Multiplexing UART

VEX V5 Technical Support UNOFFICIAL Tech Support
#1

Hi everyone,

Is is possible to multiplex the UART port of the VEX Cortex? Right now I have one that’s being used by the LCD and another by an RFID reader but I would like to add another RFID reader.

Thanks in advance.

#2

Depends on if the RFID reader can tri-state it’s serial data out. You already have the /Enable input that you could use to select between one RFID reader or the other.

#3

And if you can’t get the RFID reader to go Hi-Z, you can always add some simple external logic to multiplex if needed. All the signals are at friendly TTL levels, so there are plenty of chips that could do the job.

A 74LS138 would let you drive 8 different TX lines, and a 74LS151 would let you select between 8 RX lines.

Cheers,

  • Dean
#4