection.claimInterface(mInterfaces.get(0), true);
final UsbEndpoint endpoint = mInterfaces.get(0).getEndpoint(0);
Thread getSignalThread = new Thread(new Runnable() {
#Override
public synchronized void run() {
byte[] buffer = new byte[8];
final ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
while(mConnection!=null){
int len = mConnection.bulkTransfer(endpoint, buffer, buffer.length, 0);
if( len>=0 ){
// do my own code
}
}
}
});
getSignalThread.setPriority(Thread.MAX_PRIORITY);
getSignalThread.start();
}
edit timeout
when the timeout was set to 50ms, I wasn't able to receive responses most of the time. When the timeout was 500ms, I was able to initially get some delayed-responses; however, I lost all responses after several tries with this setting.
Using UsbRequest
In addition to using the bulktransfer method, I also tried using UsbRequest and below is the code that I used.
#Override
public synchronized void run() {
byte[] buffer = new byte[8];
final ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
UsbRequest inRequest = new UsbRequest();
inRequest.initialize(mConnection, endpoint);
while(mConnection!=null){
inRequest.queue( byteBuffer , buffer.length);
if( mConnection.requestWait() == inRequest ){
// do my own code
}
}
}
However, the same kind of delay happened even after using UsbRequest.
Using libusb
I also tried using libusb_interrupt_transfer from an open source library called libusb.
However this also produced the same type of delay that I had when using UsbDeviceConnection.
unsigned char data_bt[8] = { 0, };
uint32_t out[2];
int transfered = 0;
while (devh_usb != NULL) {
libusb_interrupt_transfer(devh_usb, 0x83, data_bt, 8, &transfered, 0);
memcpy(out, data_bt, 8);
if (out[0] == PUSH) {
LOGI("button pushed!!!");
memset(data_bt, 0, 8);
//(env)->CallVoidMethod( thiz, mid);
}
}
After looking into the part where libusb_interrupt_transfer is processed libusb, I was able to figure out the general steps of interrupt_transfer:
1. make a transfer object of type interrupt
2. make a urb object that points to the transfer object
3. submit the urb object to the device's fd
4. detect any changes in the fd object via urb object
5. read urb through ioctl
steps 3, 4, 5 are the steps regarding file i/o.
I was able to find out that at step 4 the program waits for the button press before moving onto the next step.
Therefore I tried changing poll to epoll in order to check if the poll function was causing the delay; unfortunately nothing changed.
I also tried setting the timeout of the poll function to 500ms and making it always get values of the fd through ioctl but only found out that the value changed 2~3 seconds after pressing the button.
So in conclusion I feel that there is a delay in the process of updating the value of the fd after pressing the button. If there is anyone who could help me with this issue, please let me know. Thank you.
Thanks for reading
I am trying to send more than 33 bytes using simple loops, Is anybody has idea how to send more than 20 bytes data over android ble.
if(!mConnected) return;
for (int i = 0; i<str.length;i++) {
if(str[i] == str[str.length -1]){
val = str[i]+"\n";
}else {
val = str[i] + "_";
}
System.out.println(val);
mBluetoothLeService.WriteValue(val);
}
Sending more than 20 bytes via BLE is easily achievable by splitting your data into 20 byte packets and implementing a short delay (i.e. using sleep()) between sending each packet.
Here's a short snippet of code from a project I'm working on that takes data in the form of byte[] and splits it into an array of the same, ( byte[][] ), in 20 byte chunks, and then sends it to another method that transmits each packet one by one.
int chunksize = 20;
byte[][] packets = new byte[packetsToSend][chunksize];
int packetsToSend = (int) Math.ceil( byteCount / chunksize);
for(int i = 0; i < packets.length; i++) {
packets[i] = Arrays.copyOfRange(source,start, start + chunksize);
start += chunksize;
}
sendSplitPackets(packets);
Here are two other very good explanations of how to achieve this:
(Stackoverflow) Android: Sending data >20 bytes by BLE
(Nordic Semi) Dealing Large Data Packets Through BLE
You can send more than 20 bytes of data without breaking into chunks and including a delay. Every characteristics you are trying to write has an MTU value assigned. It's number of bytes you can write in one time.
During the connection MTU values are exchanged and you can write those many bytes at a time. You can increase the mtu value on the server side (Max 512 bytes) and send that much bytes in one go.
For Android, you might want to request mtu manually after connecting with the server using
requestMtu(int mtu)
This is return true or false based on the mtu value you send. It will give a callback to onMtuChanged where Android device and server negotiate the maximum possible MTU value.
onMtuChanged (BluetoothGatt gatt, int mtu, int status)
and you can set MTU value in this function and can send more than 20 bytes in one go.
