Tx for uart1 / Rx for uart2 ?

Q&A forumCategory: QuestionsTx for uart1 / Rx for uart2 ?
amorosik asked 2 years ago

SimpleRTK2B, with pin IOREF connected to pin 5VOUT, and powered by usb cable
View / Configuration View / CFG / Revert to default configuration / SEND
View / Configuration View / PRT / Target = UART2 / Protocol Out=0+1+5 / SEND
Then Uart1 and Uart2 must output Nmea and Rtcm data
But on board header, for uart1 i see data (with oscilloscope) on pin TX1, for uart2 i see data on pin RX1  ???
The question is:  why are indications on uart1 inverted compared to uart2 ?
 
 
 

Ardusimple Staff replied 2 years ago

tx1/rx1 is intended for connection to GPS
tx2/rx2 is intended for connection to XBEE. If you switch those, you connect to UART2 GPS.

I know it’s confusing but we didn’t come up with an easier way of describing this 🙂

amorosik replied 2 years ago

How “I know it’s confusing”?
If you know it can be confusing then it is necessary to change, there are no other possibilities
And the simplest thing, is to set the directions of the GPS card from the point of view of the GPS card itself
So I think the RX2 and TX2 pins should be reversed
This if you want your customers, as happened to me, do not risk damaging the connected equipment

1 Answers
Wolfgang answered 2 years ago

UART1 TX/RX is labelled from the u-blox’s point of view, so RX is data into the GNSS.
 
UART2 TX/RX is labelled from the XBee’s point of view, in which RX means data into the XBee via RF, therefore out of the radio module.
 
It follows the logic of the respective modules. I also expected RX to mean into the Ardusimple board, so from the host’s point of view.
 

amorosik replied 2 years ago

Yes, I know what the connections are like
I discovered, unfortunately at my expense, that the RX2 signal is actually an output signal from the board
“..It follows the logic of the respective modules ..” is a logic that does not make sense, because the Xbee module in many cards will not be present
And also in the cards where the Xbee module is present, it is possible to indicate the pin assignment according to the point of view of the radio module on the Xbee socket.
There is no reason to reverse the meaning from uart1 to uart2 in the edge pin on the board

Wolfgang replied 2 years ago

Aye mate, life’s a bitch ain’t she.