Published January 8, 2016 © GPL3+

BeagleBone barometer

Example for using BeagleBone, Mikroelektronika Barometer click and Python

BeginnerProtip1,850

Things used in this project

Hardware components

BeagleBoard.org BeagleBone Black

MIKROE MicroBUS Cape

MIKROE Barometer click

Story

This article describe how to start with BeagleBone, Python and I2C devices.

For this example you need:

BeagleBone
MikroBUS Cape
Barometer click

To prepare BeagleBone you need to install python-smbus package. Adafruit_I2C library use this package.

I hope this small example is usefull for someone who start with Python programming and use Mikroelektronika click boards on BeagleBone

from Adafruit_I2C import Adafruit_I2C 


def twos_comp(val, bits):
    """compute the 2's compliment of int value val"""
    if (val & (1 << (bits - 1))) != 0: # if sign bit is set e.g., 8bit: 128-255
        val = val - (1 << bits)        # compute negative value
    return val
    
class BAROMETER_CLICK:

    address = None
    i2C = None
    WHO_AM_I = 0x0F
    PRESS_OUT_XL = 0x28
    PRESS_OUT_L = 0x29
    PRESS_OUT_H = 0x2A
    CTRL_REG1 = 0x20
    STATUS_REG = 0x27
    TEMP_OUT_L = 0x2B
    TEMP_OUT_H = 0x2C
    
    def __init__(self, address = 0x5D):
        self.address = address
        self.i2C = Adafruit_I2C(self.address)
        
    def whoAmI(self):
        reg_val = self.i2C.readU8(self.WHO_AM_I)
        return reg_val
        
    def setActive(self):
        reg_val = self.i2C.readU8(self.CTRL_REG1)
        reg_val = reg_val | 0x80
        self.i2C.write8(self.CTRL_REG1,reg_val)
        
    def Config(self):
        self.i2C.write8(self.CTRL_REG1,0xB0)
        
    def getStatus(self):
        reg_val = self.i2C.readU8(self.STATUS_REG)
        return reg_val
        
    def getTempC(self):
        reg_H = self.i2C.readU8(self.TEMP_OUT_H)
        reg_L = self.i2C.readU8(self.TEMP_OUT_L)
        res = (reg_H<<8) | (reg_L)
        res = twos_comp(res,16)
        res = res/480.0 + 42.5
        return res
        
    def getPressure(self):
        reg_XL = self.i2C.readU8(self.PRESS_OUT_XL)
        reg_L = self.i2C.readU8(self.PRESS_OUT_L)
        reg_H = self.i2C.readU8(self.PRESS_OUT_H)
        res = (reg_H << 16) | (reg_L << 8) | (reg_XL)
        res = twos_comp(res,24)
        return res/4096.0