6 replies to this topic

[unbreakable goose]

Hi All,


Tonight I noticed that my guide camera and my imagining camera have trouble connecting to my laptop at the same time.

Whenever both are connected, either one or both will drop frames or the camera loses connection altogether.

When I only have one plugged in, everything works without a single problem.

I suspect it's some king of bandwidth problem, but I have no idea how to get around it.

Both my cameras are connected directly to my laptop, my main camera through USB-3, and my guide camera via a USB-3 to USB-C converter, due to limited USB ports on my laptop.

Guide camera: ZWO ASI120mm

Main camera: ZWO ASI183mm pro cooled.

Thanks for the help!

[SgrB2]

I use a 7-port usb 3.0 hub plugged into my single 3.0 usb port on my computer.

The hub has it's own power supply.  Below is the powered hub I use:

 

https://www.amazon.c...B079GT1ZVS?th=1

 

I also use SharpCap and run two ZWO cameras off the hub.  One for

imaging and one for guiding with no problems.

[Tapio]

USB3 can be a problem, especially when you have longer connection.

In fact most of the time the benefits from USB3 in AP are not much.

With guiding you certtainly don't need USB3 and you only lose minimal time in downloads compared to USB2.

The only time I use USB3 is when I do planetary or solar imaging.

[DirtyRod]

I use multiple cameras with SC and PHD2 all the time and actually have my guide camera plugged into my imaging camera. I'd try just plugging the guide camera into the imaging camera and eliminate the adapter to start. 

 

Critical that you use good cables so I would start by just swapping cables. Also, I've found that when I use Shapcap to focus both cameras sometimes Sharpcap seems to try and hang on to my guide camera so after focusing both cameras I generally restart Sharpcap. 

 

Using a hub is a good idea just make sure its powered as suggested above and keep the lengths on the shorter side. I've never gotten consistent connectivity with cables over 2M. 

 

Lastly, make sure that PHD2 is not trying to connect to your imaging camera. When you first set up PHD2 often the wizard will try to connect to the wrong camera giving you disconnects or a blank screen. 

[unbreakable goose]

I use a 7-port usb 3.0 hub plugged into my single 3.0 usb port on my computer.
The hub has it's own power supply. Below is the powered hub I use:

https://www.amazon.c...B079GT1ZVS?th=1

I also use SharpCap and run two ZWO cameras off the hub. One for
imaging and one for guiding with no problems.

All the rest of my setup up is connected via a powered USB hub (mount, hard drive etc), but when I first started noticed these issues, I blamed them on the the fact that everyone was coming through the one usb.


Given that you have done it on a hub, in starting to think my problem is unrelated to how my camera is connected

[unbreakable goose]

I use multiple cameras with SC and PHD2 all the time and actually have my guide camera plugged into my imaging camera. I'd try just plugging the guide camera into the imaging camera and eliminate the adapter to start.

Critical that you use good cables so I would start by just swapping cables. Also, I've found that when I use Shapcap to focus both cameras sometimes Sharpcap seems to try and hang on to my guide camera so after focusing both cameras I generally restart Sharpcap.

Using a hub is a good idea just make sure its powered as suggested above and keep the lengths on the shorter side. I've never gotten consistent connectivity with cables over 2M.

Lastly, make sure that PHD2 is not trying to connect to your imaging camera. When you first set up PHD2 often the wizard will try to connect to the wrong camera giving you disconnects or a blank screen.

Interesting! I didn't consider connecting the cameras together, I'll give that a go tonight.


I have a powered USB hub to control the rest of my setup (mount, hard drives etc), but at first I blamed the issues on the hub and the fact that both my cameras were running though the same port. But I'm thinking I was wrong with that, given everyone here has ran through a hub with no problem.


I think you are right on the money with PHD2 connecting to the wrong camera! I'll double check, but it would explain everything

[CrossAerialPhotography]

Hi All,


Tonight I noticed that my guide camera and my imagining camera have trouble connecting to my laptop at the same time.

Whenever both are connected, either one or both will drop frames or the camera loses connection altogether.

When I only have one plugged in, everything works without a single problem.

I suspect it's some king of bandwidth problem, but I have no idea how to get around it.

