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Why do we connect pull-up resistors to SCL and SDA lines in I2C protocol?
As discussed in the I2C Basics module, the resistors that are commonly seen on I2C circuits sitting between the SCL and SDA lines and the voltage source are called pull up resistors. A pull up resistor is used to provide a default state for a signal line or general purpose input/ouput (GPIO) pin.
Why is pull-up required in I2C?
Pullup resistors need to be connected from the I2C lines to the supply to enable communication as shown in Figure 1. The pullup resistors pull the line high when it is not driven low by the open-drain interface.
Is I2C open drain?
The Open Drain. A defining characteristic of I2C is that every device on the bus must connect to both the clock signal (abbreviated SCL) and the data signal (abbreviated SDA) via open-drain (or open-collector) output drivers.
What kind of I2C pull up resistors do I Need?
I2C Pull Up Resistor Bottom Line If you’re working with a single chip on a breadboard, just use whatever resistor value you have on hand from 4K7 to 10K for your SDA and SCL signals and you’ll be fine.
Can you use more than one pull up resistor?
If there is more capacitance then a lower resistance would be required to provide the stronger pull up in order to meet the timing requirements. As far as multiple resistances. Yes there can be more than one on the line. But the accumulated resistance must be taken into account. Many I2C devices mounted on a breakout board have pull up resistors.
Can you connect I2C devices to a breakout board?
I2C devices are sensors (BME280 here, and Chirp capacitive soil moisture, here ), not on breakout boards with preset pull up resistors. Is it possible to just connect resistors on master side and not slave side?
What’s the maximum capacitance of an I2C resistor?
The maximum of all the capacitances are limited to 400pF by I2C standard, and you’d have to have either a really long signal trace on your PCB or a lot of devices on it to get anywhere near 400pF, but as the frequency of your signal increases, the impact of that charging rate will have a dramatic affect.