Car dash project - trouble with KVM switch

[turbosax2]

Hi, I'm pretty new to Pi's and this sort of stuff, but am computer savvy so please bear with me. I'm setting up two 3B+ Pi's in my race car for a digital dash. One is running the current version of Raspbian Stretch Lite and I'm not sure about the other since a friend set it up, but it's a GUI. (I can check if this is critical information.)

I'm using this screen in the dash:
https://www.dfrobot.com/product-1655.html

The goal is to be able to use a dash-mounted switch to toggle between the two Pi's since they run different data acquisition software on them. I originally got this HDMI switch and it worked well, but then I quickly realized that I needed to switch the USB cable to the Pi as well for the touchscreen capability:
https://www.amazon.com/gp/product/B079J ... UTF8&psc=1

So then I picked up this KVM switch:
https://www.amazon.com/gp/product/B07P7 ... UTF8&psc=1

I picked that one due to the price and especially the size, since all of this is going into a tight space in my center console. When I just have the HDMI connectors hooked up, that KVM switch works well. But when I hook up the USB connectors to the Pi's, no USB device I plug in will pass through the KVM switch to the Pi, and all of the USB ports on the Pi go dead after a short while. Disconnecting the USB connector brings them back to life again, but after the second time going dead they stay dead until rebooted. This happens whether or not I have a mouse, keyboard, or the screen's USB plugged into the KVM.

I read up a little about this and found it might be a power issue since the KVM is USB-powered, so I plugged in a 2A USB power source to the keyboard port on the KVM switch to make sure it had enough juice. This didn't change anything.

So I'm kind of lost at this point. The KVM switch works well on two W10 laptops and the HDMI part works fine, but I just can't get anything to pass through the USB to the Pi and it keeps killing the USB ports temporarily. Any help would be appreciated. Please let me know what further information is necessary to help!

[fruitoftheloom]

Hi, I'm pretty new to Pi's and this sort of stuff, but am computer savvy so please bear with me. I'm setting up two 3B+ Pi's in my race car for a digital dash. One is running the current version of Raspbian Stretch Lite and I'm not sure about the other since a friend set it up, but it's a GUI. (I can check if this is critical information.)

I'm using this screen in the dash:
https://www.dfrobot.com/product-1655.html

The goal is to be able to use a dash-mounted switch to toggle between the two Pi's since they run different data acquisition software on them. I originally got this HDMI switch and it worked well, but then I quickly realized that I needed to switch the USB cable to the Pi as well for the touchscreen capability:
https://www.amazon.com/gp/product/B079J ... UTF8&psc=1

So then I picked up this KVM switch:
https://www.amazon.com/gp/product/B07P7 ... UTF8&psc=1

I picked that one due to the price and especially the size, since all of this is going into a tight space in my center console. When I just have the HDMI connectors hooked up, that KVM switch works well. But when I hook up the USB connectors to the Pi's, no USB device I plug in will pass through the KVM switch to the Pi, and all of the USB ports on the Pi go dead after a short while. Disconnecting the USB connector brings them back to life again, but after the second time going dead they stay dead until rebooted. This happens whether or not I have a mouse, keyboard, or the screen's USB plugged into the KVM.

I read up a little about this and found it might be a power issue since the KVM is USB-powered, so I plugged in a 2A USB power source to the keyboard port on the KVM switch to make sure it had enough juice. This didn't change anything.

So I'm kind of lost at this point. The KVM switch works well on two W10 laptops and the HDMI part works fine, but I just can't get anything to pass through the USB to the Pi and it keeps killing the USB ports temporarily. Any help would be appreciated. Please let me know what further information is necessary to help!

What Power Supply are you using for your Raspberry Pis ??? The official one is 5.1V 2.5A

https://www.raspberrypi.org/products/ra ... er-supply/

[turbosax2]

I'm bench-testing everything at the moment, but I'm using two Mausberry 3A car supplies (one per Pi) powered by a PC power supply. These will be powered directly by the 12V in the car once put in.
https://mausberry-circuits.myshopify.co ... y-switch-1

[PhatFil]

can you confirm the kvm operates as expected with other h/w is it perhaps a faulty unit?

If it is an ok unit that works with alternative h/w ok, try cutting the +5v feeds from the 2 pi(e)'s usb, and supply the kvm with 5v direct from a stepped down source..(will involve pulling the pcb and finding a suitable point to add the +5v and gnd power supply)

[turbosax2]

The KVM operates as expected with a mouse, keyboard, and the touchscreen when connected to two laptops. But it has not worked as expected for any hardware when connected to the Pi's. So the KVM seems functional.

Thanks for the idea. I think I could accomplish that with hacking up some USB cables rather than pulling the KVM PCB.

[turbosax2]

I tried splitting out the power from the hardware straight to a power supply and got somewhat mixed results. It did work with a USB thumb drive, bu then again I also learned that the thumb drive worked when directly plugged into the KVM switch (presumably due to the lower power demands). At one point I also did get a keyboard to work when wired this way. But when I tried the USB for my touch screen, it did not pass through the KVM at all. And then it finally got to a point where no USB devices pass through the KVM at all, even to two laptops, so I think the KVM developed a fault. I'm hesitant to get another of the same KVM if that is the quality I can expect, so I'm open to suggestions for other options. Thanks for the help so far.