tom dunigan

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8 years, 6 months ago.

sparkfun em406 GPS breakout

I have an older sparkfun EM406 GPS breakout that I've used with lots of MCU's. I recently successfully exercised it on mded LPC1768 and K64F, but when I hooked it up (5v/grnd) to my F446RE, the red LED came on, but never started flashing (indicating sync'd with GPS satellites). F446RE is powered via USB, and i'm using the "arduino headers" for the 5v and ground. If I hook GPS back up to the K64F, LED comes on and begins flashing. If i hook it back to the F446RE, still no flashing LED .... I checked voltage (bout 5.02v) and even monitored current 28-29ma on F446RE, though current via K64F is 25-32 ma. I even tried providing 5v from K64F with common ground to GPS and F446RE, but GPS module stops flashing soon as I plugin USB cable for F446RE??

stumped.

Question relating to:

Last updated: 15 Mar 2022
Affordable and flexible platform to ease prototyping using a STM32F446RET6 microcontroller.

1 Answer

Wim Huiskamp
8 years, 6 months ago.

Assuming that powersupply is good, maybe the F446 generates too much RF noise and blocks reception of the weak GPS signal. Try separate powersupply for Nucleo and GPS and change distance between the two to see if GPS blinking LED comes back on. Try shielding the F446 and/or HF filtering the 5V.

I think you're right , too much RF noise. I tried an optoisolator on the GPS PPS line (and separate power/grnd for the optoisolator), but no luck. Even with no wires from the nucleo, when it's powered on and within 6" of GPS, then GPS LED stops flashing. I also tried another GPS (ultimate GPS)... nope.

posted by tom dunigan 02 Nov 2015

Ok, so a piece of grounded metal or a pcb with a full copper layer may be enough as a shield to reduce the RF noise. Perhaps a small pcb on top the F446 will do the trick. Another solution may be to run the F446 at a slightly different clockspeed.

posted by Wim Huiskamp 03 Nov 2015