UUGear MEGA4 Bedienungsanleitung
Copyright © 2021 Dun Cat B.V. All rights reserved.
UUGear is a trade name of Dun Cat B.V.
MEGA4: 4-Port USB 3.1 PPPS Hub
for Raspberry Pi 4B
User Manual (revision 1.00)
Copyright © 2021 Dun Cat B.V. All rights reserved.
UUGear is a trade name of Dun Cat B.V.
Table of Content
Product Overview............................................................................................... 1
Package Content................................................................................................ 3
Specifications..................................................................................................... 4
No Back-Power.................................................................................................. 5
About PPPS (Per-Port Power Switching)............................................................ 6
Remotely Reset a USB Device.................................................................... 6
Save Energy ............................................................................................... 6
About Output Current......................................................................................... 7
About MTT and STT........................................................................................... 7
Mount MEGA4 under Raspberry Pi 4B............................................................... 8
Connect Power Supply....................................................................................... 9
Voltages Header and Reset Header................................................................. 10
Software Installation and Usage........................................................................11
Interactive BASH Script..............................................................................11
UUGear Web Interface (UWI).................................................................... 12
Daisy-Chaining MEGA4 Devices...................................................................... 14
Direct Daisy-Chaining ............................................................................... 14
Chaining via USB 3 Extension Cable ........................................................ 14
Stacking Multiple MEGA4 Devices............................................................ 15
Revision History............................................................................................... 18
1
Product Overview
MEGA4 is a 4-Port USB 3.1 PPPS (Per-Port Power Switching) hub designed for
Raspberry Pi 4B. It adds 4 more USB 3.1 ports to Raspberry Pi 4B, and the power on
each port can be turned ON or OFF separately via software.
MEGA4 has the same board size as Raspberry Pi 4B, and can be mounted
underneath. The U-shaped adapter (included) can make data and power connection
between MEGA4 and Raspberry Pi.
MEGA4 is also a powered hub and you can connect 5V power supply to its USB type
C connector and significantly increase its current output ability.
You can turn on/off the power on each USB port via the software or via UUGear Web
Interface (UWI) on PC, Tablet or Smartphone.
Although MEGA4 is designed for Raspberry Pi 4B, you can use it as a USB 3.1 hub
on other computers. You may want to use a USB3.1 extension cable for the
connection.
2
The picture below shows how the board look like:
1~4) Downstream USB port with white LED as power indicator and blue LED as
activity indicator
5) Upstream USB port
6) USB type C power in (DC 5V)
7) Voltages header
8) Reset header
9) Red LED as power indicator for the whole board
3
Package Content
Each package of MEGA4 contains:
MEGA4 board x 1
U-shaped adapter x 1
M2.5 x 10+6mm Copper Standoff x 4
M2.5 screws x 4
M2.5 nuts x 4
4
Specifications
Dimension:
85mmx 56mm x 9mm (USB plug is 7mm protrude)
Weight
29g (net weight without any accessory)
USB Hub Controller
VL817 Q7 (firmware rev 90.23)
Per-Port Power Switch
AP2511 (datasheet)
Ideal Diode MOSFET
AO4447 (datasheet)
Standards
USB 3.1 Gen1 (USB 3.0), 2.0 and 1.1 compatibility
Multiple Transaction Translator (MTT)
Per-Port Power Switching (PPPS)
Per-Port Over Current Protection
Data Speed
USB v3.1 Gen 1: up to 5 Gbps
USB v2.0: up to 480 Mbps
USB v1.1: up to 12 Mbps
USB Ports
Upstream: 1 (A-type USB 3.0 plug)
Downstream: 4 (A-type USB 3.0 female connector)
Output Current
Bus powered only: up to 1.2A in total (limited by
Raspberry Pi 4B)
With supplemental power supply: up to 5A in total, and
2.5A per port (also depends on the power supply)
Static Current
64mA
Operating Temperature
0℃~70℃
Humidity
0~80% RH, no condensing
5
No Back-Power
Back-power (or back feeding power) here means the USB hub provides electronic
power to Raspberry Pi. Because Raspberry PI 4B does not like back feeding power,
MEGA4 does not support back-power either.
