Connecting multiple ZWO cameras

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wcblack7
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Connecting multiple ZWO cameras

Post by wcblack7 » Fri Nov 02, 2018 7:03 am

Hi,
I'm running the latest SharpCap Version 3.2.5856.0 on a Toshiba laptop under Windows 10.
The software is great by the way and I am really pleased with it.
I have two ZWO cameras: ASI294MC-Pro and ASI385.
I can connect one of the cameras at a time to my lap top and everything seems to work great.

However, when I connect both cameras, one of the cameras shows up twice at the top of the camera selection list, but both cameras show up under the DirectShow part of the list. I can access both cameras via DirectShow, but only one of them with SharpCap native controls (whichever one gets listed twice). It is not always the same camera that gets listed twice. I was thinking it was the one that I connected to the USB 3.0 port (I have one USB 3.0 port and several USB 2.0 ports on the laptop). However, I'm not certain that is the case (it may be the camera I connect first, but not sure about that either).

Of course the SharpCap native controls are better than the DirectShow controls, so I would like to have both of the cameras listed there, but cannot seem to get that to work. Seems like a bug, but could be user error, since I've just been using SharpCap for about a week now.

I'm attaching the log and some screen shots.

Thank you!
Bill
Attachments
Log_2018-11-01T20_48_11-5560.log
Log file
(44.79 KiB) Downloaded 42 times

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admin
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Re: Connecting multiple ZWO cameras

Post by admin » Fri Nov 02, 2018 12:25 pm

Hi Bill,

that's a bit weird - I have just tested with a couple of ZWO cameras (120MM-S and 174MC) and both work fine. Will try some other combinations later to see if I can find a problem.

What I can see in your log is that the detection of ZWO cameras seems to run twice at startup. The first time it finds the 385MC and the second time (about 0.1s later) it finds two copies of the 294. When I run with two cameras it only scans once, so I am wondering if the two weird things (duplicate camera, scanning twice) are somehow connected.

Do you have SharpCap set up to automatically open a camera at startup? I wonder if that might cause the second scan.

cheers,

Robin

wcblack7
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Re: Connecting multiple ZWO cameras

Post by wcblack7 » Fri Nov 02, 2018 2:48 pm

Hi Robin,
Thanks for the quick response. I don't have SharpCap set to open a camera automatically, but I wonder if it is related to having one on usb 3.0 and the other on usb 2.0.

I took a generic multiport usb 3.0 external hub and connected both cameras to that and it seemed to open both cameras correctly. Unfortunately, neither camera will operate through the external hub that I have.

You wouldn't happen to know of a usb 3.0 external hub that works with ZWO cameras would you? I know ZWO instructs you not to use one.

So, I tried connecting them both to my usb 2.0 ports, since I have several of those on the laptop. Tada! they appeared correctly in the camera menu when I did that and are working correctly. Of course, I get a lot of dropped frames trying to run these high data rate cameras through usb 2.0... time for a new lap top!

I've attached the log file from when I connect them both to usb 2.0 ports on the laptop. Please let me know if you figure out a way that I can have them scan correctly when one is on usb 3.0 and the other on usb 2.0.

Thanks again!
Bill
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Log_2018-11-02T10_35_10-16308.log
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Re: Connecting multiple ZWO cameras

Post by admin » Fri Nov 02, 2018 9:55 pm

Hi,

I looked at the code and the only things that trigger a second scan for cameras are

a) pressing the 'Rescan' menu item and
b) notification of hardware added or removed

It can't be a) in your first log, since you aren't pressing the rescan button, so there must be a notification of a device removal/arrival coming in which triggers the rescan. I do wonder if there are voltage issues in this problem setup - ie when the SDK starts talking to the cameras in quick succession to identify then one of them drops off the USB port briefly due to a voltage drop and the quick drop/re-attach confuses the ZWO SDK or SharpCap.

Do work your way through the USB troubleshooting steps (shorter cables, turn down 'turbo USB', etc) in the link at the top of this forum to see if any help in your USB2/USB3 setup.

I have had USB3 cameras including ZWO working with a USB3 hub, but I find that the speeds are slower and you have to keep the cable lengths either side of the hub down to 2.5m or so max. I find a single run of USB3 cable longer than about 3.5m to be unreliable too.

cheers,

Robin

celkins
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Re: Connecting multiple ZWO cameras

Post by celkins » Sun Nov 04, 2018 2:19 am

Robin, Bill,
this rescan can readily be caused by Windows default power management strategy for USB hubs, hence my previous recommendation to disable this “feature” - I, too, wondered why things were repeatedly coming & going, when I obviously hadn’t changed anything...

Cheers,
Carl

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turfpit
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Re: Connecting multiple ZWO cameras

Post by turfpit » Sun Nov 04, 2018 9:00 am

Robin, Bill, Carl

I agree with Carl - I have seen this one before and turning off the USB Selective suspend is a sensible step to reduce complexity when debugging these type of USB issues.

See https://www.windowscentral.com/how-prev ... sb-devices. This is for Windows 10 but does apply to Winndow 8.1 and 7.

This has been around since Vista was released https://support.microsoft.com/en-us/hel ... -power-man.

To debug this, I would start off with 2 cameras, 2 cables and the PC/laptop only. I wouldn't fancy 2 USB3 cameras connected to the same hub as a hardware config.

Dave

wcblack7
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Re: Connecting multiple ZWO cameras

Post by wcblack7 » Mon Nov 05, 2018 1:21 am

Hi all,
Wanted to report that I "fixed" the power management options in Windows 10 as you suggested and that solved it!
I now have both cameras available with the SharpCap native controls regardless of how I have them attached to the USB ports.

It also solved a couple of other annoyances I was encountering:
- High number of dropped frames: I noticed that when I fist connected to a camera that I would have no dropped frames for about 20s after that the dropped frame rate would jump up to about 20% (ugh!)
- Sudden changes in image brightness: at certain low light levels I would notice that suddenly I would see a change in overall frame brightness once in a while, with it going brighter and then back darker, intermittently. This would really cause a problem with running a sensor analysis while the program was searching for the right exposure time for a given gain level.

Thanks everyone for taking time and responding!
Bill

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turfpit
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Re: Connecting multiple ZWO cameras

Post by turfpit » Mon Nov 05, 2018 9:53 am

Bill

Good to hear you are working and thanks for reporting back.

Can you download and run USBtreeView https://www.uwe-sieber.de/usbtreeview_e.html and post back an image of the graphical USB representation on the left hand side.

Robin - If this shows a single xHCI controller that will be interesting. We then we need to think how far up the USB debug chain turning off the USB Selective Suspend needs to be? probably comes after all the cable checking items (which is where most of the problems seem to occur)?

Dave

celkins
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Re: Connecting multiple ZWO cameras

Post by celkins » Mon Nov 05, 2018 9:54 pm

Really glad to hear that we’ve got you up & running, Bill

Guys, I would strongly recommend that disabling power saving should be the first step, not even in debugging, but in normal setup - as it doesn’t produce just a single symptom, but a host of undesirable behaviours that are hard to explain...

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turfpit
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Re: Connecting multiple ZWO cameras

Post by turfpit » Mon Nov 05, 2018 11:56 pm

Carl

Could you post the USBtreeView graphic for your machine please.

Dave

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