Some embedded bluetooth LE implementations limit the size of a characteristic to be 20 bytes. I know that the Laird BL600 series does this. This is limitation of the Laird module, even though the BLE spec calls for the max length to be longer. Other embedded BLE solutions have similar limits. I suspect this is the limitation that you are encountering.
Instead of using sleep for every chunk, i just found a better and efficient way for my application to send more than 20 bit data.
The packets will be send after onCharacteristicWrite() triggered. i just found out this method will be triggered automatically after peripheral device (BluetoothGattServer) sends a sendResponse() method.
firstly we have to transform the packet data into chunk with this function:
public void sendData(byte [] data){
int chunksize = 20; //20 byte chunk
packetSize = (int) Math.ceil( data.length / (double)chunksize); //make this variable public so we can access it on the other function
//this is use as header, so peripheral device know ho much packet will be received.
characteristicData.setValue(packetSize.toString().getBytes());
mGatt.writeCharacteristic(characteristicData);
mGatt.executeReliableWrite();
packets = new byte[packetSize][chunksize];
packetInteration =0;
Integer start = 0;
for(int i = 0; i < packets.length; i++) {
int end = start+chunksize;
if(end>data.length){end = data.length;}
packets[i] = Arrays.copyOfRange(data,start, end);
start += chunksize;
}
after our data ready, so i put my iteration on this function:
#Override
public void onCharacteristicWrite(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic, int status) {
if(packetInteration<packetSize){
characteristicData.setValue(packets[packetInteration]);
mGatt.writeCharacteristic(characteristicData);
packetInteration++;
}
}
I'm trying to communicate between Arduino Mega Adk (ADK 2011) and android device.
Something goes ok, but something goes completely wrong.
Transfer data from Android to Arduino via acc.read from Arduino side works fine.
But when i try to send some bytes from Arduino to Android - something strange happens.
First of all here is Arduino sketch:
#include <Max3421e_constants.h>
#include <Max3421e.h>
#include <Usb.h>
#include <AndroidAccessory.h>
#define COMMAND_LED 0x2
#define TARGET_PIN_18 0x12
#define TARGET_PIN_19 0x13
#define V_ON 0x1
#define V_OFF 0x0
#define PIN_18 18
#define PIN_19 19
#define INPUT_PIN 30
AndroidAccessory acc("Google, Inc.",
"DemoKit",
"Ololo device board",
"1.0",
"http://www.android.com",
"0000000012345678");
byte rcvmsg[3];
byte sndmsg[3];
int buttonState = 0;
void setup();
void loop();
void led_setup(){
pinMode(PIN_18, OUTPUT);
pinMode(PIN_19, OUTPUT);
pinMode(INPUT_PIN, INPUT);
}
void setup()
{
Serial.begin(115200);
Serial.print("\r\nStart");
led_setup();
acc.powerOn();
}
void loop()
{
if (acc.isConnected()) {
buttonState = digitalRead(INPUT_PIN);
if (buttonState == 1){
sndmsg[0] = 0x2;
sndmsg[1] = 0x1;
sndmsg[2] = 0x1;
int len = acc.write(sndmsg, 3);
digitalWrite(PIN_19, HIGH);
}
else {
//Nothing here for test
}
}
//usefull test for button
buttonState = digitalRead(INPUT_PIN);
if (buttonState == 1){
digitalWrite(PIN_19, HIGH);
}
else {
digitalWrite(PIN_19, LOW);
}
}
Ok. When acc.write() is executed it takes up to ~1 second to transfer data to android. And this time doesn't depend on number of bytes in sndmsg. Only if i execute acc.write(sndmsg,0) (sending 0 bytes) - everything goes fast.
That is a little bit disturbing. I've tried to change board to another one but have got the same result.
Any advices? may be that is a common bug, but there is no such much information in web.
UPD:
Wrote some very simple code, that only sends 3 bytes via acc.write.
here it is:
#include <Max3421e_constants.h>
#include <Max3421e.h>
#include <Usb.h>
#include <AndroidAccessory.h>
AndroidAccessory acc("Google, Inc.",
"DemoKit",
"Demokit board",
"1.0",
"http://www.android.com",
"0000000012345678");
byte msg[3];
unsigned long time;
void setup();
void loop();
void led_setup(){
}
void setup()
{
Serial.begin(115200);
Serial.print("\r\nStart");
acc.powerOn();
}
void loop()
{
if (acc.isConnected()) {
Serial.print("\r\nis Connected");
msg[0] = 0x1;
msg[1] = 0x1;
msg[2] = 0x1;
//Serial.print("\r\nSending");
time = millis();
Serial.print ("\r\nBefore write\r\n");
Serial.print (time);
acc.write(msg, 3);
time = millis();
Serial.print("\r\nAfter write: \r\n");
Serial.print (time);
//delay(500);
}
}
And it's debug output is:
is Connected
Before write
6983
After write:
10958
is Connected
Before write
10958
After write:
14491
is Connected
and so on. So on some reasons acc.write takes a lot of time and there is no data in the android app.
