Quote Originally Posted by Joe S. View Post
Do you have a spare MCU pin on the reader's pics? If so you could hook the readers all to the usart with a series resistor on each, then when a reader sends data it could pull that spare pin low which signals the other readers to standby, (all spare pins hooked together). Just make sure the reader's output pins Idle in the High state.
Almost perfect and a very good idea, but I don't have any pics on the reader boards, just the RS232 (MAX 232) chip. So I can only receive the card data at the PIC.