Maxbotix Ultrasonic/Ultrasound sensor MB7137 for Lopy

[innovpoint]

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 :)

[jmarcelino]

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

[innovpoint]

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)