No fix on u-blox neo 6m

There could be an issue with BP’s oscillator harmonics. The ~21st harmonic of the 72MHz may jam the GPS receiver.
As an experiment, try to change the BP’s clock, what happens.

Hi. In reverse order. I’ll change to 48 Mhz, to see if that will have some effect (I’m using a ST-LINK to upload and I’m using Serial3 for serial).

I’ll look into the DC to DC isolators, hopefully those could help, if I can get my hands on those soon enough.

Btw, here are the pictures of the setup. Essentially I have the same on another breadboard but with Pro Mini, and the same setup works.
https://www.dropbox.com/sh/usmsbtvekcj1 … W9APa?dl=0

Sidenote, I’m also having problems with my LoRa module and the LMIC, but that is a problem for another day. I’m using the modified version of LMIC by Tomtor, but I’ll ping him directly for ideas on the email from github, although I suppose the issues might be related to the one I have with the GPS.

OK, I tried with 48 Mhz. That didn’t help but I still think it’s not a RF problem, because as I mentioned, as long as the GPS is connected to either the GND or any of the RX/TX pins on the Blue Pill, the GPS doesn’t work. This is when the Blue PIll is not even powered. Again I repeat, the MCU is not powered.

As I mentioned, if the RX/TX pins are connected from the GPS to the Blue Pill, this causes the power pin of the Blue Pill to blink too. Again the Blue Pill is not connected to either GND or Vcc.

I’m using 3.3 external LDO to power he devices btw.

I wonder, could the GPS breakout board be the problem, as I think it is 3.3/5V tolerant, could the level shifting cause problems?

Is the GPS 5V device?? Are the GPS’s TX/RX 5V logic?
If yes then you are powering the BP via the internal BPs clamp diodes from the GPS’s TX/RX pins as they are 5V idle.
Put 1k (or 2k2 or 3k3 or 4k7) resistors in series with Tx and Rx:
BP TX ——[1k]—— GPS RX
BP RX ——[1k]—— GPS TX

This is a 5V tolerant device. It is one of the so called Neo-6M GPS from the Chinese manuf. Actually it has the exact same LDO as the one on the Blue Pill. I tried with 2k2 in series with TX/RX. Same situation. If I connect this device with the exact same setup on another breadboard with ProMini (8V/3.3) everything works. The GPS works if connected to USB-to-serial converter. Once I connect it to the Blue Pill (GND/RX/TX) the GPS goes crazy. Seems the only pin that does not affect it is Vcc. And this is when connecting to a Blue Pill that is not even powered on.

The only thing I haven’t tested is to connect the GPS directly to the Blue Pill without the breadboard. *The breadboard is OK, as the 10DOF is working fine on the I2C.

Completely stunned by this situation. I know there is communication between the GPS and the Blue Pill, but the data is corrupted for some reason. The serials on the blue pill are fine, tested them with serial to USB and the GPS is ok, again USB to serial. Also GPS to Arduino is fine. I’m getting frustrated as I’m trying to build a POC, but I would like to use HW Serials and the AVRs don’t have enough (except the Mega, which I don’t have around currently)

If I connect this device with the exact same setup on another breadboard
BTW, there are breadboards which do not have continual GND and VCC rails, you must use jumpers. Just an idea when all is the same but only the breadboards change..

+1

I think you should try without the breadboard, its a nest of various lengths of hundreds of wires, all capacitively coupled together.

Use a single ground, put RF chokes in both ground and supply to the BP, keep wires short. If necessary, shield the BP inside a aluminium foil box.

Hi Roger and all,

Just coming back to report back. I basically discarded the breadboard, connected the GPS directly with jumper wires to the Blue Pill and everything works pretty nice. Then connected the 10 DOF IMU to the I2C, both working fine.

On that note, I can confirm that TinyGPS++ works nice on the Blue Pill, also NeoGPS works pretty nice too in NMEA mode.

Now let’s see if I’ll be able to make the InAir9B work. I connected it to another Blue Pill, and I just started debugging.

Thank you all for the support. Sidenote I always hated breadboards, but when prototyping with a lot of sensors it’s usually handy.

Thanks for letting us know the outcome.

Can you change the thread title, to indicate you now have a fix.

Hi Roger, sorry for not getting back earlier, got a bit of a flu or something. This actually is not my thread, I shamelessly hijacked it, because it was exactly the same situation I was facing. Sidenote, with a bit of help from Tomtor LoRaWAN is working flawlessly with Arduino-LMIC lib. I don’t know what is the proper way of reporting working libs, but if someone does a search – LMIC works, you just need tomtor’s LMIC github repo.

People sometimes post to the libraries section if they have ported a library, or if they find a particular library works with no changes.

I should probably formalise this.

I should probably do something similar for hardware, e.g. I tried one of those H Bridge motor controllers the other day, and it seemed to work fine wirh 3.3v PWM

[RogerClark – Wed Jun 21, 2017 10:36 pm] –
People sometimes post to the libraries section if they have ported a library, or if they find a particular library works with no changes.

I should probably formalise this.

I should probably do something similar for hardware, e.g. I tried one of those H Bridge motor controllers the other day, and it seemed to work fine wirh 3.3v PWM

Sounds like a good thing to put in the Wiki, perhaps a section for working hardware and a section for working libraries.

Ilf, thank you for reviving this post. I actually could not resolve the issue. Even changed the LDO for two maple mini clones with no results, but never tried removing the breadboard from the equation. I’ll give it a try today so we can have a larger sample of results.

[jucordero – Fri Jul 14, 2017 12:40 pm] –
Ilf, thank you for reviving this post. I actually could not resolve the issue. Even changed the LDO for two maple mini clones with no results, but never tried removing the breadboard from the equation. I’ll give it a try today so we can have a larger sample of results.

… There is not an issue with Neo 6 and the Maple Mini clone – I have used both many times with Adafruit’s GPS library and even my own non-library parsing function. I do however use the 9600 BAUD default serial speed of the ublox.

Example project

When the Neo6’s arrive from China, they will take a very long time to get the first fix; My worst case was over 10 hours.

Ray

Ray,

Can you an approximate location to the GPS to help it with its initial fix?

I think some GPS units support this.

Also puttin the unit outside so it gets a clear view of as many satellites as possible normally speeds up acquisition time.