Bluetooth master slave communication is not working well

Projects Programming
1

Hello guys,

I use a reed sensor to get speed on bicycle, this speed is sending from Arduino Mega via HC 05 to Arduino Uno via next HC 05 as master slave. Pairing is done well because Arduinos can change the information but Arduino slave reads wrong these information.

I want slave Arduino will control the pwm pin according to the speed that receives. Faster speed = 100% pwm, low or no speed = 0% pwm.

Current function: Arduino gets random values, sometime pwm is 100%, sometime 0%. I don't know why. Can you help me please? Thank you very much. Scheme is attached.

I would also need to reset the pwm if the value of speed is for example 3 seconds the same... But it also does not work...

Master

float start, finished;
float elapsed, time;
float circMetric=2.093; // wheel circumference (in meters)
float circImperial; // using 1 kilometer = 0.621371192 miles
int speedk, speedm;

float AuraPWM;

void setup() {
Serial.begin(9600);
circImperial=circMetric*.62137;

attachInterrupt(digitalPinToInterrupt(2), speedCalc, RISING);

start=millis();
}

void speedCalc()
{
//Function called by the interrupt

if((millis()-start)>100) // 100 millisec debounce
{
//calculate elapsed
elapsed=millis()-start;

//reset start
start=millis();

//calculate speed in km/h
speedk=(3600*circMetric)/elapsed;

//calculate speed in mph
speedm=(3600*circImperial)/elapsed;
}
}

void loop() {
Serial.println(speedk);
Serial.write(speedk);
delay(100);

AuraPWM = speedk;

}

Slave
#define Aura 3
int state = 0; // Vyctena hodnota z bluetooth
int OldState = 0;
int8_t AuraPWM = 0;
long unsigned OldMillis = 0;
long unsigned OldMillis2 = 0;
void setup() {
pinMode(Aura, OUTPUT);
Serial.begin(9600);
}
void loop() {
if (millis() - OldMillis > 500) {
OldMillis = millis();
if (state - OldState == 0) {
state = 0;
}
OldState = state;
}
if (Serial.available() > 0)
{
state = Serial.read();
AuraPWM = state * 10;
if (state != OldState) {
OldMillis = millis();
OldState = state;
}
}
if (millis() - OldMillis2 > 1000) {
OldMillis2 = millis();
Serial.println(state);
analogWrite(Aura, state);
}
}

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20190521_091619.jpg1161×2064 689 KB

2

via next HC 05 as master slave.

The HC-05 is either a master or a slave.

float elapsed, time;

Time passes in integral amounts.

circImperial=circMetric*.62137;

Getyourspacekeyfixed.

void loop() {
Serial.println(speedk);
Serial.write(speedk);

WTF? You either want to send the value as a string or as binary, NOT both.

The write() method takes a byte, NOT an int.

state = Serial.read();

Read returns an int ONLY so that the high order byte can indicate an error. Only one byte contains valid data. If you are sending the int as a byte, in binary, this will contain the byte (with the high order byte lost). If you are sending the data as string, you need to collect the bytes (characters) in a string (a NULL terminated array of chars), until the end of packet marker arrives, and then use atoi() to convert the string to an int.

3

PaulS:
The HC-05 is either a master or a slave.

float elapsed, time;

Time passes in integral amounts.

circImperial=circMetric*.62137;

Getyourspacekeyfixed.

Hello, thank you for fast answer. I am lost with that. A problem for me is I hurry on that to try one working principle. Can you repair this code please?

Thank you very much

4

Can you repair this code please?

No, because I don't know what you want to do.

If you want to send binary data, you need to learn how to send a two-byte int as two bytes, and how to read the two bytes and re-assemble the int.

If you want to send ASCII data, Robin2 has a tutorial (it's a sticky) on how to send and receive serial data with start and end of packet markers.