Ultrasonic sensor (ch101 & ch201) - Ⅱ

1. Preface

The last article simply introduced CH101/CH201 These two sensors . In addition to chips, this kind of sensor needs to be used , We also need an acoustic “ hat ”（FOV Horn）.
The configuration parameters of this sensor are through I2C The interface will External data （ Array ） Write on chip SOC Of . therefore , Sensors I2C There are two ways to read and write ： One is to read and write registers ,I2C The communication includes the slave address 、 Register address 、 data 、 Data length field . Another kind of primitive I2C, Only slave address 、 data 、 Data length . therefore , The configuration information of the sensor adopts Program Slave Pattern , The application parameters of the sensor are application slave （ That is, there are two slave addresses ,Program Slave Address, It's a chip reset Fixed address after : 0x45.application slave address, Every firmware init Function entry reset ）
About I2C Detailed operation of , More on that later

This kind of sensor emits ultrasonic pulse and measures the flight time of the pulse passing through the air (ToF) To measure the distance （ Range ）. The pulse is either reflected back to the transmitting sensor , Or received by a second sensor .
CHx01 The sensor is an ultrasonic transceiver , This means that it can send and receive ultrasonic signals . Different from other passive sensors ,CHx01 Actively send signals to the environment . For basic distance measurement , The sensor will send out a very short ultrasonic pulse . Then it will immediately enter “ listen ” state , In this state , It will sample the received sound , Try to identify the pulse echo reflected from a sensor . Objects near the sensor . If the ultrasonic pulse is recognized , The sensor will analyze the signal to determine the time , Then report the received pulse ToF. Then we can start from ToF Calculate the actual distance of ultrasonic wave .

2. Currently officially released Horn There are the following ：

3. ultrasonic TOF sensor VS Infrared sensors

Passive infrared sensor PIR（Passive infrared sensors） Characteristics ：

1. Widely used indoors
2. Integrated lens is needed to make the volume very large , Sensitive to heat and light
3. Unable to report distance information , Only moving objects can be detected
4. Insensitive to small movements

4. Develop evaluation suite