On MEGA4 board, there is an "ideal diode" implemented with MOSFET (AO4447).
This "ideal diode" connects the Vbus on Raspberry Pi 4B's USB 3.1 port and the 5V
trace on MEGA4. Hence MEGA4 can draw current from Raspberry Pi 4B and get
powered.
MEGA4 has a USB type C connector, which allows you to connect a supplemental 5V
power supply to increase MEGA4's current output ability. Because of the existence of
"ideal diode", the power provided via USB type C connector will not be fed to
Raspberry Pi 4B.
6
About PPPS (Per-Port Power Switching)
The concept was firstly introduced in USB 2.0 specification, that a USB hub can
advertise three different kinds of power switching on its USB ports:
no power switching
ganged power switching (turn on/off all ports together)
per-port power switching (turn on/off port individually)
The last one is what PPPS stands for. This information can be found if you run
command "sudo lsusb -v".
Although PPPS is included in USB standard for very long time, it is rather difficult to
find a USB hub in the market that actually supports PPPS.
MEGA4 supports PPPS (Per-Port Power Switching).
Not everyone needs PPPS, but it is very useful in some specific cases:
Remotely Reset a USB Device
Some USB devices have their quirks and they might not work correctly after a long
run. After a lot of efforts on troubleshooting, people may find the most simple way to
make the device work again is to reset it (unplug and plug it back). Unfortunately this
cannot be done when the device is in a remote site, and it is a typical scenario that
PPPS can help.
If you have a USB hub that supports PPPS (let's say MEGA4), and that hub is
connected to a computer that has network access (let's say Raspberry Pi 4B), then
you can turn on/off every port on the hub remotely. If you turn off a port and later turn it
on again, the USB device connected to that port will get a full power cycle and hence
will get reset.
Save Energy
Some USB devices are power hungry. You may not want to turn on all USB devices all
the time, especially when your system is powered by battery. If the device is
connected to a USB hub that supports PPPS, you can turn it off when you don't need
it, and that will save energy.
7
About Output Current
If you do not connect a dedicated power supply to MEGA4's USB type C connector, it
will get powered from Raspberry Pi 4B's USB bus. In such case it can draw current up
to 1.2A and its total output current will not exceed that limit.
If you want to connect some high-current devices to MEGA4, you should connect a 5V
power supply to its USB type C connector. In such case the total output current mainly
depends on your power supply, however please keep in mind the USB type C
connector is rated as 5A.Also there is a per-port current limit 2.5A, which comes from
the per-port power switch (AP2511).
About MTT and STT
A USB hub may have two possible ways for organizing Transaction Translators (TTs).
I could have one TT for all downstream ports that have USB devices attached (which
is called Single Transaction Translator, STT), or it could have one TT for each
downstream port (which is called Multiple Transaction Translator, MTT) .
With Single Transaction Translator (STT), connecting one USB 1.1 device to the hub
will force all ports to process data with USB 1.1 standard, thus slowing down all USB
devices on the same USB hub. While with Multiple Transaction Translator (MTT),
each downstream port has its own transaction translator to provide the best USB
performance no matter what class of USB device is connected.
So MTT is better than STT, if the higher price is acceptable.
MEGA4 has Multiple Transaction Translator (MTT).
8
Mount MEGA4 under Raspberry Pi 4B
The recommended way to use MEGA4 is to mount it under your Raspberry Pi 4B. The
first step is to put the 4 copper standoffs on the board and secure them with the
copper screws.
Then you can put your Raspberry Pi 4B on top, and secure it with the copper nuts.
The last step is to plug in the U-shaped adapter and finish the connection.
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