Both my cameras are connected directly to my laptop, my main camera through USB-3, and my guide camera via a USB-3 to USB-C converter, due to limited USB ports on my laptop.

Guide camera: ZWO ASI120mm

Main camera: ZWO ASI183mm pro cooled.

Thanks for the help!

I actually think the answer is none of what has been mentioned so far.

 

You mentioned your laptop has USB 3, and USB-C. Unfortunately, better naming conventions matter. I am on going to convert these to their full USB naming conventions for simplicity. USB 3.0 Gen 1 is a 5Gbps connection, typically. That is USB called USB 3.2 Gen 1 in modern terms ( and because USB has the worst naming setup ever) Typically, USB-C is a 10Gbps port but can be 5 Gbps. What is your port?

 

These ports matter because the bandwidth matter. Inside of most laptops, there can be either 1 or 2 USB controllers than controls all the USB IO (yes, there is essentially a hub in your computer). The hubs can control many devices, and have hubs connected to them. There is a limit, but it is really really high

 

I'll get back to these ports in a minute. 

 

 

Device wise, you mentioned several devices and two cameras: ZWO 120MM and 183MM. The 120MM is a USB 2.0 device maxing out at 410 Mbps. You will not saturate a USB 3.0 5 Gbps or 10Gbps port with that data rate (USB-A vs USB-C does not matter, yet)

 

The 183MM is a different beast. With it's USB 3.0 Gen 1 output, and very high MP count, it can easily max out not only a Gen 1 3.0 port, but a CPU, RAM, HDD, and even a slower SATA SSD.

 

 

To explain more simply, your Laptop has a 5in diameter hose into it.

 

If we are only pouring a little water in, no worries the hose is fine. But since water is incompressible, once that hose is maxed, it's maxed. The same is true for the USB port, once it is maxed, other data isn't getting in. Now this is oversimplified because these devices are not constantly outputting data. However...

 

You also mentioned using Sharpcap. That means these camera's are not capturing 1 frame every 2-3 seconds like guiding with the 120MM, or 1 Frame ever 3-5 minutes with the 183MM and deep sky imaging, but instead, I would venture to guess you are imaging at the either 2-3 FPS on the 183, if at full Bin 1 resolution. That will saturate the USB port. You could limit this by lowering the USB speed to 50-60% so that is has some more room for other devices, or making sure that if your laptop had 3-4 USB ports, seeing if some of them are not connected to same controllers. You also mentioned hard drives. In terms of the controllers bandwidth, if it is maxed writing data from the camera, it is maxed from transferring to the drive as well. Storing it internally, then transferring later would work better (assuming these are all on 1 USB controller and you are hardware limited)

 

I also cannot tell from your post, but if you have the camera's connected to another program, then also connecting via sharpcap, that will not work. The ASCOM protocols getting goofy with multiple connections and the cameras cant be used simultaneously by different programs. 

 

 

 

*About USB ports, USB 3.0, USB-C, and hubs

 

Theoretically, USB is backwards compatible. USB 3.2 Gen2x2 (yes that is real) should be able to support a USB 2.0 device. In practice, it is not always true. USB hubs are notorious for having bad USB controllers and heck, even some laptops have bad controllers. USB-C is even worse because it has so many pins that sometimes, a manufacturer decides to not use a pin that is redundant, but that makes it not connect to another device that also did the same thing, just choosing the opposite pin. Adapting USB 3.0 to USB-C is asking for trouble. It can work, but as someone who has literally tested hundreds of USB-C cables I can assure you that they are rare. 

 

Typically, USB 2.0 is pretty reliable and works well with USB 3.0 Gen 1 and 2 fine. USB 3.0 Gen 1 can be finicky because it is the lowest bar so many manufactures have parts and cables that just barely work to reach the speed. USB 3.0 Gen 2 is actually a little better because it is more expensive and harder to achieve, coupled with better rules for certification, so manufactures actually have to put in some effort. They either work or they don't, which I feel is almost better. USB-C with native USB-C devices are typically reliable, but hubs on USB-C are not. 

 

They typically are USB-3.0 Type A hubs with a Type C cable slapped on the end. Due to pin out differences, this can lead to issues.