Globalsat BU353 S4 GPS Receiver showing garbled messages

I’m working on a project using a Globalsat BU353S4 GPS receiver but I’ve had garbled messages being returned when reading the data through the serial connection. What I’ve realised is that somehow the device has switched from NMEA to SiRF. I suspect this happens if you’ve been fiddling with the settings using python 🙂

You need swap your device from SiRF mode back to NMEA using the tool below.

Globalsat BU353S4

If you tested it with GPSInfo and you see garbage characters coming out, then, the device has possibly switched to SiRF mode. To switch it back to NMEA mode, please refer to the instructions below:

1. Download and install this software:
2. Run the Sirf Demo software.
3. Connect your device, choose the correct COM port, and select the 4800 baud rate.
4. Go to Action > Open Data Source.
5. Next, go to Action > Synchronize Protocol & baud rate.
6. Then, go to Action > Switch to NMEA Protocol.
7. In the pop-up window, select the 4800 baud rate under the Baud Rate and click Send.
8. Close the Sirf Demo software.
Note: Be sure and not to click on anything else in this software, as you can render your device unusable.

Now, try your GPS Receiver with the GPSInfo Utility ( to see if the problem persists.

I came across the solution here –