Re: First Light with CMOS camera - M8
USB-2 hub technology is a bidirectional “two way alternate” technology, whereas USB-3 is “differential, two way simultaneous” transmission. This idea goes back to the days of using copper wire serial port cabling and synchronous transmission (current loop) used in early days of computing, predating PC’s. Synchronous serial ports back then improved speed using a separate line for sending & receiving.
If you want better performance when sharing USB accessories, especially (the now out-dated) USB-2, with USB-3, you would be very wise to use a USB-3 hub going to a USB-3 port on the PC. A typical USB-3 hub splits USB-2 traffic from the USB-3 traffic, so there are effectively two highways, and the USB-3 is even a double lane road. USB-3 hubs have separate comms chips to accommodate each technology, so all the USB-2 traffic has to wait in line for to their send or receive, for each such device and also whether sending or waiting for a response. Meanwhile USB-3 accessories (inside the same hub), use the fast lane and don’t wait for, or collide with traffic coming in or going out between the USB-3 accessories sharing the USB-3 hub and the host USB-3 PC port. The USB-3 hub really acts & performs as two independent hubs.
So, if you MUST share USB-2 and USB-3 accessories, using just ONE hub, make it a USB-3 hub, perhaps a 7-port device, and attach it ONLY to a USB-3 port. Otherwise the USB-3 hub just falls back into the slow USB-2 mode for everything shared to it. Then your only option is two USB-2 hubs or attaching directly to a separate USB, PC port.
You can Google the USB technology consortium, for more info on the differences - Your best performance with much reduced traffic conflict, is a USB-3 hub (for mixed USB type devices), plugged into a USB-3 PC port.
From: Robert Chozick rchozick@... [ap-gto]
Sent: Sunday, August 4, 2019 12:53 AM
Subject: Re: [ap-gto] First Light with CMOS camera - M8
Thank Steve and Mike. I think my setup is ok. I use a Mac with Nebulosity. My cables are not over 3 meters. I just ordered some of the cables Dale recommended. I have a new USB 3 hub since I took the images.
The comment about bandwidth being used was interesting. I do run my Lodestar guider with the camera into the same hub. I hope that doesn’t count as too much bandwidth because that has to happen. My hub has the 1) ZWO camera, 2) GPUSB for the AP 900 CP3, 3) Micro Touch focuser, 4) Lodestar guider and 5) USB- serial interface for the mount to run The Sky. The camera is the only USB 3 item.
I did use the USB hub on the camera for the guider for the images that messed up. I am now setting it up to have the guider have a separate cable so as not to have a hub connect to a hub.
The camera did malfunction both nights after 3-4 hours of use. My later subs were unusable.
I am going to set it up at home when the clouds clear, maybe the end of next week. I want to finish my tests in time to be able to return the camera or have it replaced within the 30 days.
You are correct that there is no better customer support for any product on this earth as what AP provides. It is an oasis.
I hope this camera pans out as I can’t believe how good the subs are for so short a time.
On Aug 3, 2019, at 5:31 PM, sreilly24590@... [ap-gto] <ap-gto@...> wrote:
No matter how good the product it becomes limited by its lack of support. Too bad more manufactures don’t see this. That’s one issue you won’t have with AP products. It doesn’t get better than this.
Just getting in late on the conversation but how long a run are you going with the USB cable? If you’re over 16’ you really need and want an active extender cable and if you are using a hub make sure it’s a powered hub. Using a laptop vs a desktop computer? All drivers up to date? Software as well? Just a few things to look at to make sure you’re as up to date as possible.
From: ap-gto@... <ap-gto@...>
Thanks Dale. I am having some trouble with darks and I have been using that cable that came with it. I will reshoot the darks. I am also having trouble with the camera sometimes sending out bad data and this is with a better cable. It happened on 2 nights after being used for a few hours. I have some subs that are unusable. ZWO is ignoring me on support. I may return the camera just for that reason but I really like it.
On Aug 3, 2019, at 6:10 AM, Dale Ghent daleg@... [ap-gto] <ap-gto@...> wrote: