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Connecting two AT89S52s with cat5 cable?

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Junior Member level 1
Jul 28, 2009
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I need to connect two AT89S52s 50 meters apart , so i need to use twisted pairs to reject noise, what pins would serve the tx+ tx- rx+ rx-, i thought i would connect both tx- and rx- to ground:

first pair: vcc,ground
second pair: tx,ground
third pair: rx,ground

so is that right, any answers would be appreciated, i can't find anything about it on the net.

I don't know much but to find out which pins doing the UART I think you can look in the datasheet.
As for the ground pair, I think it only applies to data transmission lines, Vcc no need for ground pair. Unless of course if you mean the power supply ground (GND) or 0V. But then again I think each board that holds the uc will be powered separately, right? I might be wrong, perhaps anybody else would like to share a bit of their knowledge here.

Instead using CAT5 cable, you may consider using 3+1 shieled wire as the outer most layer will be grounded to protect and eliminate any EMI/RFI. Cheers

If you need reliable transmission at reasonable speed you have to use proper twisted pair line drivers and there is no escape from that ..
The RS-485 drivers seem to be the cheapest option and as the most popular of them contain only one driver per IC you will need two IC per each end: one set up for reception and one set up for transmission ..
The first RS-485 driver (receiver) will convert differential signals RX(+) and RX(-) to single-ended Rx, the second RS-485 driver (transmitter) will convert Tx to differential signals TX(+) and (TX(-) ..

Google for LTC485, SN75176, MAX483 .. MAX485 or similar ..


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