Is pull-down resistor necessary?

Is pull-down resistor necessary?

Pull-down resistors can be safely used with CMOS logic gates because the inputs are voltage-controlled. TTL logic inputs that are left un-connected inherently float high, and require a much lower valued pull-down resistor to force the input low. For that reason, pull-up resistors are preferred in TTL circuits.

Which port has built in pull-up resistor?

Port 1 P1
Port 1. P1 is a true I/O port as it doesn’t have any alternative functions as in P0, but this port can be configured as general I/O only. It has a built-in pull-up resistor and is completely compatible with TTL circuits.

What is an open drain pin?

An open-drain or open-collector output pin is driven by a single transistor, which pulls the pin to only one voltage (generally, to ground). When the output device is off, the pin is left floating (open, or hi-z).

Are there pull-up resistors on GPIO pins?

Yes, all of the B+’s GPIO pins have internal pull-up or pull-down resistors that can be controlled from your code. Pull-up is 50K min – 65K max. Pull-down is 50K min – 60K max. More info on the GPIO can be found here and here.

Can a MCU pin be a GPIO pin?

But most mcu pins are GPIO, and sometimes on startup are defined as inputs instead of outputs. As you said, sometimes you don’t want an IC pin input floating on startup, especially like a reset pin that you would normally drive with your microcontroller’s GPIO.

What’s the difference between high drive GPIO and push pull GPIO?

High-drive GPIO are push-pull pins that are capable of providing more current than typical pins. While you must check each chip’s datasheet to understand the current capacity of your pins, typical push-pull GPIO can source/sink around ±8mA, while a high-drive pin can source/sink up to ±40mA.

What does GPIO mean in a microcontroller?

Anyone who writes software for microcontrollers will have to configure and manage general purpose input/output ( GPIO) pins. On their surface, GPIO configuration seems simple: pins are input or output, and they can be high or low.