μSharp Patch Data Format -- UART

The standard UART protocol is used for our serial transmission interface. The protocol can be modified based on your specific requirement. Contact us to request a change in protocol or other requirements you may have with your system.

Communication Protocol

The communication protocol is:

Standard UART
Baud rate is 115200 b/s
Data length is 8 bits, plus one start bit and one stop bit, and no parity bit
I/O standard is 3.3V LVTTL

725 — user interface on μSharp Patch for UART

Data Format for Serial Transmission Interface

The packet of output data consists of 6 Bytes. The byte structure is explained below. Note that an 'x' refers to a variable bit containing dynamic data.


Byte 1	0xFE	Packet Header
Byte 2	0x01	Version ID
Byte 3	0bxxxxxxxx	Distance (Least Significant 8 Bits)
Byte 4	0bxxxxxxxx	Distance (Most Significant 8 Bits)
Byte 5	0bxxxxxxxx	SNR (signal to noise ratio)
Byte 6	0bxxxxxxxx	Checksum (formula below)

Explanation

Distance

The distance bytes can be combined (totally 16 bits) to represent the distance information in centimeters. The structure would be: 0x[MSB][LSB], where MSB and LSB are each two hexadecminal numbers (8 bits).

Note: When distance returns 0, it to mean 'no target detected' or 'infinity'.

SNR

The altitude reading will be associated with SNR ( range from 0 to 60 ) to indicate the quality of the reflections.

Checksum

The Checksum Byte could be used in the following check code:

if (Version_ID + Distance_H + Distance_L + SNR) & 0xFF == checksum
is_valid = 1 (check passed)
else
is_valid = 0 (failed)

Example Python 2.7 Code for receiving/showing data on PC

Note: Please download necessary Python package before running this example script.

from serial import Serial
import struct
import matplotlib.pyplot as plt

serial = Serial('COM7', 115200,8, 'N',1)   ### This serial port may be various on different machines
serial.flushInput()
serial.flushOutput()

while(1):
  byte = struct.unpack('B', serial.read(1))[0]
  if(byte == 0xFE):
    byte2 = struct.unpack('B', serial.read(1))[0]
    byte3 = struct.unpack('B', serial.read(1))[0]
    byte4 = struct.unpack('B', serial.read(1))[0]
    byte5 = struct.unpack('B', serial.read(1))[0]
    byte6 = struct.unpack('B', serial.read(1))[0]
    header = byte
    version_id = byte2
    lsb_byte = byte3
    msb_byte = byte4
    snr = byte5
    check_sum_transmitter = byte6   
    check_sum_receiver = (byte2 + byte3 + byte4 + byte5) & 0xFF
    DISTANCE = byte3 + (byte4<<8)
        
   ### Print received data
    if (check_sum_receiver == check_sum_transmitter):
      print "checksum passed, DISTANCE:  " + str(DISTANCE) + ", SNR:" + str(snr) + '\r\n'
    else:
      print "checksum failed!!!" + '\r\n'
  else:
    continue

Example Arduino Code for receiving/showing data on PC

Note: Please install Arduino IDE before running this example script.

// This function is called only once, at reset.
void setup() {
  Serial.begin(115200);
  Serial.println("uSharp Patch Readout"); 
}

// This function is called continuously, after setup() completes.
void loop() {
  int altitude = 0;
  int data[64];
  int data_packet[6];
  int idx;
  int receiver_checksum;
  int SNR;

    /// Buffer size = default 64 Bytes, this depends on Arduino board setting!
    while (Serial.available() == 63) {
      delay(20);
      for(int i=0;i<64;i++){
        data[i]=Serial.read();
      }
      for (int j=0;j<12;j++){
        if (data[10+j] == 0xFE && data[10+j+1] == 0x01){
          idx = j;
          break;
        }
      }
      data_packet[0] = data[10+idx];
      data_packet[1] = data[11+idx];
      data_packet[2] = data[12+idx];
      data_packet[3] = data[13+idx];
      data_packet[4] = data[14+idx];
      data_packet[5] = data[15+idx];
      altitude = data_packet[2] + (data_packet[3] << 8);
      SNR = data_packet[4];
      receiver_checksum = (data_packet[1] + data_packet[2] + data_packet[3] + data_packet[4]) & 0xff;
      
      /// Print received data
      if (receiver_checksum == data_packet[5]){
        Serial.print("Checksum passed, ALTITUDE: ");
        Serial.print (altitude);
        Serial.print(",  SNR: ");
        Serial.print (SNR);
        Serial.print("\n\r");          
      }else{
        Serial.print ("Checksum failed!!!");
        Serial.print("\n\r");          
      }             
    }
}