USB/VGA 2 port switch - Electronic Circuits Projects Diagrams Free

theforce · 1st March 2007, 09:05 PM

I need some help designing a USB/VGA 2 port switch.

Here is some quick background and what I need it to do.

I installed a motorized Lilliput LCD touch screen in my car now and I need to be able to switch between my Can-View device and a computer.

The Can-View uses the USB from the touch screen as well as outputs video through VGA.

I have tried a 2 port USB/VGA switch but since it emulates keyboard and mouse it screws up the USB signal to the Can-View as well as the screen when a PC is hooked up. So what I need to do is make a switch that disconnects the USB signal completely like a physical disconnect. Of course the VGA will be a physical disconnect also.

So what I need is a way to switch the 2 USB data wires ( +5 and ground dont really need to be switched since they are there just for voltage. Unless someone here says they need switched anyway. ) and the 5 VGA wires RGBVH. A total of 7 switches unless some of the other VGA wires are needed.

Relays would make this a real PITA to work with and also need a lot of power. What I'm hoping for is an easier way to do the switching through some cheap easy to find ICs.

I currently have some AND/OR gates as well as some 4066 analog switches.

I dont know much about what USB data is and how its transmitted so I just need pointed to the right hardware to do the job. I'm limited to only DIP ICs as I do not have the necessary hardware to do any surface mounting ICs.

I think all I will need help with is the parts to do the switching because everything else I can use from my previous project. 555 timer for the debouncer, a decade counter for the selection of the device, and some AND/OR gates if I need them.

hjames · 2nd March 2007, 04:23 AM

Googling around for some background info...

Can-view is an interface for the Toyota hybrid car
http://hybridinterfaces.ca/index.html

And a very similar post over at:
http://www.dutchforce.com/~eforum/in...=0&#entry87302

which I would pretty much repeat. The main issue is that VGA signals are ~20MHz analog lines with an impedance of 75R. Putting a 4066 with a 100R impedance, or a HC4066 with 40R impedance will not work. Look at the chips that Maxim makes, and seriously consider just using one of them. SOIC's are really easy to solder if you are reasonably careful, and a custom PCB with decent analog routing is required.

As for the USB, the 4066's *might* be enough - the touchscreen interface is probably a low speed usb device - 1.5MBit, and a 4066 would probably do a passable job of switching the signal.

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1st March 2007, 09:05 PM	(permalink)
theforce	USB/VGA 2 port switch I need some help designing a USB/VGA 2 port switch. Here is some quick background and what I need it to do. I installed a motorized Lilliput LCD touch screen in my car now and I need to be able to switch between my Can-View device and a computer. The Can-View uses the USB from the touch screen as well as outputs video through VGA. I have tried a 2 port USB/VGA switch but since it emulates keyboard and mouse it screws up the USB signal to the Can-View as well as the screen when a PC is hooked up. So what I need to do is make a switch that disconnects the USB signal completely like a physical disconnect. Of course the VGA will be a physical disconnect also. So what I need is a way to switch the 2 USB data wires ( +5 and ground dont really need to be switched since they are there just for voltage. Unless someone here says they need switched anyway. ) and the 5 VGA wires RGBVH. A total of 7 switches unless some of the other VGA wires are needed. Relays would make this a real PITA to work with and also need a lot of power. What I'm hoping for is an easier way to do the switching through some cheap easy to find ICs. I currently have some AND/OR gates as well as some 4066 analog switches. I dont know much about what USB data is and how its transmitted so I just need pointed to the right hardware to do the job. I'm limited to only DIP ICs as I do not have the necessary hardware to do any surface mounting ICs. I think all I will need help with is the parts to do the switching because everything else I can use from my previous project. 555 timer for the debouncer, a decade counter for the selection of the device, and some AND/OR gates if I need them.

2nd March 2007, 04:23 AM	(permalink)
hjames	Googling around for some background info... Can-view is an interface for the Toyota hybrid car http://hybridinterfaces.ca/index.html And a very similar post over at: http://www.dutchforce.com/~eforum/in...=0&#entry87302 which I would pretty much repeat. The main issue is that VGA signals are ~20MHz analog lines with an impedance of 75R. Putting a 4066 with a 100R impedance, or a HC4066 with 40R impedance will not work. Look at the chips that Maxim makes, and seriously consider just using one of them. SOIC's are really easy to solder if you are reasonably careful, and a custom PCB with decent analog routing is required. As for the USB, the 4066's might be enough - the touchscreen interface is probably a low speed usb device - 1.5MBit, and a 4066 would probably do a passable job of switching the signal.