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Questions tagged [open-drain]

Questions about Open-Drain devices and protocols. Open-Drain connections have two states, Open/Floating, or Drain to ground. Typically require Pullup resistors.

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9
votes
4answers
14k views

Open-drain microcontoller ports

I want to understand the concept of open-drain ports like port P0 of the 8051 microcontroller. Why do we need to connect pull up resistors to the port P0? I have basic knowledge of MOSFETs and other ...
3
votes
4answers
186 views

multiple Open Drain UART over long distance [duplicate]

I have 9 microcontrollers ATMEGA3208 and I have connected the RX and TX lines of 8 of them in parallel. My configuration is in master-slave. The master microcontroller send data to one of the 8 RX ...
3
votes
1answer
6k views

Driving a LED with an open drain digital output

I need to drive an LED from an STM32F217ZG. So I was thinking about a classic circuit with a BJT. But then I saw that GPIO outputs of the microcontroller are configurable as open drain. Would this ...
1
vote
2answers
1k views

Why does the I2C interface use the open-collector/open-drain?

The open-collector adds inconveniences like requiring an external pull-up resistor and slows down the throughput. Why did the I2C designers choose to use open-collector/open-drain?
3
votes
1answer
2k views

Confused between push-pull and open-drain

I am planning to use i2c based port expander (earlier I was using atmega328P's GPIO) for inputs and outputs. On a digikey search, I found MCP23008, MCP23009 and MCP23017 as possible replacements. Out ...
1
vote
2answers
323 views

Can Transmission gates be used to implement 3 State Logic?

In my application i need to use a common line shared between two peripherals, i have to indicate to the devices whenever the bus is free or not, hence i can't have push-pull output where the output is ...