I2C isn't working properly with my sensor

Other Hardware Sensors
1

Hi there

I've been trying to get my ov7670 camera to work with arduino.
(For those of you who know the sensor) I've been applying a clock signal to XCLK, powering 3v3 and RST with the arduino 3v3, GND and PWDN with the arduino GND and I've attached the arduino and ov7670 i2c pins to a level shifter (the ov7670 uses a 3v3 i2c instead of a 5v).

I've used an i2c scanner and I find if I scan a few times the device might appear once or twice.
I wrote some code to read registers from the device, and it occasionally works:

      Wire.beginTransmission(0x21);
      Wire.write(0x01);
      endput = Wire.endTransmission();
      Serial.print(endput); Serial.print("_");
    delay(25);          
     Wire.requestFrom(0x21,1);
     output=Wire.read();
     Serial.print(output); Serial.print("_");
    delay(200);

However, when I try and write to the registers it fails.

      Wire.beginTransmission(0x21);
      Wire.write(0x01);
      Wire.write(0x11);
      endput = Wire.endTransmission();
      Serial.print(endput); Serial.print("_");
    delay(25);          
     Wire.requestFrom(0x21,1);
     output=Wire.read();
     Serial.print(output); Serial.print("_");
    delay(200);

I've tried 10k pull up resistors (with and without the wire internal pullups disabled) and still failed to write to registers, although I can read the registers occasionally.

Does anyone know what might be going on with my sensor? :slight_smile:

2

I2C should not require a level shifter.
The arduino should only pull the line low, never pull it high. So you can hook your pullup resistors to 3.3v

Without running a calculation, I think a pull up of about 5k may be a good starting point. [ actually, since we are pulling up to only 3.3v, maybe a 4k would be better ]