As I developed the device, from idea to production. Part 3

So the technical part of the project MT9000 , the final. If you have not read the first and second parts, I recommend to read. Well, let's get started!

As a mother learns to wash her hands before eating, so planning is an obligatory stage in the development of any project. Otherwise, the project can turn into a process, but I absolutely do not need it. Without a plan and definition of development methods, I do nothing!
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To develop the project as a whole, the good old classic incremental approach was used: careful planning, design, several stages of prototype testing, release. It is necessary to plan in advance all the critical dates and important points of the project. Then there is a chance to pass the project with a minimum delay.

Serena OpenProject will help us present a project plan.



With the development of software, the situation is a little different. Although the project is generally small, but for the development of software we actually take into account the XP methodology, taking the best from it and not going into religious wars on trivial matters such as team composition and planning games. The approach I developed for such cases is as follows:
- The main skeleton of the program;
- frequent internal releases;
- continuous testing and identification of bugs;
- collective ownership of the source code;
- As a representative of the customer, I speak myself.

For the development of the HW part of the project, the Eagle cross platform package was used. The trimmed free version was enough. In the future, I think I should buy the full version, after all, the price tag for a license for this product is quite humane. In Eagle, there are no advanced tools, such as automatic trace of printed circuit boards, but for a project of this level it is not necessary.



To start writing software, so as not to wait until HW prototypes are ready, several debugging Evaluation Board sets from selected manufacturers, worth less than a thousand dollars, were purchased.



In accordance with the main cascade plan, the project produced approximately three iterations of correction of printed circuit boards of the base unit and several iterations to modify the sensor boards. Each square millimeter is worth its own penny, so we try to do everything as compact as possible.



As we remember, the project we use wireless technology. In the beginning, I was hoping that it would be possible to simply write software, without going into the details of wireless communications. That is, at the level of functionality provided by the library manufacturer. However, this turned out to be a profound delusion. At the moment when the network starts to fall, and you do not understand why this is happening, an insight has come that you cannot do without a wireless sniffer. I had to quickly look for special tools for analyzing wireless traffic.

There is such a network traffic analyzer, it is called WireShark. An elegant solution was the idea of ​​Jennic to create a software and hardware tool that will emulate network traffic, substituting unique headers into it for personal identification. A hardware-based wireless sniffer was made quickly on the knee of one of the first ready-made sensors of the future project.



We connect the WS sniffer to the USB of the computer and start the traffic from this wireless sniffer to the additional loopback interface we created.

Next, we ask Wireshark to display traffic from this loopback interface and enjoy the pictures of what is happening on the air.



Naturally, Wireshark can be used to analyze any type of traffic.

I do not have the opportunity to dwell in detail in the story about software, since it is the subject of know-how of the company in which I work, I can only say that software is one of the most important components of the project. Without the participation of good programmers in the project, nothing would have happened. Thousands of lines of code were written, tested and corrected, and a total of 700 hours of hard work was spent.

Returning to the question of the first part, as promised, I publish a picture of the distribution of channels and the interference of 802.11.b and 802.15.4. To minimize the impact on the quality of communication from the WI-FI side, we write software so that it selects the channel 15, 20 or 26 for the operation of our system.



That's all that I would like to tell you about the project for the development of MT9000.

As a result, spending about 8 months. time and, in general, a small investment, we have created our own device that uses modern wireless technology, which is on guard of human peace of mind. Our device is completely ready and is on the virtual shelf of the virtual online store, and you can also buy the MT9000 on real shelves. Now we are working on other interesting projects, and all our products can be found here .
Anyone who wants to repeat my experience, I wish you good luck and success in work. Dare!