Saturday, January 3, 2015

My Development Environment on the Raspberry Pi


I have been playing around the the Raspberry Pi for a while now, doing basic projects to get the hang of it. These projects have been very simple so far, not even worth blogging about them, but I found myself recreating the same (or very similar) environment on the RPi every time I started a new project. The reason I start from scratch every time is to learn all the special settings/setups a specific project requires.
My RPi used for development.

I, however, found, that I can't remember ever step and I keep researching the same thing on the internet over and over again. So I decided to create this article to serve me (and possible other beginners) as a collection of setups steps for different kinds of projects. This article may grow in the future as I progress, so I expect it to contain some advanced stuff as well later on.

Saturday, December 6, 2014

First Experiences with the ESP8266


The latest "craze" among embedded electronics engineers is the tiny chip called ESP8266. It's a low cost, low power, high performance chip allowing wireless connectivity with your wifi network. In the following I would like to share my experiences setting up such a module for the first time.

The module is barely larger than a 1 euro coin.

Monday, August 25, 2014

Repurposing a Laptop screen as a Universal Test Display Rig


Although I am fairly well set up for working with multiple computers on a single monitor (using a 4 channel KVM switch), from time to time I have an extra equipment, be it a PC, laptop, or any other consumer electronic device that needs a display to interact with it, that is always a pain to hook up with a monitor or TV for trouble shooting. As I recently had success experimenting with LCD panels salvaged from old laptops/TVs, I decided to make a permanent test rig for such occasions.
Finished look

Wednesday, July 23, 2014

How to Recover a Laptop After a Failed BIOS Update


A few days ago I managed to brick my Compaq Mini 311 netbook by mistakenly flashing the wrong BIOS image. The computer only switched on the CPU fan for a moment when I pressed the Power on button, then it switched off, nothing worked, no lights were on.

Since the netbook was working perfectly well before the BIOS update I immediately knew that the wrong BIOS image was at fault. However, flashing the correct image required the netbook to start up correctly in some kind of an operating system, which, without a proper BIOS, is not possible. Not even the Win+B combination worked.

Luckily, not all is lost, as all it needed was a correct BIOS, which I could easily download from the manufacturer's web site.

Yes, it's a Compaq Mini 311 netbook. I prepared a replacement chip loaded with the correct BIOS. Later it turned out that the original chip was not destroyed by the procedure I put it through.

Once I had to open the laptop to fix it I decided to take this opportunity to explore the options there are for fixing the broken BIOS and compile my findings in this article. In the process I tried all of the methods described below, some on the actual laptop I fixed eventually, some on (really-really) dead motherboards.

There are several ways of getting the right BIOS back in the computer - in the following I am going to present a number of ways to get your laptop back on its feet. There are probably more ways to do it, but this should be a good starting point for someone in the same shoes as I was.

General information

Most fairly recent laptops have their BIOS in a serial EEPROM with an SPI interface on the motherboard. Its location varies, but since it is the only EEPROM on the motherboard, after a few minutes of visual inspection it is easy to reveal it. In some laptops it's covered by a black sticky tape which needs to be removed temporarily to get access to the chip. These EEPROMS are usually 1024kB (1MB) or 2048kB(2MB) in size. They come from various chip manufacturers, like Winbond, STM, Microship, etc. Not to confuse with BIOS (firmware) manufacturers, i.e. Phoenix, AMI, Award, etc. The product number is printed on the chip and is something like this: 25xx80 (1MB) or 25xx160 (2MB). There may be some extra letters in the front or at the end that are all important when you select a replacement chip, but for the purpose of finding the chip on the motherboard they are not relevant.

Thursday, June 26, 2014

WiFi Repeater Rescue


I have been using a cheap, no-name wifi repeater in our house for about a year. It is of the type that you plug in a mains socket on the wall (after configuring it with a computer) and you forget about it. It's done a good job (i.e. zero maintenance) until a few days ago, when one day I realized it was not working. Only its red power LED was blinking, and we all know the red lights, especially blinking ones mean no good.

The two antennas are stuck to the back of the front panel.

Since it's a cheap model, I immediately ordered a new one, but it would take several days to arrive, so I decided that before throwing it away, I would open it up and see what's inside, how it works, and maybe salvage some of the internals for later projects.