GNSS Timing Breakout ZED-F9T issues with UART2

GPS/GNSS Development Boards
1

I have been getting a newly acquired ZED-F9T running. It outputs NMEA on the USB UART in U-center as well as a terminal emulator. In U-center (22.07), I have set UART2 to output NMEA at 38400 baud, * data, 1 stop, no parity. When I connect a terminal emulator using the same port settings to view output for UART2, I get a garbled message. It doesn’t look like standard wrong baud settings. It kind of looks like hex data. Attached below is a screen shot. I have adjusted baud rates and used various terminal emulators. The result is the same. Is there something that I am missing?

NMEA_out.JPG
NMEA_out.JPG1283×600 198 KB

2

Hi,

How are you connecting UART2 to your PC? Are you using a SparkFun Serial Basic board, or an FTDI cable? You will get very strange results if you try to connect it directly to a RS232 COM port. (The polarity is wrong, as well as the voltage…)

Maybe the data is binary UBX data? You say you have set UART2 to output NMEA, but have you checked that the individual NMEA messages (GGA, VTG etc.) are enabled too?

I hope this helps,

Paul

3

PaulZC, my USB-TTL adapter has a 3.3v and 5v position. It sounds like I should be running 5v for the signal level to use with ZED boards, is that true?

4

Hi Rob,

Nope. Always use 3.3V. The u-blox modules all use 3.3V IO.

Best,

Paul

5

Paul,

I have checked that the individual NMEA sentences are enabled for UART2 and have it set to output NMEA to UART2. UART2 is connected by a simple 3 conductor serial connection that I built. I soldered the connections on the board for UART2 to a female db-9 connector as follows:

UART2 Tx2 → DB-9 Pin 2

UART2 Rx2 → DB-9 Pin 3

UART2 Gnd → DB-9 Pin 5

I use this cable connection routed through an FTDI serial to usb. When connected to a terminal at the correct baud rate, the data streams through as shown on the previously attached screen shot.

When you say the polarity is reversed, are you referring to the Tx and Rx are reversed, or something else?

Is there a PDF of documentation on this board available? I have searched and haven’t found anything beyond the how-tos embedded in the web store page.

Thank you

Dallon

PaulZC:
Hi,

How are you connecting UART2 to your PC? Are you using a SparkFun Serial Basic board, or an FTDI cable? You will get very strange results if you try to connect it directly to a RS232 COM port. (The polarity is wrong, as well as the voltage…)

Maybe the data is binary UBX data? You say you have set UART2 to output NMEA, but have you checked that the individual NMEA messages (GGA, VTG etc.) are enabled too?

I hope this helps,

Paul

6

Hi Dallon,

Polarity is your issue - it is inverted. The ZED-F9T UART1 and UART2 Tx and Rx pins use 3.3V as a Logical 1, and 0V as a Logical 0. But your FTDI 9-Pin D adapter is designed to work with RS232 voltage levels, where a Logical 1 is a negative voltage (usually around -5V) and a Logical 0 is a positive voltage (usually around +5V).

Have a look at https://learn.sparkfun.com/tutorials/se … d-hardware for more detail.

All will be well if you change to a SparkFun Serial Basic board, or a FTDI cable designed for 3.3V “TTL” signals.

Best wishes,

Paul

7

I got the Basic Serial and the unit is working on both UART 1 and 2. Thanks!

8

Excellent - glad you got it working,

Paul