Hi, I am trying to build a very simple MPPT circuit by using controller as an Arduino Nano. It will be for middle school students so its very low power and doesnt have to be very efficient. Actually it must be very clear, simple and understandable for them.
My question is: I normally use ESP32 without a module and if I use a sensor with I2C; for SDA SCL I place pull-up resistors to 3v3 with 5.1 kOhm. I believe since I am going to use a Nano Module it will have this pull up internally so that I don't need to do put extra resistor right ? Just a connection between SDA SCL should be enough
As in the schematics below (this has resistors which I am planning to remove)
The internal pullup resistors built into the input pin circuitry of AVR processors, like on the Arduino Uno R3 or Classic Nano, have values in the range 30K to 50K, if enabled. They may not be enough to support communications on the I2C bus.
You need only one set of pullup resistors, one each for SDA and SCL. Most people choose them to be the range of 2.2K to 4.7K. The higher the value, the less reliable communications in a noisy environment, or long leads or significant capacitive coupling to other conductors.
Why?
I2C lines are "normally HIGH", so the pull up resistors have no voltage across and don't consume any power (if that's your concern).
The lines are only pulled LOW during the very short data exchange so no noticable effect on current draw.
Two sets of 5k1 and internal 33k is 2.37k combined, which is nothing to worry about.
Leo..
