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ZWO ASI 120 mm very low frame rates


red dwalf
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some of you may be aware that my frame rates using sharpcap 2 and firecapture latest version have been rubbish, only slightly over 1 fps,


now last night i thought i would give it another bash, computer not camera, so i unplugged all of the usb devices on the desktop pc, plugging in the camera and had frame rates of over 250 fps in a fairly good size image frame, i thought i`m onto something here, a usb device must be causing the problem, one at a time i plugged in the usb devices and tried firecapture after each item plugged in, keyboard already plugged in of course, then eqtooth, no problem, xbox wireless reciever, no problem, powered usb hub, PROBLEM ! frame rates would hardly go over 1.5 fps unless i had the image window on 120 x 120, the usb turbo slider was turned down to it`s lowest i.e. 40, even with the hub unplugged it struggled when increased the usb turbo slider, image starts to jump around.


now i`ve found the culprit, what can i do to reslove the issue ? all the ports are usb 2 so it says on the manufactures website.


it seems to make no differance if the usb 4 port hub is turned off at the mains or on,


any of you computer boffins have any help or fixes the could tell me about.


by the time i had finished this investigation it was 2am in the morning so still have no images of Jupiter ! 


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It does say on the ZWO site "Full resolution function of the ASI120 requires full 480mbs USB communication" - that's not USB 2 and certainly not a shared USB port . In practice about 30 MB/s for USB 2.0 and potentially 400 MB/s for USB 3.0.


 


Obviously higher frame rates = more data being thrown down the USB pipe. Which if shared will slow it down and I guess the drivers slow themselves down to find the optimum rate.


 


As Leigh says have you tried another port on your PC - All USB devices/hubs are hardwired to a USB controller and if you have 3/4 ports chances are there are more USB controllers (say two on each). You can see this via Device Manager.


 


Can you try the Cam on its own USB port (Not HUB) and everything else on the powered Hub to see how that works.


 


You may also being exceeding the power rating even though you have a powered hub - don't know your spec so hard to say.


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Is it the same on all the USB ports on the desktop? Do you have another hub you could try?

not tried the hub on any other usb ports on the computer, can this make a differance ? there are a group of 4 on the back of the pc which i believe are a on a pci card, there are two more on the front below the start button and one more fitted into a drive bay of the pc with other card slots.

i don`t have another hub i can try, until now this one has worked fine, but i know very little about them. 

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Dlink Web site says "For comparison purposes only. Maximum transfer rate based on USB 2.0 specifications. Actual data throughput will vary." In other words you will never get 480mbs rate thats there get out clause.


 


Felix uses the same camera(might be Colour) how does he connect and what is his rate!


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It does say on the ZWO site "Full resolution function of the ASI120 requires full 480mbs USB communication" - that's not USB 2 and certainly not a shared USB port . In practice about 30 MB/s for USB 2.0 and potentially 400 MB/s for USB 3.0.

 

Obviously higher frame rates = more data being thrown down the USB pipe. Which if shared will slow it down and I guess the drivers slow themselves down to find the optimum rate.

 

As Leigh says have you tried another port on your PC - All USB devices/hubs are hardwired to a USB controller and if you have 3/4 ports chances are there are more USB controllers (say two on each). You can see this via Device Manager.

 

Can you try the Cam on its own USB port (Not HUB) and everything else on the powered Hub to see how that works.

 

You may also being exceeding the power rating even though you have a powered hub - don't know your spec so hard to say.

thanks for the help, how can i see the usb info in device manager ? i know where to find the ports but what am i looking for ?

i`ve also tried the camera on it`s own usb port, not plugged into the usb hub at all, running it totally separate, runs fine until i plug the powered hub into another usb port on the pc, both items using separate usb ports but when both plugged oin then the problems start.

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The ones on the front of your PC may well connect directly to the Motherboard USB chips so might be worth a try. As always try things one step at a time - as you did above  :)


 


So plus the Cam into one port next to the drive bays and the powered hub into a usb port connected to the PCI card - worth a try.


Edited by stash
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Dlink Web site says "For comparison purposes only. Maximum transfer rate based on USB 2.0 specifications. Actual data throughput will vary." In other words you will never get 480mbs rate thats there get out clause.

 

Felix uses the same camera(might be Colour) how does he connect and what is his rate!

USB 2 runs at 480 megabits.

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The ones on the front of your PC may well connect directly to the Motherboard USB chips so might be worth a try. As always try things one step at a time - as you did above  :)

i`ve also tried the usb powered hub plugged into the rear usb port on the pc and the camera into the front usb port on the pc and exactly the same thing happens.

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USB 2 runs at 480 megabits.

Sorry to disagree it doesn't in practice - and certainly not when shared  :)

 

"USB 2.0 was released in April 2000 (now called "Hi-Speed"), adding higher maximum signaling rate of 480 Mbit/s (effective throughput up to 35 MB/s or 280 Mbit/s)"

 

Anyway it doesn't help Rob  :)

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The bus speed is 480 mbps. What you actually get will vary on what you have connected. I only pointed it out as you used mbps and MB/s in the same paragraph and not everyone is aware of the difference.


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Rob - do you have a normal (unpowered) hub with active usb cables? My thinking is you are dealing with very short distances in your obsy so it may not be necessary to use a powered hub. You could at least try it out and see if it works. I looked at the spec of your powered hub and I agree with Leigh - it says the data rate may vary. :)


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The bus speed is 480 mbps. What you actually get will vary on what you have connected. I only pointed it out as you used mbps and MB/s in the same paragraph and not everyone is aware of the difference.

Must be a bad USB day - just been out to a client with a USB problem.

 

No problem Leigh and I totally agree with your suggestion - Rob needs to get/try another Hub that is probably his best option  :)

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i haven`t kim but i did try it with the power on and off to see if that made a difference but it did not, only thing that seemed to fix the problem was if i disconnected the usb hub from the pc altogether,


could it be a driver problem ?

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Rob , Dlink are normally fine it could be just be one on the "blink". Trouble is most are rebadged and all come from China - not that I am saying Chinese M/F is bad.


 


Is there no one in EMS local that can lend you hub


Edited by stash
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I doubt very much it's a driver problem Rob - could well be hardware as mentioned above. Personally I would ditch it mate and get one guaranteed to work with astro gear.


 


The one at the bottom of this page would be my recommendation: http://www.astronomiser.co.uk/converters.htm


 


(It's always worth paying a couple of quid more for something that has been tried and tested) :)


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I would always plug the camera in its own usb and not a hub (if I can)


 


I get something like 150fps with mine on the ancient sony laptop


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Thanks steve, but the camera is plugged into its own port totally separate to the hub, the power on the hub isn't even turned on but when its plugged into its own port on the pc the camera suffers poor frame rates, even though they are both using totally different usb ports, as soon as the usb hub is unplugged the camera works great.

Doesn't add up to me.

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