run ad2 without active usb

[darth458]

I want to setup the ad2 to do a particular thing and then pull the plug on the USB and let it do that thing powered up from the separate supply. How can I do that please?

[attila]

Hi @darth458

The AUX supply is stopped when the USB voltage drops, see IC48 supply is from VBUS:
https://digilent.com/reference/test-and-measurement/analog-discovery-2/hardware-design-guide#usb_power_control

You could use a powered USB hub to supply and configure the device. Set the "On Close" option to Continue the outputs to work after application close or disconnect the computer from the hub.

[darth458]

Hi Attila, thanks for that information. Has that interface been around for awhile? I assume it is part of your GUI software but I didn't know it existed before. 

On another note, do you have the 4 hole locations for the PCB? I am making a metal box and want to mount the unit without the plastic cover. It looks like a square array but it's easy to mis-measure by a half mm. Is it possible for me to know explicitly or by a diagram the physical locations of the holes? As well if I knew even more about the layout it would help me engineer a metal box. If I do that I will upload the design files.

Edited September 16, 2022 by darth458

[attila]

Hi @darth458

The Options are under Settings menu (on Window and Linux) or the gear button in the top-right corner or in the status bar the version info button.

You can find 3D models here:
https://digilent.com/reference/test-and-measurement/analog-discovery-2/start#additional_resources

Edited September 16, 2022 by attila

[darth458]

Hi Attila,

We are not finding that the switchover works. That is, with the system set to continue and hooked up to a 1A wall wart AND the USB the expectation is that the USB cable could be pulled and the diode would switch over to the wall wart. I think you are saying to have a powered USB hub and then when you disconnect that from the computer there would be no need for the wall wart anyway but power would stay exactly the same when the hub uplink to the PC was pulled.

It seems like perhaps there is an unacceptable dropout unless the wall wart has a higher voltage like 5.75V. I thought that setting continue would fix things, not having used that interface before, but it did not.

In spite of the complex explanation of the various modes the bottom line is that it won't switch fast enough to prevent a fatal dropout. You have to use a powered hub anyway.

Do you see a flaw in my argument?

thanks,

Steve

 

[attila]

Hi @darth458

The voltage monitor for the AUX supply is powered from the USB voltage so the AUX is cut when the USB is removed, this is the intended behavior for the device, see:
https://digilent.com/reference/test-and-measurement/analog-discovery-2/hardware-design-guide?#usb_power_control

[darth458]

Hi Attila,

We bought a powered hub. Now we set up waveforms to be generated and get them going and we pull the connection to the PC but since the hub is powered there is never a change in DC power and we do not transition to external mode. We do not have external power hooked up. All that happens is that the signal connectors that carry usb signals are removed. Still it breaks. I can use wireshark to see if there is USB activity between the AD2 and the host I suppose. 

[attila]

Hi @darth458

I've just tested this with a powered USB hub and the (analog and digital) outputs of the AD2 continues after the hub is disconnected from the computer.

Isn't you hub shutting down the supply output when disconnected from the host ? or causes a glitch in the supply which resets the device ? 

[darth458]

Hi Attila, thanks for your continued attention. Apparently this behaviour is hub-dependent. I will ask my colleague on-site to look at the +5V directly on the hub port. The hub we have has a "power port" with the little lightning bolt symbol which is supposed to remain powered but I also read that in a powered hub when you disconnect from the PC the hub may essentially crash. I do not know whether the blue lights on the hub ports are really connected to their individual VCC pins or to some pins on the hub logic board if you know what I mean. I also asked him to cut the +5V line on a usb cable and power the AD2 with the external. If he hooks up the usb with no +5 and then connects external power the AD2 should come up. And when he pulls the plug from the PC there ought to be no glitch.