一 : 《与妻书》参考资料
1 .课文解读。二 : 费星:费星-专辑,费星-参考资料
姓名:费星费星性别:女英文名:FeiXing。
姓名:费星
费星性别:女
英文名:FeiXing
费星_费星 -专辑
专辑名称:紫惑
费星歌手:费星
语言:国语
风格:流行/Pop发烧音乐/HiF
i唱片公司:耀星唱片
发行日期:2006-11-22
费星_费星 -参考资料
一听音乐三 : 卖楼花:卖楼花-参考资料
卖楼花,房地产经营手法,霍英东始创,是指在楼宇只有设计图纸,没有正式动工之前,买家先交订金预购楼房。
在楼宇只有设计图纸,没有正式动工之前,买家先交订金预购楼房,就像在果树开花阶段,买家交钱买那个“花”,然后在花结成果时再摘那个“果实”一样,于是香港人就把正在兴建中或计划兴建还没有动工的楼宇或其中的单元,形象地喻为“楼花”;霍英东提出预购“楼花”,就是“卖楼花”。“卖楼花”如今已成为全球地产行业都使用的经营手法,而霍英东则是这一方法的发明者和第1个推行的人。“卖楼花”加速了楼宇的销售,加快资金回收;且收足买楼者预付的订金后才动工兴建楼宇,也避免投资风险。卖楼花_卖楼花 -参考资料
1霍英东始创“卖楼花”财经界论文四 : TIDA-00151技术参考资料
Automotive Ultrasonic Sensor Interface for Park Assist or Blind Spot Detection Systems - Test Data
This document shares the tests results of the PGA450-Q1with a Murata sensor (MA58MF14-0N).
The data is structured into two main categories:
1.
2.
3.
4. Test set up Test strategy Power Considerations Test data
Equipment used to create this data:
1. PGA450-Q1 EVM + TI communication (TIger) board
2. PC with the PGA450-Q1 EVM GUI installed
3. 5V power supply
Section 1: Test set up
Before the system is powered up, please make sure all hardware is configured properly. Check that all jumpers and headers are connected appropriately. For a detailed description of configurations, see EVM user’s guide.
To power the board:
1. Only one main power supply is needed. Apply 7 VDC to 18 VDC to the PGA450-Q1EVM that supplies power to the entire board, except for the USB
communications board and LIN which are powered by the USB communication PCB (TIger board).
2. Connect a power supply to the banana jacks, P1 “VPWR_IN” and P3 “GND” or use the screw terminal P2.
3. As stated prior, the TI communication board (TIger) supplies 5V to portions of the hardware and also connects the EVM to the PC. For the TIger board to supply 5V, make sure the “Jumper 5V” is connected (default settings). This board could be replaced by an MSP430 launchpad that connects to PC through USB.
To test functionality of board:
1. Connect the PGA450-Q1 EVM to the interface board. Connect the interface board to a PC. Install the PGA450-Q1 GUI.
2. A Murata transducer is included with the EVM. Solder the transducer connector to the through-holes at P6. Alternatively, use the screw terminal to connect the transducer.
3. To program OTP bits, program registers, then take data, see PGA450-Q1 EVM user’s guide.
Section 2: Test strategy
The PGA450 parameters can be optimized for either short distance measurements or long distance measurements. Automotive grade waterproof transducers must be driven with large voltages to generate a sound wave with enough SPL (Sound Pressure Level) to survive the attenuation due to air, and the scattering and absorption that occurs when the sound wave reflects off of an object, to still be strong enough to excite the transducer upon its return.
To detect at a maximum distance, it is necessary to create the highest SPL possible, and to have a high degree of granularity after the signal processing stage of the
PGA450 IC. For short distances, it is imperative Below is an overview of the settings on the PGA450 and how to optimize them for short and long distance measurements.
? Number of bursts (PULSE_CNTA, PULSE_CNTB)
o This setting controls the number of times that the low side drivers switch
on and off.
o Short distance optimization: Reduce this to the minimum number of
bursts, 1. This still excites the transducer enough to generate a good
sound wave, and it minimizes the time needed for the drive energy
resonating in the transducer to decay.
o Long distance optimization: When attempting to measure longer
distances, the decay time of the drive signal is not as important, so
increase the number of bursts to create a stronger and longer duration
signal with a higher SPL. The setting used for testing was 18 pulses.
? Blanking timer (BLANKING_TMR)
o The blanking timer waits a specified amount of time before starting data
collection into the FIFO RAM. Increasing the blanking timer will increase
the maximum possible distance that can be measured (since there is a
finite amount of memory in the FIFO). It also helps mask the section of
the data where the returned signal is saturated since that does not give
any useful data.
o Short distance optimization:
o Long distance optimization:
? Bits to store in the FIFO (FIFO_CTRL)
o The digital datapath has 12 bits of resolution, but storing all 12 bits would
fill up the 768 bytes of RAM allocated for capturing the echo signal quickly.
There are four options for which bits to save to the FIFO: all 12 bits, the 8
most-significant bits, the 8 least-significant bits, and the 8 middle bits.
o Short distance optimization: The echo signal is stronger at short distances, well above the noise floor. To achieve the minimum distance, it’s more
important to reduce the length of time that the data is saturated, which
makes using the 8 most-significant bits the optimum choice.
o Long distance optimization: The farther away an object is, the weaker the returned echo signal. This means that the extra resolution is important
when attempting to distinguish the signal from the noise floor. Using the 8
least-significant bits is the optimum choice for long distance
measurements.
The test object for the data shown below is a 1m tall, 76mm diameter PVC pipe. The transducer was placed 40cm above the ground and testing was completed outside on concrete.
The transducer used is the MA58MF14-0N.
Section 3: Power Considerations
This particular application is only on and consequently consuming power, when the car is on. In applications where the PGA450-Q1 is always on, even when the car is turned off, careful measures must be taken to consider power consumption.
There are three general modes of operation that the PGA450 will cycle between during operation, quiet mode, active mode, and VREG charging mode. The data below is from the PGA450Q1 datasheet and is at VPWR = 18V.
The length of time that the VREG capacitor needs to charge will depend on how much it was depleted during the bursting (which will depend on the transducer/transformer components used and the number of bursts). With the components on the TI EVM, recovering from 18 bursts (long distance mode) takes about 5ms to charge, and 1 burst (short distance mode) takes about 1ms to charge.
The time of flight for an ultrasonic signal to reach an object 6m away and return takes about 35ms in air at room temperature (TOF = distance/v = 12m/(343m/s)). The length of time between measurements is dependent on the application. For this example, assume that another 35ms is spent in quiet mode between measurements and that the long distance mode is being used. This is a worst case measurement since maximum current values are being used instead of typical.
Section 4: Test Data
Figure X1 shows data from six separate runs with a 1m tall, 76mm wide PVC pipe placed various distances away from the PGA450. The amplitude refers to the signal strength of the echo signal after it goes through the signal processing steps on the PGA450 (LNA, ADC, BPF, peak extractor, and downsampling). When the echo signal exceeds the programmable threshold, the PGA450 recognizes that an object was detected and records a time of flight. This time of flight can be converted to a distance by knowing the speed of sound. The division by two is because the sound wave must travel to the object and then back again.
Figure X1 – Test data for long distance measurements
Figure X2 shows data taken in the short distance mode from three separate runs.
Figure X2 – Test data for short distance measurements
See the referenced example code to see how to program the PGA450 8051 microcontroller to process the FIFO RAM to extract distance information.
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