New UPD (19.01.2015):
Today i've performed some experiments. Here are results.
First, i've looked into AndroidAccessory.cpp and found write function:
int AndroidAccessory::write(void *buff, int len)
{
usb.outTransfer(1, out, len, (char *)buff);
return len;
}
Ok, then i looked into usb host shield library and found there usb.cpp with outTransfer fucntion, that returns error code if ouccured and 0x00 if everything is ok.
So i modified write function to return an error code instead of lenght, like this:
int AndroidAccessory::write(void *buff, int len)
{
byte rcode;
rcode = usb.outTransfer(1, out, len, (char *)buff);
return int(rcode);
}
and recived "4" as result.
According to MAX3421Econstants.h it is hrNAK (0x04) error code.
Any ideas? Looks like accessory does not recive NAKs from Android and write fails as a result.
Situation update:
Did some research. There is a hell of NAK's when accessory is connected. Here is dump from usb connector:
i found the solution. And it is very simple - i didn't setup communication with accessory correctly.
This is not an Arduino problem. Arduino works fine.
It is just how android interacts with android accessory.
So, results:
When AndroidAccessory is plugged to Android and Android haven't setup
communication with the accessory yet, Android OS will send a lot of
USB NAKs to the accessory and this is normal.
You must be careful
during setuping communication with the accessory. If you make some
mistakes, you can receive same situation: Probably possible to write
to the accessory, but accessory isn't possible to write to the
android.
If UsbManager opens accessory correctly, it stops sending
NAKs and starts recieve data from arduino.
It is a little bit strange for me, because it was really hard to found a problem: i have an application, written according to this manual: http://developer.android.com/guide/topics/connectivity/usb/accessory.html But, because i'm not very familiar with android, it seems that i've done some mistakes and receive strange behavior:
i was able to write to arduino
i was able to retrive information about arduino as android accessory
it was possible to ask for permissions
but when arduino tries to write to android, it recievs a lot of NAKs
So i decided to rewrite program in more simple way, just with one function and tried to do it in right way. And after some debugging it finally started to work as i want.
So thank everyone, who spend time for reading this.
Bonus: dump of normal packet, ended with EOP not NAK
UPD 26.01.2015:
I found problem and it was in my android code.
here is explanation:
Android developer's manual said that function, which set up communication with accessory must start it's own thread in which all communications with input and output streams are held. Smth like this:
private void openAccessory() {
Log.d(TAG, "openAccessory: " + accessory);
mFileDescriptor = mUsbManager.openAccessory(mAccessory);
if (mFileDescriptor != null) {
FileDescriptor fd = mFileDescriptor.getFileDescriptor();
mInputStream = new FileInputStream(fd);
mOutputStream = new FileOutputStream(fd);
Thread thread = new Thread(null, this, "AccessoryThread");
thread.start();
}
}
I really messed this thing up. Forgot about creating new thread in openAccessory function and tried to do it in different place. And recieve a hell of NAK's. Then i've changed my code and add some debug-like run() function like this:
public void run() {
final byte[] buffer = new byte[16384];
int ret = 0;
int i = 0;
while (i<50) {
try {
ret = mInputStream.read(buffer);
i++;
Thread.sleep(500);
} catch (IOException e) {
break;
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
And until this run method exists (while i < 50) android reads arduino correctly. And when thread ends up (i > 50) - Arduino starts to readout Error Code 4 (NAK) from Android.
That's all folks.
Since my problem is close to this one, I haven been looing at feedbacks from this possible solution : Reading on a NetworkStream = 100% CPU usage but I fail to find the solution I need.
Much like in this other question, I want to use something else than an infinite while loop.
More precisely, I am using Xamarin to build Android application in Visual Studio. Since I need a Bluetooth service I am using a Stream to read and send data.
Reading data from Stream.InputStrem is where I have a problem : is there some sort of a blocking call to wait for data to be available without using a while (true) loop ?
I tried :
Begin/End Read
Task.Run and await
Here is a code sample:
public byte[] RetrieveDataFromStream()
{
List<byte> packet = new List<byte>();
int readBytes = 0;
while (_inputStream.CanRead && _inputStream.IsDataAvailable() && readBytes < 1024 && _state == STATE_CONNECTED)
{
try
{
byte[] buffer = new byte[1];
readBytes = _inputStream.Read(buffer, 0, buffer.Length);
packet.Add(buffer[0]);
}
catch (Java.IO.IOException e)
{
return null;
}
}
return packet.ToArray();
}
I call this method from a while loop.
This loop will check until this method returns something else than NULL in which case I will process the data accordingly.
