[Xenomai-help] Advice for a newbie on Xenomai & USB

[Xenomai-help] Advice for a newbie on Xenomai & USB

[David]

Hello,
 
I am a PhD student at the Technical University of Catalonia. I work on 
UAV helicopters. It is a new field in my research group so I need to 
develop the rig before start working on Identification and Control 
Theory (which is supposed to be THE topic of the Thesis).  
 
We chose to use en embedded PC as 'brain'. The readings of the system 
come from an IMU and the actuators (R/C servos) are commanded by a 
microcontroller (already programmed and working). Both devices Tx/Rx 
input/output data with the computer through TTL USART converted to USB.
 
The PC is an Intel Atom Z520, on a chipset ..., with 1GB of RAM and 
booting on a high-speed Compact Flash.
 
On the first stage of the software, a human is choosing the 
microcontroller inputs (that is: piloting the craft), and the computer 
'only' needs to gather the input to the microcontroller and the output 
from the IMU and write it to disk with due time stamps. 10Hz would be 
OK, 100Hz would be the goal.
 
On the second stage, the computer will have to gather the output data, 
compute the control input and send it to the microcontroller. On hard 
real time at (>10 to 100) Hz, of course.
 
As you may guess, I chose Xenomai to make sure time requirements are 
respected. It would run on a command-line Ubuntu 9.04. The programming 
would be developed for C++ (compiled with g++).
 
As a totally newbie on Xenomai and only average user on Ubuntu-Linux, I 
would need some community guidance to get my feet wet.
 
As you already know my specifications, do you think the computing system 
is suited for the needs? As the computer does not have embedded USART 
modules, I rely on USB to TTL USART converters (ttyUSBx). Are there any 
suitable drivers for Xenomai? USB4RT? With interruptions and 
configuration for SSP?  
Where do you guess the bottlenecks will be?
Is there any detailed guide for newbies? Could you suggest me any 
documentation on PC architecture and/or Linux OS to fully understand the 
system? I have mainly programmed microcontrollers, on which I would make 
use of interruptions and input/output modules all the time, and I need 
to port it to PC, for which I have never used interruptions nor used the 
input/output modules' drivers deeply nor write them.
 
Any suggestions would be very useful.
 
Thanks for your help.
 
Best regards,
 
David Lavèrnia  
 
 

Re: [Xenomai-help] Advice for a newbie on Xenomai & USB

[Wolfgang Denk]

Dear David,

In message <4A67F5D2.4090708@domain.hid> you wrote:
>
> As you already know my specifications, do you think the computing system
> is suited for the needs? As the computer does not have embedded USART
> modules, I rely on USB to TTL USART converters (ttyUSBx). Are there any
> suitable drivers for Xenomai? USB4RT? With interruptions and
> configuration for SSP?

Could you use a PCI or PCIe card with standard 16550 UARTs instead?

I recommend to get USB out of the link here.


Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@domain.hid
You cannot propel yourself forward by patting yourself on the back.

Re: [Xenomai-help] Advice for a newbie on Xenomai & USB

[Wolfgang Denk]

Dear David,

In message <4A68283F.6030304@domain.hid> you wrote:
>
> What happens if I cannot get USB out of the loop? Is it doomed?

Well, in my experience (> 10 years of embedded Linux) USB has an
unchallenged number one position on the list of candiates for causing
problems in embedded projects - without any real-time requirements.

If you cannot get rid of it, then I recomment to run thorough tests as
early as possible.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@domain.hid
Experience is what causes a person to make new  mistakes  instead  of
old ones.

Re: [Xenomai-help] Advice for a newbie on Xenomai & USB

[David]

Dear Wolfgang,

What steps would you recommend me to follow that arduous path?
What drivers, manuals, guides, books would you suggest to get started?

The PC I'm using, in addition to the 6 USB's, it also has Wlan, Lan,
mini-SD, and IrDA. Do you think it would be better to use those modules
to Rx/Tx info?

Thanks for your help.

Best regards,

David


Wolfgang Denk wrote:
> Dear David,
>
> In message <4A68283F.6030304@domain.hid> you wrote:
>   
>> What happens if I cannot get USB out of the loop? Is it doomed?
>>     
>
> Well, in my experience (> 10 years of embedded Linux) USB has an
> unchallenged number one position on the list of candiates for causing
> problems in embedded projects - without any real-time requirements.
>
> If you cannot get rid of it, then I recomment to run thorough tests as
> early as possible.
>
> Best regards,
>
> Wolfgang Denk
>
>   

Re: [Xenomai-help] Advice for a newbie on Xenomai & USB

[Wolfgang Denk]

Dear David,

In message <4A685ACF.4050703@domain.hid> you wrote:
> 
> What steps would you recommend me to follow that arduous path?
> What drivers, manuals, guides, books would you suggest to get started?
> 
> The PC I'm using, in addition to the 6 USB's, it also has Wlan, Lan,
> mini-SD, and IrDA. Do you think it would be better to use those modules
> to Rx/Tx info?

Well, using RTNet on your LAN interface is probably a lot easier and
definitely more reliable than a serial link over USB...

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@domain.hid
Never underestimate the bandwidth of a station wagon full of tapes.
                                -- Dr. Warren Jackson, Director, UTCS