I've bought a Microstax GPS unit which I'm using directly on my RPi 3 (no Microstax headerboard). I've got the unit connected correctly though I'm strangely seeing a few seconds of correctly formatted NMEA GPS data then the majority of which is just garble which will return a few seconds of NMEA data, then garble again.

I've replaced cables and the like - not sure what it could be other than the unit not getting enough power from the Pi 3.3v rail (it's only supposed to draw 20mw). Any ideas? Stumped.

  • What is the serial configuration you are using. Maybe the garbled data is the device sleeping?
    – Piotr Kula
    Aug 8, 2016 at 11:32
  • I'm monitoring using minicom @ 9600baud. I dont think it's the device sleeping (it shouldn't sleep) Aug 10, 2016 at 6:39

1 Answer 1


The Microstack GPS looks as though it uses the VK16E module that I'm using with my RPi2.

I found that I needed to up the power supply to get a steady NMEA stream. With a low power transformer (750ma) the Pi would boot, but the GPS wouldn't Sync with satellites. I could see pulses of correctly formatted NMEA but it didn't contain anything useful.

When I changed to a 1A supply the chip acquired the satellites in a few seconds and NMEA was good.

[I assume that you've disabled any other ttys on the serial line that might interfere.]

  • I have. I was suspecting it may be power draw when trying to get a fix. The 3.3v rail on the Pi3 is weak compared to the 5V rail and the VK16E appears to have a voltage reg on it. Off to the parts supplier... Aug 10, 2016 at 6:38

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