# L04 Underwater Sonar

![](Resources/sensors/L04-5.jpg)


[Datasheet](https://cdn-shop.adafruit.com/product-files/4664/4664_datasheet.pdf)

## Cable Descriptions
| Color      | Name       | Description       | Remarks | 
|------------|------------|-------------------|---------|
| red        | VCC Power  | input cable       | 3.3V~5V |
| black      | GND Power  | ground cable      | //      |
| white      | RX Trigger | input cable       | (1)     |
| yellow     | TX UART    | output cable      | (1)     |

## UART Data Frames
| Frame data   | Instruction   | Byte   |
|--------------|---------------|--------|
| Frame header | Fixed to 0xFF | 1 byte |
| Data_H High  | 8 bits of distance data | 1 byte
| Data_L Low   | 8 bits of distance data | 1 byte
| SUM          | Checksum of communication | 1 byte

```c
#include <SoftwareSerial.h>
unsigned char buffer_RTT[4] = {0};
uint8_t CS;
#define COM 0x55
SoftwareSerial mySerial(7, 8); 

void setup() {
  Serial.begin(115200);
  mySerial.begin(115200);
}

void loop() {
  mySerial.write(COM);
  delay(100);
  if(mySerial.available() > 0){
    delay(4);
    if(mySerial.read() == 0xff){    
      buffer_RTT[0] = 0xff;
      for (int i=1; i<4; i++){
        buffer_RTT[i] = mySerial.read();   
      }
      CS = buffer_RTT[0] + buffer_RTT[1]+ buffer_RTT[2];  
      if(buffer_RTT[3] == CS) {
        int distance = (buffer_RTT[1] << 8) + buffer_RTT[2];
        Serial.print("Distance:");
        Serial.print(distance);
        Serial.println("mm");
      }
    }
  }
}
```