USB/VGA 2 port digital switch needed

**theforce** · 01-27-2007, 04:32 PM

I'm just getting my in car computer started and I'm looking for a way to switch between my Can-View and a computer. I've done a lot of research on here and google but I cant seem to find what i'm looking for.

The Can-View is a device that is made for the Toyota Prius that allows you to view every thing that the car is doing. The V4 of the Can-View requires an external Lilliput screen to function. I bought the Lilliput GL701-NPCT from computergeeks.com. Based on the information here I thought this was going to be a bad thing but it turned out that I got the newer version of the product and so far it has worked perfectly. I'm very happy with it. The only problem with it is that it is very hard to see the screen during the day. After about 15-30 min of use the screen brightens up a bit making it a little more viewable.

Any way what I'm wanting to do is to switch between my Can-View and a computer. All I need is a switch that has a 2 port USB/VGA and must have a digital push button to switch between the 2 devices. I have found USB/VGA switchers but they all like to combine the USB keyboard and USB mouse inputs. I bought a switch like this just to try and it wont switch between the 2 devices and the Can-View will not respond to any touches. The USB/VGA switch is some how messing up the USB data or somthing.

If there is no switch out there that can do this my only other options are to make a digital switch with a bunch a relays or get something like an 8 pole manual rotary switch. I really want to stick with the digital switch options so I can route a small push button switch to my dash. I dont really have room on my dash for the manual rotary switch and all the wires.

Does anyone here know of a switch that can do what I need it to do? or am I stuck building one?

**Jahntassa** · 01-27-2007, 04:45 PM

The only 'switches' that i've seen that have that capability are KVM's, which as you've said you've already tried. You can try different brands, though, and see if any work better than any others.

Unless someone else knows of something, you're probably going to have to deal with a switch.

One of the things with the USB KVMs is that they 'emulate' themselves, so the computers don't think they're ever disconnected even if you're on another input. That functionality is probably what caused you problems.

**2k1Toaster** · 01-27-2007, 04:54 PM

Well what you want is basically to switch between 2 views on a single monitor. And then when a certain monitor is active, you want a certain usb feed to the computer and not the other right?

**theforce** · 01-27-2007, 05:10 PM

Thats what I want. When I'm on the Can-View I dont want my PC to be accepting the touch screen input. The same goes for when I have the PC selected I dont want the Can-View to accept any touches from the screen. Is just like a regular KVM but like Jahntassa said regular KVMs will want to emulate the keyboard and mouse. I basically need a switch that will just do the switching and nothing else. Something like a bunch of relays would do only in a small form, low power, and something I wont have to build.

**2k1Toaster** · 01-27-2007, 05:28 PM

Well I was thinking along the way of a relay but a transistor. Basically an all electrical relay with 3 leads. If the device is powered through the usb line, then you might be able to get away with only 1 transistor switching between the power line. Basically have the transistor only apply power to the USB device you want. Then a latching gate for the button so that when you push the button option 1 is selected. And option 1 will be selected until you push the button again, and then option 2 is selected and will remain selected until another push. Without that you will have to hold the button down all the time for option 1. And when the button is not pushed down, then option 2.

Really simple.

I reccommend using 4 transisters, one for power, data+, data-, and ground. That way there is a complete disconnect from one to the other.

It would be only 12 solder points. An inexperienced person could do it. Get a USB extension cable (the one with 2 female connectors) and cut it so you get the ports with some wires. Then solder them to the transistors. Each transistor should be paired meaning one transistor 1 have USB1 power, USB2 power, and the selector. Transistor 2 has USB1 data+, USB2 data+, and a selector and so on.

Then test it out with a regualr push button first so that the select is engaged when down or something and see if it switches them.

It will be like physically unplugging the device everytime you switch it off, and then physically replugging when switching back. So there will be that 2 second delay as windows reinitializes the neccessary driver.

**2k1Toaster** · 01-27-2007, 05:30 PM

Oh and a member here is building custom circuits around here for fairly cheap. If you are unsure about your soldering skills or simply don't want to mess with testing, I am sure he will do it for you.

Link: Need a circuit built or designed? I'm your man!

**theforce** · 01-27-2007, 06:33 PM

Thanks I might give him my problem if I cant find a solution.

I have no problems with building circuits myself. The only problem I have is designing them. I did take electronics in HS but it was very limited. Oohms law, resistors, LEDs, AND/OR gates and that was pretty much it.

I did build a video swith for my front and rear camera with the help from an electronics forum. I used a voltage regulator, caps, resistors, transistors, diods, 555 timer, decade counter, OR gate, and some relays. I learned a lot from that project and the people in that forum was very helpfull.

**2k1Toaster** · 01-27-2007, 06:36 PM

well if you did that then is is simple. The switch part has no "logic" involved really.

The latch is just a simple IC you can buy over the counter that works off a pulse and latches.