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Ublox NEO-M9N GPS breakout board

Custom PCB created to test the u-blox NEO M9N GPS module

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This project is a custom PCB created to test the new u-blox NEO-M9N GPS. I want to study the circuit necessary to drive the NEO-M9N module and familiarize with the PCB design. The main goal is integrate the u-blox module in my GPS logger or any other personal project without having to buy and add an external board.

This project is a custom PCB created to test the new u-blox NEO-M9N GPS module. It is designed from scratch by studying the u-blox data sheet and integration manual.

The board has a built-in micro USB interface which can be used for both power supply and high speed data transfer. Connected to a computer can communicate with u-center: the u-blox GPS evaluation software for Windows. 

In order to power the module via USB, the jumper located on the side of the board must be closed. The board can also be powered providing 3.3V (jumper must be open) and controlled by using the UART (Tx, Rx) or I2C (SDA, SCL) breakout pins. It works great with the NeoGPS library for arduino.

There are two status LEDs: the green one indicates the power status, the blue one indicates the PPS. It starts to blink once the GPS has a valid fix.

The board contains an SMA antenna connector and a battery holder for hot module start to achieve a minimal time to first fix after a power down.

Please note that the design of the PCB is not optimal, in particular the RF trace coming from the antenna - as stated in the u-blox integration manual (page 85) - "must be shielded by vias to ground along the entire length of the trace". Also, the RF trace impedence was not calculated correctly and some other design mistakes. I will improve the design in a future version, but despite these mistakes the board works fine, please watch the cold start test for a demonstration.

I have tested the board with the following two antennas:

High performance active antenna

High Performance Active Quad Helix Antenna

Please check out the results on my GitHub page of the first quick comparison of two tracks recorded with this board and the NEO-M8N evaluation board that I purchased.

Gerber_PCB_v1.zip

Gerber files of version 1.0.

x-zip-compressed - 70.71 kB - 11/20/2021 at 23:40

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BOM_Ublox M9N custom board_2021-03-01_00-21-49.csv

BOM Bill Of Materials file of version 1.0.

Comma-Separated Values - 4.72 kB - 11/20/2021 at 23:38

Download

Adobe Portable Document Format - 68.57 kB - 11/20/2021 at 23:36

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  • Cold start timing test

    nottheworstdev11/29/2021 at 00:26 0 comments

    I made a cold start test connecting the GPS module to the computer using the onboard USB connector. The u-center software immediately recognizes the module and starts to display the GPS data. 

    In this test the antenna doesn't have a full view of the sky because it is positioned on the window sill and the wall of the house is blocking the South portion of the sky. This is clearly visible from the Satellite Position View in the u-center map, only the upper half of the map shows the visible satellites. Despite the non-optimal position, 30 seconds for the cold start is pretty good. 

    The design of the board can be improved a lot, I made some mistakes calculating the RF trace impedence and some other mistakes caused by my little experience in PCB design.  U-blox did a great job with this module that seems to be very tolerant to noob mistakes.

    The test was made using this active antenna.

  • Second reflow attempt

    nottheworstdev11/28/2021 at 00:32 0 comments

    The second reflow attempt is a success. One of the key points to take into consideration when applying the solder paste is to make sure that the stencil adheres perfectly to the surface of the pcb. Apply the right amount of paste to cover all the pads by spreading it with a sufficient pressure by holding the squeegee with an angle of about 60 degrees to the stencil. Too much pressure can cause "bleeding" of the solder paste between the stencil and the PCB.

    Some of the pads, especially the ones of the GPS module, are shorted or "bridged" by the solder paste but it is fine. Once the hot plate starts to heat the board reaching the reflow temperature, the paste will be "attracted" by the pads and the solder mask ensures the separations.

  • First soldering attempt

    nottheworstdev11/21/2021 at 03:20 0 comments

    The GPS module is a 24 pin LCC (Leadless Chip Carrier) package which is almost impossible to solder using a conventional iron. I wanted to make experience with reflow soldering so I bought the Kester Lead Free No-Clean Solder Paste and this heating hot plate.

    Using the stencil I made all the possible mistakes applying the solder paste, the result was this ugly looking thing:

    Even though I was sceptical, all the passive components are soldered pretty well but the pins of the micro USB connector and the UL26 ESD protection chip are all shorted. I tried to fix them using the solder but eventually I decided to remove the GPS module by heating the board and make a second attempt paying attention to apply the solder paste correctly.

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