Feature
Small size, supports reversible insertion, and fast speed (10Gb). This small one is based on the USB interface on the previous computer. In fact, it is a bit larger than the microUSB on the Android machine:
USB Type-C：8.3mmx2.5mm
microUSB：7.4mmx2.35mm
And lightning: 7.5mmx2.5mm
So, I don't see the advantage of USB Type-C on handheld devices in terms of size. As for speed, it only depends on whether video transmission is needed.
Pin definition
It can be seen that data transmission mainly includes two sets of differential signals TX/RX. CC1 and CC2 are two key pins and have many functions:
• Detect connections, distinguish front and back, distinguish DFP and UFP, that is, master-slave
• Configure Vbus, with two modes: USBType-C and USB Power Delivery
• Configure Vconn. When there is a chip in the cable, one cc transmits signals and one cc becomes the power supply Vconn.
• Configure other modes, such as when connecting audio accessories, dp, pcie
There are 4 power supplies and ground, which is why it can support up to 100W.
Don’t look at 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..
Of course, integrated chips should appear in the future.
Auxiliary signals sub1 and sub2 (Side band use) are only used in certain transmission modes.
d+ and d- are compatible with pre-USB standards.
Let me talk about it here, USB3.0 only has one set of RX/TX, and the speed is 5Gb. USB Type-C uses two sets to ensure that both front and back can be plugged in, but in fact, only one set of RX/TX is used for data transmission. The speed has already reached 10Gb. If the protocol is upgraded later, if both groups are transmitted, it will be the same as DisplayPort at 20Gb..
work process
In the picture above, DFP (Downstream Facing Port) is the master, and UFP (Upstream Facing Port) is the slave. In addition to DFP and UFP, there is also DRP (DualRole 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 into UFP. When 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 DFP, and a pull-down resistor Rd on the UFP. When not connected, DFP's VBUS has no output. After connection, the CCpin is connected, and the CC pin of DFP will detect the pull-down resistor Rd of UFP, indicating that it is connected, and DFP will turn on the Vbus power switch and output power to UFP. Which CC pin (CC1, CC2) detects the pull-down resistor determines the direction of the interface insertion, and switches RX/TX by the way.
The resistance Rd=5.1k, and the resistance Rp is an uncertain value. According to the previous figure, we can see that USB Type-C has several power supply modes. How can we identify them? It depends on the value of Rp. If the value of Rp is different, the voltage detected by the CC pin is different, and then it controls which power supply mode the DFP side executes.
It should be noted that two CCs are drawn in the picture above. In fact, there is only one CC line in the cable without chip.
The cable containing the chip does not have two cc lines, 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 on the cc end, but Pull-down resistor Ra, 800-1200 ohms.
When both CC pins are connected to pull-down resistors <=Ra, the DFP enters the audio accessory mode, with both left and right channels and mic, as shown in the picture above.
USB Type-Cand DisplayPort, PCIE
USB PD is a BMC encoded signal, while the previous USB was FSK, so there is incompatibility. I don’t know if there are any products on the market that can convert it. USB PD is transmitted on the CC pin. PD has a VDM (Vendor defined message) function, which defines the device ID. When reading a device that supports DP or PCIe, DFP enters alternate mode. If DFP recognizes that the device is DP, it switches the MUX/Configuration Switch to change the Type-C USB3.1 signal pin to transmit DP signals. AUX assistance is transmitted by SBU1 and SUB2 of Type-C. HPD is the detection pin, which is similar to CC, so they are shared. DP has four sets of differential signals in lane0-3, and Type-C has four sets of differential signals in RX/TX1-2, so it is no problem to completely replace them. Moreover, in the alternative mode in the DP protocol, USB signals and DP signals can be transmitted simultaneously, RX/TX1 transmits USB data, and RX/TX2 is replaced by lane0,1 two sets of data transmission, which can support up to 4k at this time. If DFP recognizes that the device is DP, it switches the MUX/Configuration Switch so that the Type-C USB3.1 signal pin transmits the PCIe signal instead. 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 can use two devices at the same time. Of course, a conversion cable can do this without any chips.
Final Thoughts
USB Type-C ends the long-standing disadvantage of USB plugging in and out, saving people a lot of time. It takes at least 2 seconds to change the direction. According to 10 billion people in the world plugging and unplugging USB once a day, there is a 50% chance of plugging it in incorrectly, which takes a total of time. More than 277000 hours, about 31 years, which is terrifying.
One interface handles three types of audio and video data, and the size is quite small. It is foreseeable that Android phones can be changed to USB Type-C interface in the future. If you only need USB2.0, you only need to redo the cable without using a chip, and the cost is completely negligible.
