Gpi ss4 no flycut3/16/2023 You enable these internal pull-ups/pull-downs at the time of setting up the port for input or output, by adding an extra, optional, argument to the tup() function call. How do you do that? RPi.GPIO to the rescue. This means we can eliminate our pull-down resistors for the button – as long as we enable the internal ones. This was to demonstrate the idea.īut, in fact, the Raspberry Pi has built-in pull-up and pull-down resistors which can be enabled in software. In our button circuit, we used resistors to pull down the voltage. What’s all this about internal ones then? You can easily get it under control by using pull-up or pull-down resistors, so that’s what we do. Or Granny might be sent back upstairs when she wants to be downstairs. If that port is susceptible to random changes of state, the propellor might spin when it shouldn’t and hurt someone. So imagine the situation where you have a motor with a propellor on it, or one which controls Granny’s stairlift, which is controlled by a GPIO input port. Any wires attached to the GPIO ports act as antennae for this radiation (it’s mostly radio waves). It is susceptible to random electromagnetic radiation or static from you, from any devices near or far and from the environment. If you have no pull-up or pull-down resistors attached to an input port, its status is not clearly defined. I mentioned in day 5 that we’d cover this in more detail, so that’s what we’re doing now. This gives it a “default” state of 0V (0, LOW, False). In the button circuit, we’re using resistors to “pull-down” the port.
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