As soon as there is data to be processed, the CPU usage gets low, way lower than if there was no data to process.
I know why my CPU usage is high : the loop will check as often as possible if there is something to read. On the plus side, there is close to no delay when recieving data, but no, that's not a viable solution.
Any ideas to change this ?
# UPDATE 1
As per Marc Gravell's idea, here is what I would like to understand and try :
byte buffer = new byte[4096];
while (_inputStream.CanRead
&& (readBytes = _inputStream.Read(buffer, 0, buffer.Length)) > 0
&& _state == STATE_CONNECTED)
{
for(int i = 0 ; i < readBytes; i++)
packet.Add(buffer[i]);
// or better: some kind of packet.AddRange(buffer, 0, readBytes)
}
How do you call this code snippet ?
Two questions :
If there is nothing to read, then the while condition will be
dismissed : what to do next ?
Once you're done reading, what do you do next ? What do you do to catch any new incoming packets ?
Here are some explanations that should help :
The android device is connected, via bluetooth, to another device that sends data. It will always send a pre-designed packet with a specified size (1024)
That device can stream the data continuously for some time but can also stop at any time for a long period too. How to deal with such behavior ?
An immediate fix would be:
don't read one byte at a time
don't create a new buffer per-byte
don't sit in a hot loop when there is no data available
For example:
byte buffer = new byte[4096];
while (_inputStream.CanRead
&& (readBytes = _inputStream.Read(buffer, 0, buffer.Length)) > 0
&& _state == STATE_CONNECTED)
{
for(int i = 0 ; i < readBytes; i++)
packet.Add(buffer[i]);
// or better: some kind of packet.AddRange(buffer, 0, readBytes)
}
Note that the use of readBytes in the original while check looked somewhat... confused; I've replaced it with a "while we don't get an EOF" check; feel free to add your own logic.
So I am facing a problem from a while now . Any suggestion would be good.
First I used my code to receive data from arduino , then I used the bluetoothChat and changed the uuid , I can pair , everything is good , but if I send an entire string from arduino to android I get only parts of that string.
If I use bluetooth terminal from google play everything is ok, and on the description it says it is made from the bluetooth Chat sample .
Code Arduino
#include <SoftwareSerial.h>
SoftwareSerial mySerial(10, 9); //RX,TX
long int i = 0;
void setup(){
mySerial.begin(9600);
}
void loop(){
mySerial.print("This is a message n. ");
mySerial.println(i);
i++;
delay(100);
}
Android code : Bluetooth Chat Sample
Exemple of message received on Android:
Message to be sent!
So first messages I think are waiting while the module is paired .
because every time I get .
is is a message n. 466
This is a message n.467
.
. ( here I get correct messages )
.
This is a message n.470
message n. 495
.
.
and after the first messages I get messages like
ssage n.534
t
essage n.m
essage n.
535
( I neved again get an entire message )
Handler :
h = new Handler() {
public void handleMessage(Message msg) {
switch (msg.what) {
case RECIEVE_MESSAGE: // if receive massage
byte[] readBuf = (byte[]) msg.obj;
String strIncom = new String(readBuf, 0, msg.arg1); // create string from bytes array
sb.append(strIncom); // append string
int endOfLineIndex = sb.indexOf("\r\n"); // determine the end-of-line
if (endOfLineIndex > 0) { // if end-of-line,
String sbprint = sb.substring(0, endOfLineIndex); // extract string
sb.delete(0, sb.length()); // and clear
Log.d("Arduino", "Mesaj:"+ sbprint.toString());
}
Log.d("Arduino", "...Mesaj:"+ sb.toString() + " Byte:" + msg.arg1 + "...");
break;
}
};
};
Listener to InputStream
public void run() {
byte[] buffer = new byte[256]; // buffer store for the stream
int bytes; // bytes returned from read()
// Keep listening to the InputStream until an exception occurs
while (true) {
try {
// Read from the InputStream
bytes = mmInStream.read(buffer); // Get number of bytes and message in "buffer"
h.obtainMessage(RECIEVE_MESSAGE, bytes, -1, buffer).sendToTarget(); // Send to message queue Handler
} catch (IOException e) {
break;
}
}
}
note you are using a software emulation of serial port, hence timing is not as good as it would be with a hardware UART.
It is likely one or both of the following two possible issues:
1) the start and stop bit are not properly timed, causing back to back bytes. Which occur when a string is set, rather then pecking in keys one at a time.
The solution would be to space out each key.
2) baud rates do not match with in tolerance. Either SLOWING DOWN or SPEEDING UP the baud rate on both the HC05 and Arduino will better match the timing.
I would also recommend ensuring your library is SoftwareSerial, states that it is NewSoftSerial. It has many issues fixed. It was implemented in to the Arduino IDE 1.0.+ core libraries, so if you have recent IDE you should have it.