Interactive web site of Télécom ParisTech's ELECINF344/ELECINF381 Robotics and Embedded Systems classes (a.k.a. ROSE, 2012 session).


PCB and RoseAce

First, I finished the PCB for the STM32 board.

Then, for our project, we have chosen the general architecture: the board embedded on the propeller will contains a cortex A8 and a FPGA. Indeed, benchmarks I have found about ffmpeg, the library we will use to convert MPGE2 (or MPEG 4) received thanks to the wifi connection use about 80 % of a A8 cortex. The wifi will use about 5%. So, we can not use the A8 cortex to command the LED drivers.

The question is the following: we can chose working with a armadeus (http://www.armadeus.com/english/products-processor_boards-apf51.html) but we have to design a main board with wifi and, we will only begin to work when the main board will be ready or, we can use a gumstix (the same that we used for previous test) and we have to chose the FPGA and to design the main board with the FPGA but, we can start working on the gumstix now.

Finally, I think about the LED driver we have to use and, the LED board architecture. We decided to use 8 different bus to command the LED driver so, LED will be divided in 3 groups on each propeller. The frequency needed is about 10 MHz for each LED driver. The LED will be command with a PWM signal created by the LED driver.. A LED will have a frequency of about 15 kHz so a PWM frequence of 33 MHz will allow us to chose correctly the LED intensity.

Jeremy Sauget

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1 comment to PCB and RoseAce

  • Yoann

    Concerning Armadeus, we used an APF27 last year, it’s not bad in itself and has the big advantage that the CPU/FPGA communication is already working. But one big drawback is documentation – at least last year it was. It’s miles away from what you’ve seen with the STM32 datasheet. If you did not do it already, I suggest you take a look at what they call a “datasheet” and at the wiki they use as documentation. Check things that are “under construction” or “coming soon” (like audio in), or obsolete. There can be some contradictions between several pages of the wiki and the few example codes given, too.
    Also, I think you can install a standard Arm Linux distribution and use a package manager on a gumstix, while you need to compile a rootfs with buildroot on the Armadeus (at least on APF27 we needed it). It’s not that hard and at least you learn how to do it, but it can be a bit painful to add new packages (we specifically suffered with third-party C-python modules).

    We finally made it work, that’s not the problem, but sometimes you have the impression to waste hours on something you could do in five minutes with a clean documentation.