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 at the very least as soon as all of us needed to take care of it at dwelling or work to connect with a Private Pc port with totally different gadgets, that’s, to attach extra gadgets than the variety of USB ports accessible within the PC.

Nicely, the hub is a multiplier of USB ports that permits, ranging from a channel linked 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 ability provide. The sorting consists of a repetition of the info channel, which is possible as a result of, in keeping with the Common Serial Bus protocol, a USB bus, consisting of the canonical two knowledge wires (D+ and D-) referred to the frequent floor with the ability provide (GND), may be approached 127 gadgets (the 128th is the Host, i.e., the Grasp unit of the bus).

Though available on the market you will discover hubs of all sizes and styles, powered or not, it appeared fascinating to develop our mission and suggest it on these pages, for at the very least 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 linked by micro USB connector on the facet to develop 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 element, which is the Terminus FE1.1 built-in circuit, which internally incorporates an entire USB 2.0 Excessive-Pace hub with 4 ports (known as “downstream”) plus one enter (or begin, in the event you want, 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 akin to GSMA Common Charging Resolution (UCS), which is absolutely compliant with USB-IF specification “Common Serial Bus rev. 2.0 and Battery Charging rev. 1.1; the machine 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 total 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 help Charging Downstream Ports mode, as outlined by the USB-IF specification; by enabling this function, the USB hub may be simply remodeled right into a battery charging resolution for transportable gadgets akin to smartphones and tablets.

This established, we will go analyzing the wiring diagram, by which we will see the built-in U1 linked within the basic 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 ability provide for the chip and the 4 USB gadgets.

The built-in circuit has an inside 3.3V voltage regulator whose output voltage, accessible 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 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 facet operates at 5V.

The operation of the entire, and specifically the info price of the USB ports, is synchronized by the interior 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 simply see within the circuit are used to set or disable some options of their pins: for instance, the one linked on pin XRSTJ units at a excessive degree the exterior reset line, which on this mission 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, you must join a usually open unipolar button between pin 17 and GND and you’ll get it.

R4 units the Bus Energy Sense operation by 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 facet (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 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 operate, which means that the built-in unit screens the presence of energy on the USB bus on the Host facet: a excessive degree implies that the Host is powered. Subsequently the hub can work usually, whereas if the extent is low, it implies 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 interior logic to activate the diodes in multiplex mode. In follow, the management of LEDs is as follows: when you must 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 must 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} machine is linked 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 linked 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 at all times flows within the resistor.

We proceed with the circuit evaluation by going to resistor R6, which units the bias present of the analog levels 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 we have now described performs the identical duties because the USB 2.0 hubs that you will discover available on the market and due to this fact means that you can join as much as 4 USB gadgets (for instance, printers, mice and keyboards, scanners …) in machine mode to a single USB port, which may be that of a private laptop.

It additionally offers energy to the gadgets, supplied that they soak up, 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 depend on the next present to the output ports must interrupt the monitor 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 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 tools, maybe mixed with a Raspberry Pi board.

FROM OPENSTORE

Chip 1 IN – 4 OUT USB 2.0 Excessive Pace