I2c read from Slave

Using Arduino Programming Questions
#1

Hello, ist there anybody who can help me?

I’d like to reade 2 Values from 0-100 ( J1 and J2) from a Slave Device (Arduino Nano)
On The Master ( Arduino Uno) There is runnig following code:

#include <Wire.h>

void setup()
{
Wire.begin();
Serial.begin(9600);
}

void loop()
{
Wire.requestFrom(2, 1);

while(Wire.available())
{
int J1 = Wire.read();
Serial.println(J1);
}
delay(500);
}

on the Slave:

in the Setup part :
Wire.begin(2);
Wire.onRequest(requestEvent);

and after the loop part :

void requestEvent()
{
Wire.write(J1);
}

So for J1 this already work. But how can I do this with both ? J1 and J2 ?
Can I do this with a array? How is the best way?

Kind Regards
Martin

#2

But how can I do this with both ? J1 and J2 ?

You ? could ? post ? ALL ? of ? your ? code ? so ? we ? can ? see ? what ? you ? are ? talking ? about.

You could use punctuation properly, too.

#3

Hello,

for the Master device I've already posted the complete code.
For the Slave only the I2c important parts because the code is 18 pages long.

In the Slave code I have 2 Variables (J1 and J2) The values of them are between 0 and 100.
The Master should ask for them and print them in the Serial Monitor.

Currently I ony send the value of J1 to the Master and print it to Serial.
Regards

#4

Nobody here who can help me how I can I request the values of 2 variables from a slave arduino via i2c?

#5

Take a look at the code I posted in this thread

for reading registers from a DS1307.
The master should send similar messages to the Nano/slave, and the slave should respond accordingly - recognize its address, recognize the register(variable) being requested, and send the appropriate data.

#6

thanks, but I do not understand that :frowning:

in the meantime I tried the following on the slave:

void requestEvent()
{
byte buf [2] = { J1,J2 };
Wire.write (buf, 2);
}

on the Master:
#include <Wire.h>
int Platine1 = 0;

void setup()
{
Wire.begin();
Serial.begin(9600);
}
void loop()
{
Wire.requestFrom(2,2);

while(Wire.available())
{
Platine1 = Wire.read();
Serial.println(Platine1);
}
delay(500);
}

the Serial.println now gives me following output of int variable “Platine1”:
Value of J1
Value of J2
Value of J1
Value of J2 …
(J1 and J2 is swiching)

So I already receive J1 and J2 but how can I assign there values to two new variables?
thanks for any help

#7

Maybe this?

  while(Wire.available())    
   { 
    if (flag == 1){
     flag = 0;
     Platine1 = Wire.read(); 
     Serial.println(Platine1);   
     } 
   if (flag == 0){
     flag = 1;
     Platine0 = Wire.read(); 
     Serial.println(Platine0);   
     } 
}
#8

Before I read your post I’d tried that:

Wire.requestFrom(2,2);
while(Wire.available())
{
Platine1J1 = Wire.read();
Platine1J2 = Wire.read();
}

Platine 1J1 is my J1 value from Slave and Platine 1J2 the J2 value .
Is this methode ok?

I give it out to Serial Monitor with :
Serial.println(String(Platine1J1)+"<-Platine1J1__Platine1J2->"+(Platine1J2));

So I can see J1 on the left and J2 on the right side.

The next step is to read the values out of 9 Arduino nanos:

//Master für Jalousiensteuerung 11.12.13

#include <Wire.h>
int Platine1J1 = 999;
int Platine1J2 = 999;
int Platine2J1 = 999;
int Platine2J2 = 999;
int Platine3J1 = 999;
int Platine3J2 = 999;
int Platine4J1 = 999;
int Platine4J2 = 999;
int Platine5J1 = 999;
int Platine5J2 = 999;
int Platine6J1 = 999;
int Platine6J2 = 999;
int Platine7J1 = 999;
int Platine7J2 = 999;
int Platine8J1 = 999;
int Platine8J2 = 999;
int Platine9J1 = 999;
int Platine9J2 = 999;

void setup()
{
Wire.begin();
Serial.begin(9600);
}

void loop()
{
Wire.requestFrom(1,2);
while(Wire.available())
{
Platine1J1 = Wire.read();
Platine1J2 = Wire.read();
}

Wire.requestFrom(2,2);
while(Wire.available())
{
Platine2J1 = Wire.read();
Platine2J2 = Wire.read();
}

Wire.requestFrom(3,2);
while(Wire.available())
{
Platine3J1 = Wire.read();
Platine3J2 = Wire.read();
}

Wire.requestFrom(4,2);
while(Wire.available())
{
Platine4J1 = Wire.read();
Platine4J2 = Wire.read();
}

Wire.requestFrom(5,2);
while(Wire.available())
{
Platine5J1 = Wire.read();
Platine5J2 = Wire.read();
}

Wire.requestFrom(6,2);
while(Wire.available())
{
Platine6J1 = Wire.read();
Platine6J2 = Wire.read();
}

Wire.requestFrom(7,2);
while(Wire.available())
{
Platine7J1 = Wire.read();
Platine7J2 = Wire.read();
}

Wire.requestFrom(8,2);
while(Wire.available())
{
Platine8J1 = Wire.read();
Platine8J2 = Wire.read();
}

Wire.requestFrom(9,2);
while(Wire.available())
{
Platine9J1 = Wire.read();
Platine9J2 = Wire.read();
}

Serial.println(String(Platine1J1)+"<-Platine1J1__Platine1J2->"+(Platine1J2));
Serial.println(String(Platine2J1)+"<-Platine2J1__Platine2J2->"+(Platine2J2));
Serial.println(String(Platine3J1)+"<-Platine3J1__Platine3J2->"+(Platine3J2));
Serial.println(String(Platine4J1)+"<-Platine4J1__Platine4J2->"+(Platine4J2));
Serial.println(String(Platine5J1)+"<-Platine5J1__Platine5J2->"+(Platine5J2));
Serial.println(String(Platine6J1)+"<-Platine6J1__Platine6J2->"+(Platine6J2));
Serial.println(String(Platine7J1)+"<-Platine7J1__Platine7J2->"+(Platine7J2));
Serial.println(String(Platine8J1)+"<-Platine8J1__Platine8J2->"+(Platine8J2));
Serial.println(String(Platine9J1)+"<-Platine9J1__Platine9J2->"+(Platine9J2));

delay(200);
}

I hope this will work

thanks to all

#9

Why are you storing the bytes you get from Wire.read() in ints?

I suspect that that is related to your problem.

#10