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​Talk about USB Type-C interface

2021-5-24 15:41:16

 The Type-C I’m going to talk about today is actually one of the USB interfaces. What we see most often is the USB type A interface. What kind of mouse, keyboard, USB flash drive, etc. are all Type A, although there are some beginning  The field has switched to Port C, but its market share is not so fast that it can be popularized for the time being. After all, the current comprehensive manufacturing cost of production is still the current promotion and application manufacturers and consumers must consider.

 Huanuo Industrial Co., Ltd. is a Chinese factory that produces and develops USB cables, USB charger adapters, power adapters, TWS Bluetooth headsets and power chargers.  We provide customized USB cables, wholesale USB sync and charging cables, and travel USB chargers.

 Talking about TYPE C, Apple definitely can’t get around it. Apple has always been more aggressive in the interface of its own products. Since Apple launched a new MacBook Pro using TYPE C, the USB Type-C interface has quickly become popular among the public.  , From mobile phones, cameras, tablets, and even cars have begun to apply in batches (USB Type-C has achieved significant progress in the automotive field), today we will analyze this USB Type-C from a hardware perspective, and you may  Understand why this interface is so popular.

 The picture size is small, supports positive and negative insertion, and high speed (10Gb).  This small is for the USB interface on the previous computer, which is actually a bit bigger than the microUSB on the android machine:


 USB Type-C: 8.3mmx2.5mm

 Micro USB: 7.4mmx2.35mm

 And lightning: 7.5mmx2.5mm

 Therefore, I don't see the advantages of USB Type-C on handheld devices from the size.  The speed depends on whether the video transmission is needed.

 Pin definition

 It can be seen that data transmission mainly has TX / RX differential signals. CC1 and CC2 are two key pointers, which have many functions:

 Detect connection, distinguish front and back, distinguish DFP and UFP, that is, master-slave

 Configure Vbus, there are two modes: USB Type-C and USB Power Delivery

 Configure Vconn. When there is a chip in the cable, one cc transmits the signal, and one cc becomes the power supply Vconn

 Configure other modes, such as when connecting audio accessories, dp, pcie

 There are 4 power and ground, which is why it can support up to 100W.

 Don't look at the USB Type-C as if it can support up to 20V / 5A. In fact, this requires USB PD, and supporting USB PD requires an additional pd chip, so don't think that the USB Type-C interface can support up to 20V / 5A.  Talking about the origin and specifications of PD fast charging

 Of course, there should be integrated chips in the future.

 Auxiliary signals sub1 and sub2 (used by sideband) are only used in certain transmission modes.

 d+ and d- are compatible with previous standards of USB.

 Here to talk about, USB3.0 has only one RX/TX, the speed is 5Gb, USB Type-C can be inserted in order to ensure that the front and the back can be replaced, but in fact, data transmission still only uses a set of RX/TX, the speed is just  It has reached 10Gb.  If the protocol is upgraded later, the initialization will be the same 20Gb as DisplayPort.  Don’t be silly and confused, the USB interface is widely shared

work process

In the above figure, DFP (Downstream Facing Port) is the master, and UFP (Upstream Facing Port) is the slave.  In addition to DFP and UFP, there is also a DRP (Dual Role port). DRP can be used as DFP or UFP.  When DPR is connected to UFP, DRP is converted to DFP.  When DRP is connected to DFP, DRP is converted to UFP.  If two DRPs are connected together, then either one is DFP and the other is UFP.

There is a pull-up resistor Rp on the CC pin of the DFP, and a pull-down resistor Rd on the UFP.  When not connected, DFP's VBUS is not output.  After the connection, the CC pin is connected, and the CC pin of the DFP will detect the pull-down resistance Rd of the UFP, indicating that it is connected, and the DFP will turn on the Vbus power switch and output the power to the UFP.  And which CC pin (CC1, CC2) detects the pull-down resistance to determine the direction of interface insertion, and switch RX/TX by the way.

The resistance Rd=5.1k, and the resistance Rp is an uncertain value. According to the previous figure, you can see that there are several power supply modes for USB Type-C. What is the difference?  Relying on the value of Rp, the value of Rp is different, the voltage detected by the CC pin is different, and then to control which power supply mode the DFP side implements.

It should be noted that there are two CCs in the picture above, but there is actually only one CC line in the cable without a chip.  Type-C technical parameters graphic update release

The cable containing the chip is not two cc wires, but one cc and one Vconn, which are used to power the chip in the cable (3.3V or 5V). At this time, there is no pull-down resistor Rd at the cc terminal, but  Pull-down resistance Ra, 800-1200 ohms.

When both CC pins are connected to pull-down resistors <=Ra, DFP enters the audio accessory mode, and the left and right channels and mic are all available.

USB Type-C and DisplayPort, PCIE

USB PD is a BMC-encoded signal, while the previous USB is FSK, so there is incompatibility. I don’t know if there are products that can be converted on the market.

USB PD is transmitted on the CC pin. The PD has a VDM (Vendor defined message) function, which defines the device ID. When a device that supports DP or PCIe is read, the DFP enters the alternate mode.

If DFP recognizes that the device is DP, it will switch MUX/Configuration Switch and change the Type-C USB3.1 signal pin to transmit DP signal.  AUX auxiliary is transmitted by SBU1 and SUB2 of Type-C.  HPD is a detection pin, which is similar to CC, so it is shared.

And DP has four sets of differential signals lane0-3, Type-C has four sets of differential signals RX/TX1-2, so it is no problem to replace them completely.  And in the alternative mode in the DP protocol, USB signal and DP signal can be transmitted at the same time, RX/TX1 transmits USB data, RX/TX2 is replaced with lane0,1 two sets of data transmission, at this time, it can support up to 4k.

If DFP recognizes that the device is a DP, it switches the MUX/Configuration Switch to change the Type-C USB3.1 signal pin to transmit PCIe signals.  Similarly, PCIe uses RX/TX2 and SBU1, SUB2 to transmit data, and RX/TX1 transmits USB data.

The advantage of this is that one interface uses two devices at the same time. Of course, the conversion line can be done without any chips.  Type-C CC logic chip and wiring principle with E-MARK

Summarize our understanding

USB Type-C puts an end to the long-standing shortcomings of USB plugging in and out, saving people a lot of time. Change the direction for at least 2s. According to 1 billion people in the world plug and unplug a USB once a day, there is a 50% probability that it will be incorrectly inserted, and it takes time.  Over 277,000 hours, about 31 years, it’s horrible. One interface handles three types of audio and video data, and the volume is fairly small.  It is foreseeable that the Android device can be changed to the USB Type-C interface in the future. If only USB2.0 is needed, only the cable needs to be redone, and the chip is not used. The cost is completely negligible. As for Apple’s godson, Intel’s pro  Son, the positioning of the Thunderbolt interface in the TYPE C interface, I will continue to talk to you tomorrow, or you can read historical articles, first take a look: What is the difference between USB4.0 and Thunderbolt 4 interface; USB4, Thunderbolt 4 coaxial cable processing technology  share it

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