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


Rose Ace : My computer is running at 1000rpm

Today we make an experiment with the Gumstix. Our problem was to know if in turning at 1000rpm in a ventilator the WiFi will work correctly.

The first was to get a wireless power source to the Gumstix.

We got a lot of problems with that. First of all, the power connector of our Tobi expansion board is damaged (thanks to Copterix :o ) which cause a lot of reboot at any movement… We solved this with a lot of gaffer.

Secondly our hacked connector (with sticky tape) for the battery was not very well either and caused some trouble. Thanks to the PACT project which order a lot more than necessary 9V battery connector we improved our power line.

And last problem for the power, our board was rebooting in loop before we had a chance to login in… Simple problem but hard to guess, our battery didn’t deliver enough current. It was easily solved with a second battery in parallel.

Now, add a lot of gaffer to secure into place the batteries, the Gumstix and the antenna and we’re ready.

Of course, Murphy’s law requires, at this exact time the Gumstix decide to no longer properly boot and the WiFi to stop working. But with a little of black magic that finally worked and we have done our tests.


Our ventilator was missing of power and can’t get to its maximum speed (~1100rpm) with our board mounted on it (we could do better with a better balancing of the weight). But at the speed that we reach we succeed to had no loss of bandwidth (to confirm with a faster ventilator) which is a good news.

The bad news is that even placed on a table at 20cm from the computer we can’t do better than 1.5MB/s of transfer rate in WiFi (and 3MB/s in ethernet…) which is some kind of disappointing.


Possibly related posts:

  1. STM32, communication challenge and works on the Gumstix
  2. Rose Ace : Architecture choice & distribution of work

12 comments to Rose Ace : My computer is running at 1000rpm

  • What did you use to measure the transfer rate?

  • flx

    We have done a scp from a computer to the gumstix.
    Maybe the default Linux Angstrom in the internal memory is in cause too. Anyway the Gumstix is still in place in the ventilator and now that it is working we will try to do some better tests tomorrow morning.

    • So what you are measuring is also the ability to uncrypt the data on the Gumstix, as well as the flash write bandwidth. Wow. If you want to measure the TCP bandwidth, please do a test that only measures that.

  • flx

    We’re sending to /dev/null so I hope it’s not writing in the flash but that right for the encryption.
    We’re trying to do a better test but the WiFi no longer wants to work properly (with the same config that yesterday…).

  • How did you manage to solve that rebooting problem? I am having the exact same issue. Also have you noticed any issues with the HDMI output?

  • flx

    Hi !
    We got many problems at once so we’re not totally sure of what solve what but for us the rebooting problem was an energy problem. So maybe your battery do not deliver enough current or your battery is over discharged.

  • sylvain

    We suspected that reboots came from the lack of power delivered by batteries. With a second battery in parallel we haven’t had this problem any more.

  • sylvain

    Sorry for the double answer. And we haven’t used the hdmi output yet.

  • Well I am powering mine from the USB port on my laptop which (if I’m not mistaken) delivers 1A at 5V which is the same as the power adaptor sold by Gumstix. Are you guys using 2 9V batteries?

  • flx

    Yeah we’re using two 9V battery to make our gumstix working properly.
    Maybe your USB port do not deliver the theoretical current ?

  • Yea maybe…guess I’ll give the batteries a go then. Thanks!

  • flx

    Euhhh and the limit current for the USB is not 500mA rather than 1A ?
    Whatever, if you have a power adapter under the hand try it.