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Topic: Open Drain (Read 4 times) previous topic - next topic

retrolefty



They (the electronics world) call it an Output!! but if you google Open Drain the explanation is that it can only Sink current or present a High Impedance so it cannot output anything. :) The Output definition is very confusing.

No it is not.

Sinking current IS an output. Just like sourcing current is an output.

There is no open drain or open collector configuration in an arduino. If you want one you have to use an external transistor or FET.


Well except if you enable the I2C hardware, then it's two signal pins will be open drain when in output mode.

Lefty

Nick Gammon

Can't he just use INPUT/LOW as high impedance, and switch to OUTPUT/LOW to sink current?

CrossRoads

"Can't he just use INPUT/LOW as high impedance"

That's what is needed if the internal pullup resistor is to be unconnected.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
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Firefox



They (the electronics world) call it an Output!! but if you google Open Drain the explanation is that it can only Sink current or present a High Impedance so it cannot output anything. :) The Output definition is very confusing.

No it is not.

Sinking current IS an output. Just like sourcing current is an output.

There is no open drain or open collector configuration in an arduino. If you want one you have to use an external transistor or FET.


It may not be confusing to you but it is to me.

Doesn't Sinking Current mean the current is going into the Pin?

If you I set the Arduino digital pin as an Input, and set it LOW, will it Sink Current?

If you I set the Arduino digital pin as an Input, and set it HIGH, will it present a HIGH Impedance?


Nick Gammon

Quote
If you I set the Arduino digital pin as an Input, and set it LOW, will it Sink Current?


No it won't. It will be high impedance.


Quote
If you I set the Arduino digital pin as an Input, and set it HIGH, will it present a HIGH Impedance?


It will be high impedance with an added approximately 50K pull-up resistor.

To sink current it has to be OUTPUT mode and LOW.

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