This article explains why a computer may report "Too many USB hubs" if USB port replicators, hubs, or extensions are used between a computer and a Prowise Touchscreen One & TEN Gen 2. This article also describes the number and position of internal hubs in Prowise Touchscreen One & TEN Gen 2.
Questions & Answer
Q: Why does my computer report "Too many USB hubs" or "cannot start (code 10)" when I connect a Prowise Touchscreen One & TEN Gen 2?
A: The USB standard allows connecting USB devices in a maximum of seven tiers.
Of that, only five non-root USB hubs may exist in series. This is because each USB hub is both a device and the start of a new tier.
Adding too many USB port replicators, docking stations, hubs, or extenders or active USB cables between the computer and a Prowise Touchscreen One & TEN Gen 2 can prevent some of the display's functions from working correctly if the seven-tier limit is exceeded.
Prowise Touchscreen One & TEN Gen 2 are compound USB devices (a device containing multiple functions) that contain internal USB hubs, and so they occupy more than one USB Tier. The more advanced or complex a Prowise Touchscreen model is, the more hubs it may use internally.
The USB HUB tiers Setup for the Prowise Touchscreen Ten & One G2
The HUB Tier levels on the mainboard are marked in the Red square in the schematics.
USB signal routing [Android]
USB signal routing [OPS]
USB signal routing [USB-B]
USB signal routing [USB-C]
Note: For normal point to point connections there will be no limitations of USB functionalities as can be seen in the above schematics.
When using external devices with internal HUB Tiers between the point to point connection like a docking station, replicators, or active cables
This can result in USB Tiers not being established to work correctly due to the USB HUB Tier Topology as can seen below.
Between Tier 1 and Tier 7 there can only be a maximum of 5 Tiers. Peripherals should therefore always be in Tier 7 or lower. Otherwise the connected device will not work.
“Peripherals” refers to external USB devices plugged into a USB Type-A port on the display.
Examples: a USB memory stick, keyboard, mouse, webcam, and so on.
In Windows, you can use the Device Manager's View > Devices by Connection option to see which devices are connected to each other. After seeing these connections and locating the USB controller and root hub (usually on a PCI BUS), you will then be able to see how many USB tiers are in use.
Working example:
The setup is as follows:
- Laptop [Tier 1]
- Docking station with 2 USB HUB Tiers [Tier 2,3]
- Passive USB Touch cable
- Prowise Touchscreen One & Ten G2 [Tier 4, 5, 6]
As can be seen below the setup is using 7 tiers in total from laptop to Prowise Endpoint.
Non working example:
The setup is as follows:
- Laptop [Tier 1]
- Docking station with 2 USB HUB Tiers [Tier 2,3]
- Active USB Touch cable [Tier 4]
- Prowise Touchscreen One & Ten G2 [Tier 5,6,7] → all devices connected to Tier 7 are out of reach.
As can be seen below the setup is using 8 tiers in total from laptop to Prowise Endpoint.
Notes:
- The USB Root Hub resides in the first USB tier, and creates Tier-2 for devices to be connected.
- A USB 3.0 HUB may appear functionally as two hubs: one for 'Superspeed" devices and one for slower devices.
- Some computers have multiple internal USB hubs, which occupy additional tiers in the USB topology. This reduces the number of usable tiers between the computer and the Prowise Touchscreens.
- Different Prowise Touchscreen models use a different number of internal USB tiers, depending on the display's internal architecture and functions.
- Some USB extenders will also occupy one or more USB device tiers, but may not report as one or more USB hubs in Windows Device Manager. This is due to increases in signal timing latency, and is not observable in software tools like Windows Device Manager.
- You can use third-party tools, such as USB Device Tree Viewer, to view the USB device connection tree.