Primarily based on a single chip from Terminus, it means that you can join 4 USB gadgets ranging from a micro USB port; the form-factor is designed for pairing with Raspberry Pi Zero.
Everyone knows what a USB hub is, since not less than as soon as all of us needed to take care of it at house or work to connect with a Private Pc port with completely different gadgets, that’s, to attach extra gadgets than the variety of USB ports obtainable within the PC.
Properly, the hub is a multiplier of USB ports that permits, ranging from a channel related to a USB host (such because the USB connection inside the pc, for instance …) to double, quadruple, and so forth, distributing, along with the bus, even the facility provide. The sorting consists of a repetition of the information channel, which is possible as a result of, based on the Common Serial Bus protocol, a USB bus, consisting of the canonical two knowledge wires (D+ and D-) referred to the widespread floor with the facility provide (GND), may be approached 127 gadgets (the 128th is the Host, i.e., the Grasp unit of the bus).
Though in the marketplace you’ll find hubs of all styles and sizes, powered or not, it appeared attention-grabbing to develop our undertaking and suggest it on these pages, for not less than two causes: it’s a small board simply built-in into different digital gadgets, and furthermore, its form-factor was designed to overlap with the well-known Raspberry Pi Zero, which is related by micro USB connector on the aspect to develop the chances (the Raspberry Pi Zero has just one USB).
So, let’s analyze the wiring diagram of our small common hub, which helps the two.0 Excessive-Pace model of the protocol and means that you can join gadgets enabling communication between them at a pace (data-rate) of 480 Mbit / s.
The USB hub circuit
All the hub has been realized by a single element, which is the Terminus FE1.1 built-in circuit, which internally incorporates a whole USB 2.0 Excessive-Pace hub with 4 ports (referred to as “downstream”) plus one enter (or begin, in case you choose, which is the “upstream”), all encapsulated in a 14+14 pin SSOP SMD package deal, as you see in Fig. 1 the place the pinout of the built-in circuit is proven.
Fig. 1
Our element helps particular options similar to GSMA Common Charging Answer (UCS), which is absolutely compliant with USB-IF specification “Common Serial Bus rev. 2.0 and Battery Charging rev. 1.1; the system means that you can implement a 4-port low-power USB 2.0 hub.
The top quality of the FE1.1 is ensured by the built-in general system scan and self-test mode options, which may be utilized on the analogue front-end (AFE). Excessive, Full, and Low Pace throughout construct and testing.
The FE1.1 could possibly be optionally configured to assist Charging Downstream Ports mode, as outlined by the USB-IF specification; by enabling this function, the USB hub may be simply reworked right into a battery charging resolution for moveable gadgets similar to smartphones and tablets.
This established, we will go analyzing the wiring diagram, by which we will see the built-in U1 related within the traditional configuration that gives a USB connector to connect with the Host (USB H) and 4 peripheral gadgets (USB1, USB2, USB3, USB4) which might be equal to one another, from the USBH can be taken the facility provide for the chip and the 4 USB gadgets.
The built-in circuit has an inner 3.3V voltage regulator whose output voltage, obtainable between pin 21 and the bottom, is filtered by capacitors C1 and C6 and goes to excessive logic stage on pin OVCJ, which is the safety stage in opposition to the extreme present draw. All of the logic contained in the built-in circuit operates at 3.3V whereas the USB knowledge aspect operates at 5V.
The operation of the entire, and particularly the information charge of the USB ports, is synchronized via the inner oscillator that belongs to the quartz Q1; within the wiring diagram, you see solely the quartz as a result of the “load” capacitors that with it contribute to figuring out the oscillation frequency, are built-in into the FE1.1.
The pull-up resistors that you just see within the circuit are used to set or disable some options of their pins: for instance, the one related on pin XRSTJ units at a excessive stage the exterior reset line, which on this undertaking we don’t use and due to this fact we maintain it at one logic (3.3V); the road means that you can reset, for instance with a button, the operation of the hub, if it will get caught, so if you wish to have a tough reset, it’s essential to join a usually open unipolar button between pin 17 and GND and you’ll get it.
