Brainy Pi

Available to select audience (currently beta)

BrainyPi

GPIO Examples

Description

This page shows additional examples for interacting with BrainyPi GPIO.

INFO
This documentation is for Rbian OS version: 0.7.2-beta
To check the version of Rbian run the command in terminal
				
					os-version
Note: If the command fails or gives error then Rbian version is < 0.7.2-beta.

Example 1: ADXL345 I2C sensor on BrainyPi

1. Connect sensor according to the diagram below:
2. Porting I2C sensor code from RaspberryPi to BrainyPi

DIFF FROM RASPBERRYPI
To port Raspberry Pi code to BrainyPi you need to only change the I2C Port number from 1 (RaspberryPi) to 7 (BrainyPi).

3. Example code is given below. Copy the code to a file and name it adxl345.py.
				
					import smbus
from time import sleep

# I2C port for BrainyPi is 7. (/dev/i2c-7)
I2C_PORT = 7
bus = smbus.SMBus(I2C_PORT)

# ADXL345 constants
EARTH_GRAVITY_MS2   = 9.80665
SCALE_MULTIPLIER    = 0.004

DATA_FORMAT         = 0x31
BW_RATE             = 0x2C
POWER_CTL           = 0x2D

BW_RATE_1600HZ      = 0x0F
BW_RATE_800HZ       = 0x0E
BW_RATE_400HZ       = 0x0D
BW_RATE_200HZ       = 0x0C
BW_RATE_100HZ       = 0x0B
BW_RATE_50HZ        = 0x0A
BW_RATE_25HZ        = 0x09

RANGE_2G            = 0x00
RANGE_4G            = 0x01
RANGE_8G            = 0x02
RANGE_16G           = 0x03

MEASURE             = 0x08
AXES_DATA           = 0x32

class ADXL345:

    address = None

    def __init__(self, address = 0x53):        
        self.address = address
        self.setBandwidthRate(BW_RATE_100HZ)
        self.setRange(RANGE_2G)
        self.enableMeasurement()

    def enableMeasurement(self):
        bus.write_byte_data(self.address, POWER_CTL, MEASURE)

    def setBandwidthRate(self, rate_flag):
        bus.write_byte_data(self.address, BW_RATE, rate_flag)

    # set the measurement range for 10-bit readings
    def setRange(self, range_flag):
        value = bus.read_byte_data(self.address, DATA_FORMAT)

        value &= ~0x0F;
        value |= range_flag;  
        value |= 0x08;

        bus.write_byte_data(self.address, DATA_FORMAT, value)
    
    # returns the current reading from the sensor for each axis
    #
    # parameter gforce:
    #    False (default): result is returned in m/s^2
    #    True           : result is returned in gs
    def getAxes(self, gforce = False):
        bytes = bus.read_i2c_block_data(self.address, AXES_DATA, 6)
        
        x = bytes[0] | (bytes[1] << 8)
        if(x & (1 << 16 - 1)):
            x = x - (1<<16)

        y = bytes[2] | (bytes[3] << 8)
        if(y & (1 << 16 - 1)):
            y = y - (1<<16)

        z = bytes[4] | (bytes[5] << 8)
        if(z & (1 << 16 - 1)):
            z = z - (1<<16)

        x = x * SCALE_MULTIPLIER 
        y = y * SCALE_MULTIPLIER
        z = z * SCALE_MULTIPLIER

        if gforce == False:
            x = x * EARTH_GRAVITY_MS2
            y = y * EARTH_GRAVITY_MS2
            z = z * EARTH_GRAVITY_MS2

        x = round(x, 4)
        y = round(y, 4)
        z = round(z, 4)

        return {"x": x, "y": y, "z": z}

if __name__ == "__main__":
    # if run directly we'll just create an instance of the class and output 
    # the current readings
    adxl345 = ADXL345()
    
    while True:
        axes = adxl345.getAxes(True)
        print("=======================")
        print("x-axis = %.3fG" % ( axes['x'] ))
        print("y-axis = %.3fG" % ( axes['y'] ))
        print("z-axis = %.3fG" % ( axes['z'] )) 
        sleep(1)
4. Run command to execute the code
				
					sudo python3 adxl345.py

Example 2: BMP280 I2C sensor on BrainyPi

1. Connect sensor according to the diagram below:
2. Porting I2C sensor code from RaspberryPi to BrainyPi

DIFF FROM RASPBERRYPI
To port Raspberry Pi code to BrainyPi you need to only change the I2C Port number from 1 (RaspberryPi) to 7 (BrainyPi).

3. Example code is given below. Copy the code to a file and name it tempsensor.py.
				
					import smbus2
import bme280 as sensor
import time

# I2C port for BrainyPi is 7. (/dev/i2c-7)
I2C_PORT = 7
BME280_ADDR = 0x76

bus = smbus2.SMBus(I2C_PORT)
calibration_params = sensor.load_calibration_params(bus, BME280_ADDR)

# the sample method will take a single reading and return a
# compensated_reading object
while True:
    data = sensor.sample(bus, BME280_ADDR, calibration_params)

    print("=======================")
    print("Time:", data.timestamp)
    print("Temperature: %f deg C" % data.temperature)
    print("Pressure: %f hPa" % data.pressure)
    time.sleep(1)
4. Run command to execute the code
				
					sudo python3 tempsensor.py
NEED SUPPORT?
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