Hi,
On Jul 15, 2011, at 9:23 AM, Simon Wilks wrote:
> Hi,
>
> I picked up an XAircraft X650 recently and just finished building it and gave it a first test flight. Very nice :) Here is a brief build log if you are interested:
http://sites.google.com/site/paparazziuav
Nice page, I hope you will get your Aspirin soon! :)
> I have a Lisa/L board and was planning to adapt the X650 for it. I was initially thinking I would need to at least replace the ESCs with I2C controllers but I was wondering if the Lisa/L (code) supports driving ESC controllers.
Yes it does. There is a PWM supervision module there.
> I understand one of the problems with ESC is it is too slow but XAircraft seems to have come up with something new that provides 500Hz control. Here is a link to an article on the UltraPWM protocol and the reason they stayed away from I2C:
http://www.xaircraft.com/wiki/UltraPWM/en
We are running all our aircraft on PWM based ESC's. Most china motor controllers will accept higher frequency PWM input then the nominal 50Hz, 200Hz was enough to get a stable Quad and 400Hz makes it nice and smooth. In my opinion I2C is evil, error prone, unreliable and a single point of failure. PWM or PPM is much more robust to EMF. I2C was designed for short connections between components on one single PCB not to run through half a meter of wire. I personally had lot's of headaches associated with I2C in the past.
The only even better solution would be CAN. (lisa/l supports CAN but the only motor controller that has CAN support at the moment is http://open-bldc.org and it is sadly still not production ready, yes it is my fault ... I still did not clone myself to have enough time to finish it :/ )
But enough of the rant. Yes Paparazzi and Lisa/L supports PWM based motor controllers and yes it also supports high frequency PWM. So go for it and use it! :D