Develop Reference

HC-06 Bluetooth to Android - Receiving Random Symbols

I wanted to send values from a light sensor, using an HC-06. I have everything connected properly. I used MIT App Inventor and the image shows how I connect to the Bluetooth module, and how do I show the data.
Arduino Code
int analogInPin = A0;
int sensorValue = 0;
void setup() {
Serial.begin(9600);
}
void loop() {
sensorValue = analogRead(analogInPin);
Serial.println(sensorValue);
delay(100);
}
Phone
I already searched for several solutions but none worked. I have the baud rate at 9600 (the same as the Bluetooth module).

Send String + Int data through Bluetooth Arduino

I am new to Arduino and I have been working on a problem that has been troubling me for a few days.
I have an Arduino Uno and an HC-05 Bluetooth module.
Basically I want to send String and Int data together through Bluetooth.
CODE
#include <SoftwareSerial.h>
SoftwareSerial BTSerial(10, 11); // RX | TX
void setup(void) {
// Arduino setup
Serial.begin(9600);
// setting the baud rate of bluetooth
BTSerial.begin(38400); // HC-05 default speed in AT command more
}
void loop(void) {
int num = 123;
BTSerial.write("#"); // Works
BTSerial.write(num); // works
BTSerial.write(String(num) + "#");
// Error: no matching function for call to 'SoftwareSerial::write(StringSumHelper&)'
}
Also the result string should have '#' character at last.
According to the Arduino Website, it has 2 functions.
- Serial.write(val)
- Serial.write(str)
Any help appreciated.
Thank you.

write is for sending raw bytes. You want to use Serial.print instead.

if you want to send String from an another device to arduino, your code sould be like this:
#include <SoftwareSerial.h>
SoftwareSerial BT(3, 4);
String bt = "";
void setup() {
BT.begin(9600);
Serial.begin(9600);
}
void loop() {
if(BT.available()){
bt = BT.readString();
}
Serial.println(bt);
while(!BT.available());
}
the above code, waits for your bluetooth module to recieve any data and reads a String from it and prints it in Serial.
In order to send Int, you can read a String and parse it to Int.

Arduino Mega ADK strange acc.write() behavior (huge delay) NAK issue seemd to be confirmed. Android generates NAK's as a result of acc.write

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.

control a servo with android and arduino

I'm trying to control a servo with an android phone and an arduino via bluetooth but the data in the arduino is received as a char, and the arduino doesn't know when all the data is received and the servo don't move properly. The arduino code is this:
#include
Servo myservo;
char val; // variable to receive data from the serial port
int ledpin = 13; // LED connected to pin 48 (on-board LED)
void setup() {
pinMode(ledpin, OUTPUT); // pin 48 (on-board LED) as OUTPUT
Serial.begin(9600); // start serial communication at 9600bps
myservo.attach(9);
}
void loop() {
if( Serial.available() ) // if data is available to read
{
val = Serial.read(); // read it and store it in 'val'
}
if( val - 0 >= 0 && val - 0 <= 180){
}
// Serial.print("Recibido");
delay(100); // wait 100ms for next reading
}
What can I do to get the correct value from "val" to control the servo?

You can send multiple chars if you need them. Simple store each new char into an array and program your android program to send a specific byte that indicates the ending of the val reading.
Checking this "ending" byte each time you perform a read from serial will tell you if this char is to store or to convert the previous stored chars into an integer or whatever data type you need it.
Than simply converting that array will tell you the correct val.

Bluetooth serial communication issue between Arduino and Android

I have written an application for Android in Java using Eclipse to send data to an Arduino via Bluetooth.
The devices seem to be connected okay, but when I send data from the Android to the Arduino the receive (RX) light on the Arduino board doesn't light up.
Can someone help?
#define arduinoRx 2
#define arduinoTx 3
int gelen_veri;
int LedCikis = 8;
SoftwareSerial bluetooth(arduinoRx, arduinoTx);
void setup() {
bluetooth.begin(9600);
}
void loop() {
if (bluetooth.available() > 0) {
gelen_veri=bluetooth.read();
switch (gelen_veri) {
case 'A' :
digitalWrite(LedCikis, HIGH);
break;
case 'K' :
digitalWrite(LedCikis, LOW);
break;
default:
break;
}
}
}

Use the serial rx/tx pins instead of SoftwareSerial. I've had problems with SoftwareSerial in the past and my HC-05 bluetooth module.