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Continual Pressure/Temperature Monitoring (run on a cronjob)
# I didn't write this code. I just found it online.
# make sure to install python-smbus using below command
# sudo apt-get install python-smbus
import smbus
import time
from ctypes import c_short
DEVICE = 0x77 # Default device I2C address
#bus = smbus.SMBus(0) # Rev 1 Pi uses 0
bus = smbus.SMBus(1) # Rev 2 Pi uses 1
def convertToString(data):
# Simple function to convert binary data into
# a string
return str((data[1] + (256 * data[0])) / 1.2)
def getShort(data, index):
# return two bytes from data as a signed 16-bit value
return c_short((data[index] << 8) + data[index + 1]).value
def getUshort(data, index):
# return two bytes from data as an unsigned 16-bit value
return (data[index] << 8) + data[index + 1]
def readBmp180Id(addr=DEVICE):
# Chip ID Register Address
REG_ID = 0xD0
(chip_id, chip_version) = bus.read_i2c_block_data(addr, REG_ID, 2)
return (chip_id, chip_version)
def readBmp180(addr=0x77):
# Register Addresses
REG_CALIB = 0xAA
REG_MEAS = 0xF4
REG_MSB = 0xF6
REG_LSB = 0xF7
# Control Register Address
CRV_TEMP = 0x2E
CRV_PRES = 0x34
# Oversample setting
OVERSAMPLE = 3 # 0 - 3
# Read calibration data
# Read calibration data from EEPROM
cal = bus.read_i2c_block_data(addr, REG_CALIB, 22)
# Convert byte data to word values
AC1 = getShort(cal, 0)
AC2 = getShort(cal, 2)
AC3 = getShort(cal, 4)
AC4 = getUshort(cal, 6)
AC5 = getUshort(cal, 8)
AC6 = getUshort(cal, 10)
B1 = getShort(cal, 12)
B2 = getShort(cal, 14)
MB = getShort(cal, 16)
MC = getShort(cal, 18)
MD = getShort(cal, 20)
# Read temperature
bus.write_byte_data(addr, REG_MEAS, CRV_TEMP)
time.sleep(0.005)
(msb, lsb) = bus.read_i2c_block_data(addr, REG_MSB, 2)
UT = (msb << 8) + lsb
# Read pressure
bus.write_byte_data(addr, REG_MEAS, CRV_PRES + (OVERSAMPLE << 6))
time.sleep(0.04)
(msb, lsb, xsb) = bus.read_i2c_block_data(addr, REG_MSB, 3)
UP = ((msb << 16) + (lsb << 8) + xsb) >> (8 - OVERSAMPLE)
# Refine temperature
X1 = ((UT - AC6) * AC5) >> 15
X2 = (MC << 11) / (X1 + MD)
B5 = X1 + X2
temperature = int(B5 + 8) >> 4
temperature = temperature / 10.0
# Refine pressure
B6 = B5 - 4000
B62 = int(B6 * B6) >> 12
X1 = (B2 * B62) >> 11
X2 = int(AC2 * B6) >> 11
X3 = X1 + X2
B3 = (((AC1 * 4 + X3) << OVERSAMPLE) + 2) >> 2
X1 = int(AC3 * B6) >> 13
X2 = (B1 * B62) >> 16
X3 = ((X1 + X2) + 2) >> 2
B4 = (AC4 * (X3 + 32768)) >> 15
B7 = (UP - B3) * (50000 >> OVERSAMPLE)
P = (B7 * 2) / B4
X1 = (int(P) >> 8) * (int(P) >> 8)
X1 = (X1 * 3038) >> 16
X2 = int(-7357 * P) >> 16
pressure = int(P + ((X1 + X2 + 3791) >> 4))
#pressure = float(pressure / 100.0)
altitude = 44330.0 * (1.0 - pow(pressure / 101325.0, (1.0/5.255)))
altitude = round(altitude,2)
return (temperature,pressure,altitude)
#! /usr/bin/env python3
import bmp
import os.path
import sqlite3
import time
# This script runs and collects a single reading, writes it to a db, then exits
db_path = os.path.expanduser('~/data/temp-and-pressure/readings.db')
"""
CREATE TABLE readings(
id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
temperature NUMERIC,
pressure NUMERIC,
altitude NUMERIC,
created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
);
"""
def main():
temp, pressure, altitude = bmp.readBmp180()
connection = sqlite3.connect(db_path)
cursor = connection.cursor()
print(f'inserting into main.readings (t: {temp}, p: {pressure}, a: {altitude})')
cursor.execute(
'insert into main.readings (temperature, pressure, altitude) values (?, ?, ?)',
(temp, pressure, altitude),
)
connection.commit()
connection.close()
if __name__ == '__main__':
main()
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