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LAUNCHXL-CC1310: Sub-1 GHz forum

Part Number: LAUNCHXL-CC1310
Other Parts Discussed in Thread: CC1310

Hello,

I am trying to use onboard UART (on CC1310 TI launch pad reference board) to talk to a device that takes in serial port (UART). Just needs RXD, TXD and GND. I have read all available documentation on this forum but still facing issues. Here is a description. I am basically using uartecho.c example (slightly modified). I see this strange behavior.

(1) When I load and run the simple echo program, everything works fine on CCS built-in terminal, if RXD and TXD are connected thru XDS onboard debug chip. All good.

(2) When I remove RXD and TXD jumpers from connector (XDS) and connect them directly to a RS232-USB connector and a terminal program on Windows (like tera-term) I start seeing issues. Basically characters are garbled on terminal screen. It seems that characters appear fine on terminal when they are sent thru XDS chip but have issues when RXD, TXD pins are directly connected to terminal com port 

(3) I did try a bi-directional level converter in between board RXD, TXD and RS232 to USB converter (just to make sure TTL levels will be driven out) - Still same result garbled characters.

(4) Terminal program setup is fine, since I can use it to directly talk to peripheral (baud rate 19200) and I can send and receive data to peripheral.

(5) The problem is only when I use board pins to drive the data out (and receive) via board pins (I have buzzed them to make sure connections from XDS connector to header pins are correct).

(6) I also fully isolated XDS chip (as suggested in some E2E discussions), still have garbled characters o/p

All in all, it seems when CC1310 TXD and RXD go thru XDS chip - everything is fine but if I bypass XDX chip things start going wrong (as if XDS chip processed these signals).

Tried both blocking and non-blocking version but the problem is same.  Have also tried a few boards just to make sure. 

CCS version  Version: 12.1.0.00007 

Any suggestions?

Sham Datta.