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RTS & CTS not swapped


#1

Can anyone tell me why RTS and CTS lines are not swapped in XBee module (http://www.ghielectronics.com/downloads/schematic/XBee_Module_SCH.pdf )? Is it a mistake?

Are pull-up/down resistors required for RTS and CTS lines? I have seen for example 1k pull-down resistor used for RTS line.


#2

Why would they be swapped? No need for resistors.


#3

I was under impression that all UART lines are swapped:


#4

Correct but they do not need to be swapped on the schematic you are looking at as they are swapped on the other end…The other part of the design…The main board


#5

Hmm… So you are saying that RX & TX lines are not swapped on the mainboard, but CTS & RTS lines are? That would be very strange and confusing.

K socket pin-out:
1: +3.3V
2: +5V
3: GPIO!
4: TX (G)
5: RX (G)
6: RTS
7: CTS
8: [UN]
9: [UN]
10:GND

From XBee schematics I see that RX is connected to 4th pin and TX is connected to 5th pin. So these two lines are swapped. But CTS & RTS are not swapped.


#6

So, can anyone explain? It’s still not clear for me.


#7

You maybe right! I am confused now… will look into it


#8

On the XBEE modules RTS is an INPUT and CTS is an OUTPUT so the wiring would be correct.

The use of RTS and CTS in the XBEE modules is opposite convention to what some would consider normal use with RS232. The convention is actually correct as the XBEE modules are DCE (Data Communication Equipment) and the processor modules would be DTE (Data Terminal Equipment)

XBEE uses DIN and DOUT for the transmit and receive so mixes different terms.

The only time you have cross over is when you connect DTE to DTE or DCE to DCE.