TerryC65 wrote: ↑
Mon Sep 17, 2018 4:00 pm
I'm sure I've read somewhere that GPIO pins are open collector. If so, we should be OK but we'd like to be sure.
I don't know where you think you've read that, but they're almost certainly not open collector.
There is no requirement for pull-ups to be enabled when in output mode which there would be if they were open collector. It would limit the low to high transition time with any form of capacitive load, as it would be charging via those pullups (around 50k if the same as the input ones).
I believe they are driven both high and low.
The only exception is when specific GPIOs are in their I2C mode, in which case they are open drain, and pull ups are required.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
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