August 16th, 2009

Nokia N97 GPS Upgrade

Nokia N97 GPS Upgrade

The N97 touchscreen smartphone from Nokia was announced at the end of 2008 and was released earlier this year. With quite an impressive set of features that would satisfy even the pickiest of mobile phone users, the N97 has its share of flaws that can be very disappointing when counting on the phone to get your job done. Such a flaw is the N97’s GPS performance, which is rather poor, especially with this kind of feature-rich phone – it’s worse than N95, which is already an old model for those who follow the mobile phone industry closely. But this unfortunate defect can be remedied with some minor adjustments.

The idea of this hack is to improve the GPS performance of your N97 with ease, dismantling it with care and adding some copper wire to its antenna. Because half of the antenna wire is covered with glue, you will need to peel it first, until you get to the metal. Then, you add a copper wire (you can easily find it in all sorts of broken stuff you may have laying around) that should be placed under the GPS antenna. And that’s it, your N97 will now be more reliable since the antenna received the special high-tech upgrade presented – the addition of the copper wire!

On a side note, as the author of the original article says, I’m also baffled by the terrible performance of some of the high-end smartphones. I’m not a big fan of the GPS, but something is definitely wrong when you pay hundreds of dollars for a device that performs so bad in environments in which it was meant to function. How all of this eludes the people in charge of testing is a mystery.

Nokia N97 GPS Upgrade: [Link][via]

June 2nd, 2009

Unlucky GPS guided RC car

Unlucky GPS guided RC car

I think there isn’t any kid out there that hasn’t wanted a radio-controlled car. Well, at least us, boys. But what if you could build your own, with sonar and GSP too? Yeah, I know, pretty nifty. This project is rated ‘under development’ as it still needs some adjustments. It features an Atmega328P microcontroller, a HM55B digital compass, a PING))) ultrasonic range finder, two MC33886 H-bridge controllers and a GPS receiver chip.

While the Atmega acts as the brain of the robotic platform, the PING sensor plays the eye. Using extra pins, the latter can be mounted on a servo motor, so that the robot can look left or right. It can also smile, wave and say ‘I love you’ in fifteen languages. Kidding. Motion is acquired using two DC motors, one for forward/back, the other for turning left or right. Both of them are controlled with the H-bridge controllers which are connected to the PWM outputs of the microcontroller.

So, why is this slick RC car unlucky? Well, it seems that the PCB traces greatly influence the reception of the RF signal and the GPS signal is extremely poor. Replacing the antenna or connecting it directly to the GPS chip didn’t improve things, so contacting SkyTraq, the GPS manufacturer, was the next step in solving the dilemma. And let me tell you something, seeing that the guys who built the damn thing are willing to aid someone is always a pleasure. So, having considered their advice, the owner and constructor of the neat RC car promises a new version in the near future. Although the project does not possess sophisticated hardware or is a functioning one, it does have a certain appeal. Let’s face it, RC cars are cool. I’d play with one if I had it, I’m sure others my age would too.

Unlucky GPS guided RC car: [Link]


The idea behind this project was born when a friend asked me too take a look at he’s broken GPS unit (MyGuide 3000) to see if I can fix anything. I started checking various parts like voltage regulators, but found nothing wrong. The gps unit was still not powering up so I checked the cpu, an ARM9 from Samsung and found it broken. Of course I couldn’t do anything about that, because of the BGA package and the bootloader needed after replacing it so the gps unit became a source for parts. The most useful and interesting parts from the GPS were the LCD display and the GPS module.

The GPS module is a RoyalTek RGM-3550LP which has an integrated antenna and is powered by SiRF Star III technology. I immediately connected the gps module to my computer’s serial port(using a max232) to test if it was still working. To my surprise the gps module was working and sending NMEA compliant sentences. Then I had this idea of using the gps module as a navigation system together with a notebook computer, but notebooks don’t have a serial port so I had to use a UART to USB bridge.

RoyalTek rgm-3550lp-gps-module

The most common used UART-USB bridge is the FT232 manufactured by FTDI which is about $4 which is a fair price because you don’t need any external parts for this chip except some bypass capacitors and that saves you time and money. I never used the chip before but it was really easy to get it working. It even has this custom utility that let’s you program some features saved in the internal EEPROM like the maximum bus power and the product and manufacturer descriptor strings. Anyway these are the only two settings that I tinkered with, but the utility let’s you change some more stuff.


The next thing I had to worry was where to get the power for the GPS unit, because it needs 3.3V and the acquisition current is 50 mA. The FT232 has an internal voltage regulator which provides 3.3 V and 50 mA but I decided not to use that in order to extend it’s life so I ended up using the TPS2148 which is a 3.3V LDO from Texas Instruments. It’s specifically designed for USB peripheral power management, and it’s tiny package(MSOP-8) made it ideally for my application. The TPS2148 handles the current limitation so I didn’t had to worry about that either.


After figuring out the parts I was going to use and the schematic, I had to chose an enclosure for this project. The main target was to get it as small as possible but the limit was the gps module size, I couldn’t of got it smaller then the module :). So I went and searched for a plastic enclosure, and I found one just perfect for what I needed, the PP85D from Supertronic. The gps module fits just nicely between the screw channels.

Then after I got the enclosure, I made the pcb using the photo etching technique.. I assembled and tested it, and to my surprise everything worked just fine from the first try. I’m usually not that lucky when I make stuff using new IC’s that I haven’t used before. Sometimes I don’t pay enough attention to the datasheet and I get some small stuff left behind and that messes my entire circuit. Anyway, happy as I was that everything worked from the first try, I put everything inside the enclosure and snapped some pictures of it. As a final note, this was a great project which I enjoyed making, and I really recommend you do something like this if you have a gps unit laying around.

more pictures:

parts-for-the-usb-gps-project gps-module-and-pcb ft232rl-board

board-inside-the-enclosure pcb-with-gps-module-inside-the-enclosure new-hardware-found

parts list:

  • RGM-3550LP gps module x1
  • FT232RL x1
  • TPS2148 x1
  • capacitor 10uF x3
  • capacitor 100nF x3
  • led x1

schematics and board files were designed in Eagle and can be downloaded here.

May 12th, 2008

AVR Butterfly GPS System

AVR Butterfly GPS System

The handy Butterfly GPS is a cost-effective system that presents location, date, and time data on its LCD. The system features an ATmega169 and a highly sensitive GPS receiver engine board based on the SiRF chipset. Its amazing what you can do with such a low cost development board.

AVR Butterfly GPS System: [Download Project][View Project PDF]

April 24th, 2008

Open GPS Tracker System

 Open GPS Tracker System

The Open GPS Tracker is a small device which plugs into a $20 prepaid mobile phone to make a GPS tracker. The Tracker responds to text message commands, detects motion, and sends you its exact position, ready for Google Maps or your mapping software. The Tracker firmware is open source and user-customizable. This looks like a great project if you’re into GPS projects.

Open GPS Tracker System: [Link]

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