| ??? 03/16/07 21:58 Modified: 03/16/07 22:24 Read: times |
#135149 - agree Responding to: ???'s previous message |
Erik Malund said:
I am planning to put the master & slave boards in one enclosure , so they will be usually not more than a foot apart at the farthest end.
no need to use RS-485, you can connect the pins directly. So the question is academical. Cross-connection of RX-TX may be apropriate. The only question I have think about always is: if MCU uses pin for a special function (not as a port output one but as special function pin like UART, SPI etc) -- what is the pin`s current for "off" state? By other words, if some slaves have TX pins connected together - do they keep them as weak pull-upped or tie them as strong "1"? In my opinion, special function of some vendors may utilize strong pull-up to keep noise low as possible. So such connection (in theory) may provide short circuit between active slave transmitted "0" and others slaves which try to keep strong "1" due "off" state. I am sorry - I never tested it for many different vendors so have no answer for all of them. Regards, Oleg |
