Arduino Zero I2C strange behaviour

Other Hardware General Electronics
1

Hello guys,

I am having monochrome i2c ole 128x32 display and when using arduino uno to search for i2c device I can find it,but when I switch to arduino zero i2c scanner it seems that it can't find it.

Is there anny difference between the two boards ?

2

Hi,

I noticed that the zero runs @3v3, not 5v as the uno.

3

I'm not sure if the Zero supports I2C on the A4 and A5 pins. It refers to the SDA and SCL pins. Those are on the other side of the Zero.

4

I am not using analog4,5 as sda,scl

5

I notice a similar problem using the i2c_scanner with the Arduino Zero. It doesn't work with this board(?).

I have the SDA and SCL pins on the Ardunio Zero connected to two slaves (OV7670 and MPU-6050) as shown below, with a 4.7kOhm pull up to 3.3V on each line.

I assume the following:
OV7670 is at 0x42 and 0x43
MPU6050 is at 0x68
but I want to verify with i2c_scanner.

I ran the i2c_scanner code and it returns "Unknow error at address" for all addresses. I tried disconnecting each of the slaves to run the i2c_scanner again with just one slave on the bus, but same problem for each slave device.

I can communicate with the MPU6050 via I2C knowing the address, but the OV7670 is giving me trouble...that's for another thread.

I tried playing around with the i2c_scanner code (see below) to see if there is another way of finding valid addresses. I don't know if this would work on other boards, as I only have an Arduino Zero, but I notice it hangs inside of Wire.requestFrom(address, numBytes) when the address isn't valid. I welcome input. Especially on how to step out of this function when the program is hung inside waiting.

One more note, I'm new to Arduino and haven't found a better way to debug than using the serial monitor. :slightly_smiling_face:

void setup()
{
  Wire.begin(); //join i2c bus
  Serial.begin(9600);
}

void loop()
{ 
  for(address = 104; address < 127; address++ )//Start at known valid address
  {
    bool flag = 1;
    
    Serial.print("checking address ");
    Serial.println(address);
    
    Wire.requestFrom(address,10);//guessing 10 bytes is enough
    Serial.println("debug1");
    
    while(Wire.available()) 
    {
      Serial.println("debug2");
      int b = Wire.read();
      Serial.println(b, HEX);
      flag = 0;
    }
    
    if(flag)//wire not available
    {
     Serial.println("nothing at this address");
    }
    Serial.println("debug3"); 
    error = Wire.endTransmission();
  }
}

Serial monitor output:
I2C Scanner
Scanning...
Unknow error at address 0x68
Unknow error at address 0x69
.
.
.
Unknow error at address 0x7D
Unknow error at address 0x7E
No I2C devices found
checking address 104
debug1
debug2
A
debug2
28
debug2
6F
debug2
6F
debug2
94
debug2
66
debug2
0
debug2
0
debug2
0
debug2
0
debug3
checking address 105

It is hung waiting for a slave at address 105.

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