A begin with the stm32


I had some trouble with my computer and I was not able to compile ChibiOS. Too much time losing because of some library missing.

Problem now fixed, and that allowed me to make my first flash on the olimex card, and also to make a thread to control LED.

A beginning for our PCB


today we finished to define the list of components we need for our new ball. Among these components, there is an extern wifi antenna, that is not very cool, but we think that the set of LED could be a Faraday Cage and prevents our ball from any wireless connexion.

Then we tried to design our PCB, beginning with CPU, and we realized that is very difficult. Indeed the function of some pins in the CPU are not clear at all for us, while the datasheet considers them as classical and don’t help us. It makes us not efficient and very slow to work, but the more we find it hard, the more we learn.


Why StabiloRose is better

Today, we have changed the main purpose of our initial project migB. The reasons of this change and the new purpose are explained below by Natolumin. Indeed we were going to use too much sensor and effector, that makes our project much harder as soon as we have to think about the function of each component, if they are really useful, and how to put them together. It could be diappointing to change our project like that, but research we have already done about component and mathematics algorithm will still be very useful.

StabilityRose will use mainly LED and IMU. We think to use about 3 hundred of LED onto a ball of diameter 16 cm. We also intend to use an internal opaque ball so that users will not see inside it. The LED will be arranged like an orange peel. For this reason the main new challenges are as follows : to control the set of led as we want, knowing this set is an orange peel, and to control perfectly the orientation of our ball so that text displayed stays horizontal.

Actually mathematic problems are much harder than the initial project but we have less components and a more accurate way to follow. Therefore this project become easier from a certain point of vue



today we begin to define some PSSC for our balls project migB, and begin to think about components we need. According to our teachers, it is very hard to analyse a motion system with an IMU, that’s why i did research about it. It seems that orientation sensing is very easy, while getting velocity and position is much harder. Indeed getting velocity and position requires at least one mathematical integration. So if you get an error on acceleration, even little, and you always get a little error at best, this integration which increases the error. Therefore it is impossible to be very accurate over time. But how much do you want to be accurate ? This is very difficult to foresee which algorithm you will need to get what you want with your IMU, as soon as your project is such specific. Until now the only good one i found is the Kalman Filter, but i’m afraid that our errors could be negligible and thus Kalman Filter would become a big algorithm for nothing.

Also i installed Archlinux on the last computer available to us.

Balls coming soon


in the last two days we chose a name for you projet, MIGB, which means Many Interactive Games in a Ball, and begin a wiki to descript it : what do we want that the balls do exactly ? We still search new idea.

Moreover i achieve to install archlinux on my computer, with the help of other members of rose2015 (and web of course). I decide to do not use any other OS on my computer, so that it prevents me from escaping difficulties.

IMU and Accelerometers

Although projets have not been chosen yet, and even if new project are emerging, it seems some of us will need to use an Intertial Measurement Unit. That’s why we have to make a specific tutorial about IMU. As the subject is specific, documentation is harder to find.

Today i mainly focus on this tutorial and precisly on accelerometers in an IMU. It is hard to get specifications of those accelerometers and the reasons are as follows. There are a lot of different types of accelerometers, so there are some specifications which can be very interesting for one particular type, but much less interesting for another. Besides, each author pays attention to specifications that he finds important. And lastly it seems there are no standard about the words you can use for specifications. It means that seller can use the words they want.

But I am sure that more research will overcome it.