DIY Cellphone, Part 2

The last couple of days I have been trying to put my cellphone together. Using soldering paste with lead requires good ventilation. The fumes are poisonous and you shouldn’t breathe them. That’s why I had a big fan by my side. Your friends are; soldering paste, flux for the hard ones, a soldering iron, a tweezer and patience.

I discovered that I didn’t receive the correct LiPo charger and I haven’t been able to power the phone in order to program and use it. I have contacted the supplier (Electrokit) and I am sure the they will find and ship the correct one. Still I have to wait over the weekend before I can use my phone, which is not fun =(

Here are some pictures from the soldering procedure:

DIY Cellphone, Part 1

I believe in a society like today we need to have better control over our communications. Today’s smartphones have been accused of being devices of mass surveillance. Therefore I have decided to build my own cellphone. I found this guide on the internetz, which describes an open source cellphone platform based on a GSM module and an AVR microcontroller. I selected it as a starting point of my cellphone. It will most certainly receive software updates from me (I want snake!), and probably even hardware updates in the future. Yes I know, GSM is not secure at all, and it is vulnerable to man-in-the-middle attacks, but I still prefer the man-in-the-middle over nsa-over-the-internetz.

Enough jabber for now, let’s get to the fun part! So far I have received all the needed components from the Bill of Materials (BOM) for the LCD version of the phone, besides the PAS414HR-VA5R SuperCap, which has been discontinued. Since the proposed replacement part isn’t good enough, I managed to find some left over PAS414HR-VG1 at Farnell and ordered a few of those instead. It will take some scratching and soldering to fit it on the PCB but it’s values are the correct ones. Since I am living in Sweden, I had to find alternative suppliers for my materials (Electrokit for some electronics, In-Time for the antennas, Farnell for the SuperCaps), and some had to be ordered from DigiKey anyway. Try to keep your parts ordered from DigiKey below your country’s import tax threshold, otherwise you might end up paying import taxes like me, which is not fun.

Here is a picture of the PCBs from OSH Park, which are of excellent quality. More will come once I receive the SuperCaps and start soldering the cellphone.

Cellphone PCBs from OSH Park.

Cellphone PCBs from OSH Park.

Master’s Thesis: Improved traffic safety by wireless vehicular communication

I have recently completed, presented, defended and passed my master’s thesis project. It was a great experience which I believe has the potential of preventing traffic accidents and saving human lives. Bellow you can read the abstract and if you are interested you may download the whole report here:


In tomorrow’s vehicle industry vehicles will have the ability to communicate and cooperate with each other in order to avoid collisions and provide useful information to each other. However, for this cooperation to be possible all vehicles will have to be equipped with compatible wireless 802.11p modules that implement the ITS-G5 standard. During the implementation phase of the system there will be plenty of older vehicles without such equipment.

This thesis addresses this problem by developing the hardware and software for a road side unit called Drive ITS. It consists of a universal medium range radar that detects older vehicles, a 802.11p modem that forwards their position and speed vectors to newer vehicles and an embedded system that utilizes and integrates those two parts.

The hardware for the embedded system is divided in two main parts; a microcontroller board and a single-board microcomputer. The software is written in two programming languages; C++ for the microcontroller and Java for the microcomputer.

Tests have been performed by comparing Drive ITS results to results from other vehicles that already implement the ITS-G5 standard and it has been confirmed that the system works as it was intended to.

This solution will prevent potential accidents of newer ITS-G5 vehicles with older ordinary vehicles thus saving human lives.

RFID tag emulation with an AVR

Some time ago I read this article about using an AVR ATtiny85 microcontroller to emulate an EM4102 RFID tag and today I thought of giving it a try.

I used an Arduino as an ISP programmer to program the ATtiny85 with this source code. The electronics used:

  • 1x AVR ATtiny85
  • 1x 10uF capacitor
  • 1x 22uF ceramic capacitor
  • 1x Home-made coil from toilet paper cardboard

Here are some pictures and a video from the result:

Continue reading