maximum analog readout rate?

Posted by Michiel Demey at January 28. 2008

Hi,

I connected a Sharp IR sensor (GP2D12) to the controller and reading it out in Max/MSP (on MacBook Pro) using the USB object, but it seems that I get a maximum readout rate of about 80Hz when I count the number of samples received per second.

I tried both the autosend and the manual reads using a metro as a trigger. When I go down to a 13ms interval it seems to work ok, but when I go down to 10ms I still get around only 80samples/s and this number seems to vary.

Does anyone have an idea where the bottleneck might be? Is it the usb object, Max itself or the firmware in the controller?

Thanks

PS: from a post http://www.makingthings.com/forum/development/timed-analog-acquisition-how-fast/ I get the feeling it is not the firmware, but more Max or the usb object. they report 50'000 samples/s which would be great for me (but then using Max)!

Re: maximum analog readout rate?

Posted by Liam Staskawicz at January 28. 2008

Hiya - I know of a problem in the mc.usb external (it may already be fixed even in SVN, I can't remember) that prevents it from reading faster. With the fix, I've had it reading down to about once every 3ms. This is about as fast as I'd expect it to go with the current firmware. If you want to contact me via email I can send you a working copy (no promises!) - liam at makingthings dot com.

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