USB GPS dongle on UART and Raspberry Pi

1

I bought this great USB dongle with the ublox Neo-6t chip on it. I want to fit it in a small raspberrypi housing. So I try to connect it not via USB but via the labelled holes on the board. I connected GND to GND, 5V to 5V, TX to RX and RX to TX. I left “INT” empty.

What I expect is that when I type sudo cat /dev/ttyAMA0 I get the GPS data stream directly without USB. When I connect the module via USB I expect getting the same via sudo cat /dev/ttyACM0.

But what happens is strange: When I connect the module without USB I get nothing (but the leds on the module indicate a fix). When I connect the module both with USB and UART I get a reading on ttyAMA0 and ACM0. When I connect USB only I get the reading on ttyACM0 only.

How can I get rid of the USB cable?

2

The connection seems correct. By default Raspberry Pi has serial console enabled on /dev/ttyAMA0. Did you disable it? It can be done with raspi-config - advanced serial console - disable.

Also, it is necessary to work with a proper baud rate. Default UART baudrate for U-blox NEO-6T is 9600.

The easy way to check if it works (if serial console is disabled) is to use screen like this:

sudo apt-get install screen
sudo screen /dev/ttyAMA0 9600

You should see NMEA or UBX messages coming in. To exit screen press CTRL+A then K then Y.

If it still doesn’t work try switching RX and TX lines.

3

Thanks. I had serial console disabled with raspi-config. I get the NMEA messages on UART when the USB cable is plugged in but not otherwise.

If anything would be wrong with baud rate I would see unreadable content. But if I disconnect the USB cable I get nothing on ttyAMA0. If TX and RX would be wrong I suppose I would not get anything even if the USB cable would be plugged in.

4

That’s very strange. Could you please post pictures of how everything is connected and screenshots of what’s going on?