Wednesday, September 24, 2008

Between Theory & Practice

Today I found back an old article I had written for a few friends of mine a few years ago while working as R&D software programmer and wanted to share the story again as it remains pretty much true and applies to other fields of IT as well.. Do not worry; you do not need to have a master in advanced telecom technologies to understand what is written below.

Back then my job consisted to design and implement a communication bus (SMBus); in other words think telephone line as it is easier to understand. This digital bus was composed of 2 wires: the clock wire and the data wire. The following devices were connected on the bus: a PC, a laptop battery (yes, you can talk to a battery, the very same battery you have inside your laptop and believe me it will answer you), and a power supply control card with a microcontroller (MCU) and a small memory chip on it. All these 4 devices had their own bus address (think phone number), and they were able to call each other in order to send and receive data (like talking on the phone or sending a fax). Last detail, all these components were grounded (linked to the ground) for electrical security reason. The theoretical schematic of the bus looked like this.

Didn't it look so nice on paper ?

In order to check the data transmissions and receptions (ie, monitor the communication), I had also connected an oscilloscope on the bus.

Now, the reality was slightly different and the result I obtained looked rather like this:

Tell me you got scared by reality.

But don't trust Murphy's Law on this one as it actually worked. This being said, I am confident you will feel reassured by knowing that similar busses are present inside your computers, your car, the trains or the planes you take, and so on.

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