Based mostly 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 a minimum of as soon as all of us needed to take care of it at residence or work to connect with a Private Laptop port with totally different gadgets, that’s, to attach extra gadgets than the variety of USB ports obtainable within the PC.
Effectively, 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 info channel, which is possible as a result of, in response to 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), could be approached 127 gadgets (the 128th is the Host, i.e., the Grasp unit of the bus).
Though available on the market you could find hubs of all sizes and shapes, powered or not, it appeared attention-grabbing to develop our mission and suggest it on these pages, for a minimum of 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 broaden the probabilities (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
Your entire hub has been realized by a single part, which is the Terminus FE1.1 built-in circuit, which internally incorporates an entire USB 2.0 Excessive-Pace hub with 4 ports (referred to as “downstream”) plus one enter (or begin, for those who choose, which is the “upstream”), all encapsulated in a 14+14 pin SSOP SMD bundle, as you see in Fig. 1 the place the pinout of the built-in circuit is proven.
Fig. 1
Our part 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 gadget 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 could be utilized on the analogue front-end (AFE). Excessive, Full, and Low Pace throughout construct and testing.
The FE1.1 might be optionally configured to assist Charging Downstream Ports mode, as outlined by the USB-IF specification; by enabling this characteristic, the USB hub could be simply reworked right into a battery charging resolution for moveable gadgets similar to smartphones and tablets.
This established, we are able to go analyzing the wiring diagram, through which we are able to 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 are 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 degree on pin OVCJ, which is the safety stage towards 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 specifically the info fee of the USB ports, is synchronized by means of 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 degree the exterior reset line, which on this mission we don’t use and subsequently 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, you might want to join a usually open unipolar button between pin 17 and GND and you’re going to get it.
R4 units the Bus Energy Sense operation by means of the VBUSJ pin, whose standing identifies the first energy supply of the hub; in our case, the excessive degree 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 by means of the USB Host socket, and subsequently 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 operate, which means that the built-in unit displays the presence of energy on the USB bus on the Host aspect: a excessive degree 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 subsequently 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 are LED1 (pin 23) and LED2 (pin 24); the 4 LEDs have, in flip, a typical 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 you might want to mild LD1 and LD2 (or simply one of many two), you set the DRV line to a excessive degree and LED1 and/or LED2 to zero logic, whereas when you might want to mild LD3 and/or LD4, you ship the DRV to zero logic and put LED1 and/or LED2 to a excessive degree.
The primary output manages the LEDs indicating {that a} gadget is related to the downstream ports 1 and three, i.e., LD1 considerations 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 sequence (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.
Part 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 could find available on the market and subsequently means that you can join as much as 4 USB gadgets (for instance, printers, mice and keyboards, scanners …) in gadget mode to a single USB port, which could be that of a private laptop.
It additionally gives energy to the gadgets, offered 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 a better 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 normal contemplates for USB ports; the factor is completely possible, though it was not completed in our hub as a result of the circuit was not created with that objective.
The circuit can nonetheless be used as a stand-alone hub or built-in into present gear, maybe mixed with a Raspberry Pi board.
FROM OPENSTORE
Chip 1 IN – 4 OUT USB 2.0 Excessive Pace
