Maxbotix Ultrasonic/Ultrasound sensor MB7137 for Lopy



  • Hi,

    I have 1 sensor I2C MB7137 : (Datasheet: http://www.m axbotix.com/documents/XL-TrashSonar-WR_Datasheet.pdf)

    I need to mesure the distance with this sensor like on arduino:

    Arduino code resume:

    /* RANGE SENSOR */
    #define SensorAddress byte(0x70)            // send 112 address
    #define RangeCommand byte(0x51)             // send 81 address
    
    void setup(){
       configureRangeSensor()
    }
    
    void loop()
    {
    takeRangeReading()
    requestRange()
    }
    
    
    
    void configureRangeSensor(){
        //sensor:
        Wire.begin();
        delay(100);
    } 
    
    //Commands the sensor to take a range reading
    void takeRangeReading(){
           Wire.beginTransmission(SensorAddress);             //Start addressing 
           Wire.write(RangeCommand);                          //send range command 
           Wire.endTransmission();                            //Stop and do something else now
    } 
    //Returns the last range that the sensor determined in its last ranging cycle in centimeters. Returns 0 if there is no communication. 
    word requestRange(){ 
        Wire.requestFrom(SensorAddress, byte(2));
                if(Wire.available() >= 2){                   //Sensor responded with the two bytes 
               byte HighByte = Wire.read();                  //Read the high byte back 
               byte LowByte = Wire.read();                   //Read the low byte back 
               word range = word(HighByte, LowByte);     //Make a 16-bit word out of the two bytes for the range 
               return range; 
            }
            else { 
            return word(0);                                  //Else nothing was received, return 0 
        }
    } 
    

    I need to convert for python for lopy:

    My code not work:

    from time import sleep_ms
    from machine import I2C
    
    # Default Address
    MB7137_I2C_DEFAULT_ADDR = 0x70   #112 ADDRESS
    
    # Commands
    CMD_MEASURE_DISTANCE = 0x51 #81 ADDRESS
    
    
    i2c = I2C(0, I2C.MASTER, baudrate=250000)
    
    
    class MB7137(object):
      
      print ("start:")
    
      def __init__(self, i2c=None):
        self.i2c = i2c
        self.addr = MB7137_I2C_DEFAULT_ADDR
        self.cbuffer = bytearray(2)
        self.cbuffer[1] = 0x00
        
      def write_command(self, command_byte):
        print ("write:")
        self.cbuffer[0] = command_byte
        self.i2c.writeto(self.addr, self.cbuffer)
    
      def readDistance(self):
        print ("read:")
        self.write_command(CMD_MEASURE_DISTANCE)
        sleep_ms(25)
        dist = self.i2c.readfrom(self.addr, 3)
        dist2 = dist[0] << 8
        dist2 = dist2 | dist[1]
        return  dist
    
    
    sensor = MB7137()
    sensor.__init__(MB7137_I2C_DEFAULT_ADDR)
    sensor.write_command()
    sensor.readDistance()
    

    Help please :)



  • Ok..

    Solved:

    from machine import I2C
    import time

    ADDR = 0x70
    CMD = 0x51

    configure the I2C bus

    i2c = I2C(0, I2C.MASTER, baudrate=250000)

    i2c.writeto(ADDR, bytes([CMD]))
    time.sleep(0.5)
    dist = i2c.readfrom(ADDR, 2)
    total = (dist[0]*255)+dist[1]

    print(total)



  • Olá innovpoint!

    I don't have that sensor, but some suggestions:

    1. Lower your I2C speed, the sensor is very slow you don't to use a fast speed: i2c = I2C(0, I2C.MASTER, baudrate=100000) is enough

    2. In readDistrance you do sleep_ms(25) but the datasheet recommends waiting 100ms (the Arduino code polls for data, but not sure you have to)

    3. In your main code sensor.write_command() has no purpose, that's a function used by readDistance

    Hope this helps

    ps: I formatted up the code in your post, next time please use the forum Markdown syntax using ``` to start/end code blocks


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