Ten Daily Electronic Common Sense-Section 4

What are the performances of USB2.0 high-speed OTG?

Compliant USB 2.0 specification OTC; supplementary protocol; running at high speed (480 Mbps), full speed (12 Mbps, for devices only) and low speed (1.5 Mbps, for host only) mode; support UTMI Level 3 interface; supportSession request protocol and host negotiation protocol; on the AHB bus.

What are the excitation methods of stepper motors?

The excitation method includes one-phase (one-way) excitation, two-phase (two-way) excitation, and two-phase (one-way) three excitation methods.

What are the adjustment methods of the switching power supply?

There are: PFM, PWM, chargepump, FPWM, PFM / PWM and pulse-skipPWM, digital PWM.Common among them are PFM, PWM, chargepump and PFM/PWM.

What are the advantages of the PHWS/PHWD wind speed and direction sensor?

It has the advantages of large measuring range, good linearity, strong anti-lightning capability, convenient observation, stable and reliable, etc. It can be widely used in meteorology, ocean, environment, airport, port, laboratory, industry, agriculture and transportation.

What are the main features of the MFRC500?

1. A highly integrated modulation and demodulation circuit.
2. The output buffer driver is connected to the antenna through a small number of external passive components with a maximum working distance of 10 cm.
3. Support IS0/IEC l4443-1~4 Type A protocol.
4. The CRYPT0 1 encryption algorithm and the internal key E2PROM memory are used.
5. The leading end of the chip is compatible with MFRC530, MFRC531, SLRC400 and MFRC632.
6. Parallel Microprocessor Interface with Internal Address Latch and IRQ Interrupt Request Line.
7. Programmable interrupt handling, timers and initialization configuration.
8. 64-byte receive/transmit FIFO (first-in, first-out) buffer.
9. 64-byte control register.
10. The digital, analog, and transmitting sections are separately powered by independent terminals, and have various power saving modes.
11. The internal oscillation buffer is connected to a 13.56 MHz quartz crystal oscillator.
12. Frame structure oriented to bits or bytes.
13. Support anti-collision operations.

What type of attribute protocol data unit is there?

• Request: The PDU that the client sends to the server and invokes the response.
• Response: The PDU sent by the server to the client responds to a request.
• Command: The PDU that the client sends to the server.
• Notification: The PDU that the server sent to the client without request.

What is a mesh topology?

The simplest network topology is a star network.The tree network topology is more flexible, but it is more difficult to implement.The last network topology is mesh.Mesh networks are complex but robust.The WirelessHART network is a flexible, self-organizing mesh network organization.Each device that initiates and aggregates messages is a router.The WirelessHART standard can be adapted to different applications and environments, and there are no special engineering or installation requirements that cover a large geographic area.

How does the magnetic field affect the current?

The magnetic field acts on the current in it.The unit of magnetic induction 曰 is Tesla (T), the unit of current intensity is ampere (A), and the unit of length Z is meter (m).

What is one of the main selling points of low-power Bluetooth?

One of the main selling points is the ability to power a low-power Bluetooth chip with a button battery, combined with a miniature sensor to create a variety of embedded or wearable sensor and sensor network applications.

What are the main reasons for using differential pair wiring?

1. for matching externally balanced differential transmission lines. In this case, the line-to-line coupling is irrelevant. Although two separate 50 Ω traces will couple the signal into a 100 Ω differential pair, this application is only to ensure that the transmitted signal is purely differential and that there are no common-mode components on the transmission line. The impedance of the two traces to ground must be equal, that is, they need to be symmetrical and not physically close to each other.
2. To avoid ground potential bounce. Differential components have built-in voltage references. A receiver connected to a differential pair transmission line does not need to rely on an external zero-volt reference, which is often degraded by ground bounce or noise interference voltages generated by the transmitting element. So it is only necessary to provide the receiver with two signals of equal amplitude, opposite polarity and the same delay from the transmitter. Here, too, the wiring is not required to be particularly close.
3. To reduce EMl. Because the magnetic flux travels in opposite directions on the two immediately adjacent wires, the magnetic fluxes on the tracks cancel each other out, resulting in a significant reduction in radiation. This cancellation effect is proportional to the ratio of S/D, where S is the line spacing, and D is the distance to the receiving antenna. For the FCC’s Class B limit requirements, at a distance of 3m (117in or 297cm), a 1in (2.54cm) line spacing will reduce EMl by 40dB, and a 0.10in (0.25cm) spacing will reduce 60dB. These attenuation values are better than using a common-mode balanced circuit at the two output ports that generate the differential signal. For the 0.10in spacing, we have balanced the non-ideal signal output by the source driver as well as possible. The line spacing is on the order of 0.10in, which reduces radiation so that it is well below the FCC limit. Therefore, for EMl, the differential line spacing of 0.10in is sufficient, and we do not need to make efforts to arrange the traces smaller than this spacing.
4. To reduce local crosstalk (10calized crosstalk). Differential lines in the PCB are less effective for reducing crosstalk. Usually the signals cancel each other out by the line spacing. A function of the ratio of s to the distance D from the antenna. So for local interference, this cancellation effect is minimal. For differential mode signals, the best way to improve local crosstalk is to keep the traces that interact with each other away. Assuming a stable power and ground reference plane, the crosstalk between the interfered line and the interfered line will be attenuated by the square of the distance between them. If the distance is doubled, the crosstalk is reduced by a factor of four. Two traces of a differential pair placed close together can increase crosstalk. The benefits of increasing the distance between the interferer and victim lines are more favorable than the proximity of the differential lines to each other.
5. Improve the efficiency of PCB routing. Differential lines can be placed nearby, which significantly improves routing efficiency and saves costs. The purpose of densely arranging lines is usually to save circuit board area. If tight differential wiring is used, two points need to be paid attention to: A newly printed line width must be calculated to compensate for the drop in differential mode impedance caused by the proximity of signal lines to each other. Once the signal lines are differential pairs, they should not be separated. Separation from each other causes changes in the line impedance unless wider lines are used. The second effect of placing lines side by side is that they can lead to poor wiring. If the lines are not allowed to separate, it will be difficult to handle when the lines encounter obstacles. The form of upper and lower wiring is generally a good solution to long-distance complex wiring.