Devices randomly disconnecting
Last updated · SimHub 9.11.22
If devices drop out at random — a screen that disconnects and reconnects in a loop, an Arduino that dies mid-session, a USB sound card that vanishes the moment a game launches — start with two Windows settings before you suspect the hardware. Turn off "Allow the computer to turn off this device to save power" on every USB Root Hub in Device Manager, and set USB selective suspend to Disabled in the advanced power settings. Between them those cause a large share of these reports. What remains is electrical: interference and bandwidth. Use shielded cables under 1.5 metres, spread devices across separate controllers rather than one hub, and prefer rear motherboard ports to the front panel.
Random disconnects feel like a failing device and usually are not. Windows is allowed to power down USB ports it thinks are idle, and a dashboard screen that only updates at 60 Hz over a serial link can look idle to it.
The two Windows settings, first
Do these before anything else. They are free, reversible, and between them account for a large share of the reports.
Stop Windows powering down the USB hubs
Open Device Manager. Expand Universal Serial Bus controllers. For every entry called USB Root Hub, open Properties → Power Management and clear Allow the computer to turn off this device to save power. There is usually more than one; do all of them, because the one you skip is the one your dash is on.
Disable USB selective suspend
Control Panel → Power Options → Change plan settings → Change advanced power settings → USB settings → USB selective suspend setting → Disabled. This is a separate mechanism from the per-hub setting above and disabling one does not disable the other.
Reboot and retest
Both settings apply properly only after a restart. Race a session before deciding whether it worked — these faults are intermittent by nature and a five-minute test proves nothing.
Why these exist at all. They are laptop battery features. On a desktop driving a rig they save a trivial amount of power and cost you a device mid-race, which is a bad trade in every direction.
Interference and bandwidth
What the settings do not fix is electrical. Two distinct problems hide under the same symptom:
- Interference (EMI)
- A rig is a metal frame full of motors, a direct drive base and long unshielded runs. Use good shielded cables, keep them under about 1.5 metres, and add ferrite cores on the runs that misbehave. Route data cables away from power cables and away from the wheelbase rather than alongside them.
- Bandwidth and endpoint overload
- USB devices share a controller, and a controller has limits on throughput and on endpoints. The wiki attributes USBD480 display problems to bandwidth overload specifically, and notes that USB sound devices can trigger random disconnections of other devices through endpoint overload.
The sound card clue. If other devices drop out at the moment a game launches, and you have a USB sound card — a common ShakeIt setup — move the sound card to its own controller. That is a documented cause, and it looks exactly like a game compatibility problem when it is not one.
Spreading devices across controllers is the practical fix for both. Front-panel ports usually hang off one internal header, so a front panel full of devices is one controller doing everything; rear ports are more often spread across several.
Devices with known histories
| Device | What the documentation attributes it to | What to do |
|---|---|---|
| Vocore screens | USB instability | Update the firmware with the official v2scrctl tool before chasing anything else. |
| Vocore MPRO | Early firmware versions were unstable | Same — firmware first. A screen bought early in a production run is the likely case. |
| USBD480 displays | USB bandwidth overload | Give it a controller with less on it. This is a throughput problem, not a fault. |
| USB sound cards | USB endpoint overload affecting other devices | Separate controller. The symptom appears on the other device, which is why this is hard to spot. |
Common questions
Why does my SimHub screen keep disconnecting and reconnecting?
Most often Windows powering down the USB port. Clear "Allow the computer to turn off this device to save power" on every USB Root Hub in Device Manager, and set USB selective suspend to Disabled in the advanced power plan settings, then reboot. On a Vocore, update the firmware as well — instability there is documented.
My Arduino disconnects mid-race. Is it broken?
Usually not. Work through the two Windows power settings first, then the electrical causes: a shielded cable under 1.5 metres, routed away from the wheelbase, with a ferrite core if it persists. A rig is an electrically noisy place and a long unshielded USB run is the weak point.
Why do devices vanish when I launch a game?
If you have a USB sound card, that is a documented cause — sound devices can overload USB endpoints and take other devices down with them. Move the sound card to a different USB controller, not just a different port on the same hub.
Front ports or rear ports?
Rear. Front-panel ports usually all hang off a single internal header, so filling them puts every device on one controller. Rear ports are more often spread across several controllers, which is what you want.
Do ferrite cores actually help?
On an interference problem, yes — they are named in SimHub's own USB troubleshooting guidance alongside shielded cables and short runs. They do nothing for a bandwidth problem, so if the fault tracks with how many devices are active rather than with what else is running, look at controller loading instead.
How long should a USB cable be?
Under about 1.5 metres for anything on a rig, and shielded. Longer runs pick up more interference from the motors and the direct drive base, and USB has no error recovery that will hide it from you.
Sources
Related guides
SimHub is developed independently by Wotever and is not affiliated with oesimracing. This page was checked against SimHub 9.11.22 on 4 August 2026; where the interface has moved on since, the version stamp tells you how far. More on what SimHub is and what it costs.