Help with serial port Bluetooth module

Using Arduino Networking, Protocols, and Devices
1

Hi folks,

I have bluetooth module attached to arduino and connected (via bluetooth) to my android phone.

But the messages are intermittent splitted.

Arduino:

void loop(){
   Serial1.write("123456");
   delay(300);
}

Android log:

Received (6 bytes): 123456
Received (1 bytes): 1
Received (5 bytes): 23456
Received (1 bytes): 1
Received (5 bytes): 23456
and so on...

It's normal?
I should do a packaging method or something else? Maybe set messages with start and end mark..?

Maybe is a dumb question.. sorry, I'm a beginner.

thanks in advance!

2

Hi
On Android side did you test it with some proven terminal like BlueTerm ot SenaBterm ?
Is your Android version known for good serial port profile handling ?
If you stay under 57600 bauds no reason loose bytes in such short messages if Android appication is good.

3

Serial.write() is meant for sending individual bytes, not strings of characters. With nothing to indicate what constitutes a packet within a stream of data, the receiver is just guessing.

In this case, the Android application guessed wrong.

4

Thanks PaulS and al1fch.
After a 1 minute thinking.. I've found a solution.

I have a thread to listen bluetooth stream... but this thread don't have sleep time. It's so fast to listen arduino. :blush:

Maybe isn't a perfect solution, because still data are broken, however much less (~10%)

I'm using 9600 baud rate. My Android 2.2.
I've tested with BlueTerm too with same results.

Soon I will post here the source code.

thanks

5

Adding a sleep to the listener is a bandaid, and a poor one at that. Notice that when we communicate we use punctuation to tell when a sentence (a packet) ends and spaces to tell when a word ends (another kind of packet.

WhatissohardaboutdoingthesamethinginyourserialcommunicationItcompletelyeliminatestheconfusionorambiguityaboutwhatconstitutesapacket.

6 
Serial1.write("123456");

I'm really surprised that works at all - I thought "write" took a single "byte" argument.

7

From Print.h:

    virtual void write(uint8_t) = 0;
    virtual void write(const char *str);
    virtual void write(const uint8_t *buffer, size_t size);

So, yes, there is an overload that takes a string.