A project log for GNSS module 2.0 - GNSS via Bluetooth

In this project I build a smaller version of my previous GNSS module. The main features are: LiPo battery, USB, active antenna, bluetooth

dechemistdechemist 11/07/2021 at 20:150 Comments

The build of the module was pretty strait forward...with some complications. Except for one all footprints matched the parts I have. The LDO for VCC_USB was the wrong footprint, a SOT-89-3 should have been a SOT-223. I fixed this by soldering cables to the pads (FYI, this exact mistake was made in the first version of the module).

I tried to solder the micro USB socket by hand and solder (wire) but could not reach all pins with the soldering iron tip. In the end I cleaned up the pads and used solder paste and a reflow station. To check my connections I connected some wires to a USB-A socket and connected a USB-A to micro USB cable to the module. Thereby I could test the continuance of GND, Vcc, D+, and D- to the PCB through the socket.

Although the connections were OK, I could not get the PC to recognize the module. Since the connections were definitively OK, I removed the USBLC6 diodes and bridged the contacts of the signal lines. Then a connection could then be established to the module via USB. Once again I have no idea why this is not working although this configuration is recommended in the u-blox NEO8 hardware integration manual. The next design will not have this protection.

For the case I used a plastic one this time with outer dimensions of 48x73x23 mm. No more chunky wood box. The USB socket is located on the opposite side than the LEDs and power switch. Most of the internal components are held in place with double sided tape. The battery is taped to the bottom of the box and the PCB is hold on top the battery in the same way. Since the antenna is not that heavy it was also hold in place with double sided tape. The LiPo charger was covered with shrink tubing and stuffed in the box.