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Why I2C need pull up resistors?
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.
Do I2C lines need pull-ups?
Unlike UART or SPI connections, the I2C bus drivers are “open drain”, meaning that they can pull the corresponding signal line low, but cannot drive it high. Each signal line has a pull-up resistor on it, to restore the signal to high when no device is asserting it low.
How many pull up resistors for I2C?
I2C Current Specifications and Bitrates The I2C specification allows a maximum of 3 mA pull-up current on each I2C line. The Aardvark adapter has two internal pull-up resistors on each line: 2.2k ohm and 100k ohm resistors in parallel. The 2.2k ohm resistor can be turned on and off.
What does a pull up resistor do?
In electronic logic circuits, a pull-up resistor or pull-down resistor is a resistor used to ensure a known state for a signal. It is typically used in combination with components such as switches and transistors , which physically interrupt the connection of subsequent components to ground or to VCC.
What is a weak pull up resistor?
A low resistor value is called a strong pull-up (more current flows), a high resistor value is called a weak pull-up (less current flows). The value of the pull-up resistor needs to be chosen to satisfy two conditions: When the button is pressed, the input pin is pulled low.
What is an internal pull up resistor?
Pull-up resistors may be discrete devices mounted on the same circuit board as the logic devices . Many microcontrollers intended for embedded control applications have internal, programmable pull-up resistors for logic inputs so that minimal external components are needed. Sep 16 2019