if Rx is connected to the Tx, why do half duplex hubs need crossover cables between each other? it looks like half duplex only uses Tx for transmission? would it not then make sence to only use straight through cables regardless?
SPI with a single master and single slave device is sort of full duplex, but when you have multiple SPI slaves you have the same issue with the MISO line. Each SPI device has to be tristated from the SPI until it is addressed with it's own Chip Select. So it's really not any different in design practice from I2C or any other bus where the slave transmit (to master) line has to be tristated.
I have a friend who says this is not correct for I2C which is an open drain system. We googled what is the difference between Tristate and open drain and it says something about current that the open drain does not allow any current. My friend says that is why the tristate does not work for I2C. Please help me understand if my friend is correct or not.
