Hi,
I connected a mechanical device to 1 of the USB A ports and this device has a PID update rate of 1 kHz. Instead of make a nice movement as it did on a pc, it started to oscillate. I searched for update rate info in the board manual, but found nothing. Can anyone tell me what the USB A update rate of the board is ? Or the turn around time ?
Thanks.
Under Linux?
Yes, under Ubuntu Linux 13.04, to be exact.
Do you use a wall adapter or a usb port to power the board?
I’m using a wall adapter, since as stated in the manual, otherwise I can’t connect anything to the USB ports like that device or keyboard, mouse or cam.
The USB Host ports works fine on USB power, as long as the current is demand is low. To support higher current devices, you need to run it on DC power.
Gerald
Like I responded to lisarden, the board is powered by a wall-adapter so it runs on DC power. Also, what I forgot to mention is that the mechanical device is powered by its own DC power. So the question is still what the update-rate or turn-around time of the USB-A bus on the board is.
I don’t have an answer for you.
Gerald
Too bad. Thanks anyway.
To hvn052:
You have not connected a mechanical device to an USB port....
You have connected a device which has mechanical and electronic parts to the USB port of the Beagle Bone.
And you have in the PID loop, software that runs on the Beagle Bone.
All the USB timings are known from the USB specifications, but as you have your software in the loop, asking someone on the Internet what is the update rate of your software, seems very wishful thinking.
Please try an oscilloscope.
Best regards
Paulo Ferreira
Hi,
I connected a mechanical device to 1 of the USB A ports and this device has a PID update rate of 1 kHz. Instead of make a nice movement as it did on a pc, it started to oscillate. I searched for update rate info in the board manual, but found nothing. Can anyone tell me what the USB A update rate of the board is ? Or the turn around time ?
Thanks.
To hvn052:
You have not connected a mechanical device to an USB port…
You have connected a device which has mechanical and electronic parts to the USB port of the Beagle Bone.
And you have in the PID loop, software that runs on the Beagle Bone.
Not the BeagleBone…the BeagleBoard-xM.
All the USB timings are known from the USB specifications, but as you have your software in the loop, asking someone on the Internet what is the update rate of your software, seems very wishful thinking.
I agree with you on the USB specifications. However, my point is that I ran the same software on both a normal computer and the BeagleBoard. On the normal computer everything works fine while on the BeagleBoard-xM the device starts to oscillate. Back to the normal computer, it works fine again. Now assuming that all LS/FS/HS USB specifications are the same, how can this happen? Any suggestion on what I can be missing that is not the same ?
Please try an oscilloscope.
That’s a good suggestion. Have to find one.
hvn
............................
I agree with you on the USB specifications. However, my point is that I ran the same software on both a normal computer and the BeagleBoard. On the normal computer everything works fine while on the BeagleBoard-xM the device starts to oscillate. Back to the normal computer, it works fine again. Now assuming that all LS/FS/HS USB specifications are the same, how can this happen? Any suggestion on what I can be missing that is not the same ?
Please try an oscilloscope.
That's a good suggestion. Have to find one.
hvn
Well, between a "normal" PC and a BeagleBoard, the "only" things that change are: the compiler, the processor's architecture, the processor's clock speed, the memory interface, the caches, the peripheral's connection to the processor and the interrupt architecture.
If you are expecting no influence from those changes, you need to wake up. 
Best regards
Paulo Ferreira
…
I agree with you on the USB specifications. However, my point is that I ran the same software on both a normal computer and the BeagleBoard. On the normal computer everything works fine while on the BeagleBoard-xM the device starts to oscillate. Back to the normal computer, it works fine again. Now assuming that all LS/FS/HS USB specifications are the same, how can this happen? Any suggestion on what I can be missing that is not the same ?
Please try an oscilloscope.
That’s a good suggestion. Have to find one.
hvn
Well, between a “normal” PC and a BeagleBoard, the “only” things that change are: the compiler, the processor’s architecture, the processor’s clock speed, the memory interface, the caches, the peripheral’s connection to the processor and the interrupt architecture.
If you are expecting no influence from those changes, you need to wake up.
Oh, I’m wide awake and do know it’s a RISC board and thus different. But despite that, an ordinary mouse, keyboard and webcam work well. if you consider Sparc (RISC as well)…not an “ordinary” computer either, but mechanical devices are proven to work. So being different in architecture doesn’t mean it can’t or won’t work. Still looking for an oscilloscope.