R4 units the Bus Energy Sense operation via the VBUSJ pin, whose standing identifies the first energy supply of the hub; in our case, the excessive stage signifies that the hub is self-powered and that the supply has sufficient energy to provide Excessive-Energy gadgets on the downstream ports aspect (that is the case of utilizing an influence provide that gives present -through a coaxial plug- to Vdd5 and GND pins).
In any other case, i.e., if pin 19 is held low, it’s assumed that energy is coming via the USB Host socket, and due to this fact the IC limits the present of every USB downstream port to 100 mA.
R5, utilized to pin 18, manages the Upstream Port Energy (VBUS) Monitor perform, that means that the built-in unit displays the presence of energy on the USB bus on the Host aspect: a excessive stage signifies that the Host is powered. Subsequently the hub can work usually, whereas if the extent is low, it signifies that on the USBH enter socket, there isn’t a energy, and due to this fact the hub is put in a power-down state.
Within the circuit, there are additionally 4 LEDs mounted two by two antiparallelly and pushed by two particular pins which might be LED1 (pin 23) and LED2 (pin 24); the 4 LEDs have, in flip, a standard pin that’s DRV, which is switched by the inner logic to activate the diodes in multiplex mode. In apply, the management of LEDs is as follows: when it’s essential to gentle LD1 and LD2 (or simply one of many two), you set the DRV line to a excessive stage and LED1 and/or LED2 to zero logic, whereas when it’s essential to gentle LD3 and/or LD4, you ship the DRV to zero logic and put LED1 and/or LED2 to a excessive stage.
The primary output manages the LEDs indicating {that a} system is related to the downstream ports 1 and three, i.e., LD1 issues exercise on the USB1 connector and LD3 that on the USB3 connector; when at LD2, it reveals the presence of gadgets related to USB2 (LD2) and to USB4 (LD4).
Every pair of LEDs absorbs a present restricted by the resistor that’s in collection (R1 for D1/D3 and R2 for D2/D4), and that clearly intervenes on just one diode at a time, since, being the LEDs in antiparallel, when one leads the opposite is blocked and vice versa, the present of 1 diode at a time all the time flows within the resistor.
We proceed with the circuit evaluation by going to resistor R6, which units the bias present of the analog phases contained in the IC.
We conclude the outline of the circuit diagram with capacitors C2 and C5, positioned between pin VD18 and floor, which, like these utilized to pins VDD3 (between them and floor), are used to filter the voltage generated by the regulator at 1.8V contained in the built-in circuit.
Element Record:
R1, R2: 470 ohms (0805)
R3, R4, R5: 100kohm (0805)
R6: 2.7 kohm 1% (0805)
C1, C2, C3: 10µF6.3V Ceramic (0805)
C4, C5, C6, C7: 100 nF ceramic (0805)
LD1, LD2, LD3, LD4: Inexperienced LED(0805)
Q1: Quartz 12Mhz (3.2 x 2.5mm)
U1: FE1.1s
USB1, USB2, USB3, USB4: USB-A feminine connector from CS
USBH: Micro-USB connector
Numerous
– Printed circuit board S1459 (86×37 mm)
Scheme
CONCLUSIONS
The small USB hub that now we have described performs the identical duties because the USB 2.0 hubs that you’ll find in the marketplace and due to this fact means that you can join as much as 4 USB gadgets (for instance, printers, mice and keyboards, scanners …) in system mode to a single USB port, which may be that of a private pc.
It additionally gives energy to the gadgets, supplied that they take in, all collectively, the utmost present drawable from the USB of the pc and bearable by the micro USB socket that’s the enter port.
To rely on the next present to the output ports must interrupt the observe that carries the +5V from the micro USB socket to the 4 USB-A and energy the +5V line of the latter with an exterior energy provide, able to delivering all the present that the Common Serial Bus 2.0 commonplace contemplates for USB ports; the factor is completely possible, though it was not carried out in our hub as a result of the circuit was not created with that function.
The circuit can nonetheless be used as a stand-alone hub or built-in into current gear, maybe mixed with a Raspberry Pi board.
FROM OPENSTORE
Chip 1 IN – 4 OUT USB 2.0 High Speed
