Code: Select all
Scan i2c bus...
i2c devices found: 1
Decimal address: 118 | Hexa address: 0x76Code: Select all
I2C scan result : [118]
I2C connection successfull
Traceback (most recent call last):
File "<stdin>", line 22, in <module>
File "/lib/bmp280.py", line 97, in __init__
File "/lib/bmp280.py", line 126, in _read
OSError: [Errno 5] EIOCode: Select all
i2c=machine.I2C(0,sda=machine.Pin(bme_PinSDA), scl=machine.Pin(bme_PinSCL), freq=100000) #initializing the I2C method
bme = bme280.BME280(i2c=i2c,address=0x76)
Code: Select all
from bmp280 import *
from machine import Pin, I2C
import utime
from time import sleep
i2c = I2C(0, sda = Pin(16), scl = Pin(17), freq = 100000)
ERROR = -3 # hPa
# scan i2c port for available devices
result = I2C.scan(i2c)
print("I2C scan result : ", result) # 118 in decimal is same as 0x76 in hexadecimal
if result != []:
print("I2C connection successfull")
else:
print("No devices found !")
# create a BMP 280 object
bmp280_object = BMP280(i2c)
# configure the sensor
# These configuration settings give most accurate values in my case
# tweak them according to your own requirements
bmp280_object.power_mode = BMP280_POWER_NORMAL
bmp280_object.oversample = BMP280_OS_HIGH
bmp280_object.temp_os = BMP280_TEMP_OS_8
bmp280_object.press_os = BMP280_TEMP_OS_4
bmp280_object.standby = BMP280_STANDBY_250
bmp280_object.iir = BMP280_IIR_FILTER_2
print("BMP Object created successfully !")
utime.sleep(2) # change it as per requirement
print("\n")
# Function for calculation altitude from pressure and temperature values
# because altitude() method is not present in the Library
def altitude_HYP(hPa , temperature):
# Hypsometric Equation (Max Altitude < 11 Km above sea level)
temperature = temperature
local_pressure = hPa
sea_level_pressure = 1013.25 # hPa
pressure_ratio = sea_level_pressure/local_pressure # sea level pressure = 1013.25 hPa
h = (((pressure_ratio**(1/5.257)) - 1) * temperature ) / 0.0065
return h
# altitude from international barometric formula, given in BMP 180 datasheet
def altitude_IBF(pressure):
local_pressure = pressure # Unit : hPa
sea_level_pressure = 1013.25 # Unit : hPa
pressure_ratio = local_pressure / sea_level_pressure
altitude = 44330*(1-(pressure_ratio**(1/5.255)))
return altitude
while True:
# accquire temperature value in celcius
temperature_c = bmp280_object.temperature # degree celcius
# convert celcius to kelvin
temperature_k = temperature_c + 273.15
# accquire pressure value
pressure = bmp280_object.pressure # pascal
# convert pascal to hectopascal (hPa)
# 1 hPa = 100 Pa
# Therefore 1 Pa = 0.01 hPa
pressure_hPa = ( pressure * 0.01 ) + ERROR # hPa
# accquire altitude values from HYPSOMETRIC formula
h = altitude_HYP(pressure_hPa, temperature_k)
# accquire altitude values from International Barometric Formula
altitude = altitude_IBF(pressure_hPa)
press = "{:.2f}".format(pressure_hPa)
h_alti = "{:.2f}".format(h)
i_alti = "{:.2f}".format(altitude)
print("Temperature : ",temperature_c," Degree Celcius")
print("Pressure : ",pressure," Pascal (Pa)")
print("Pressure : ",press," hectopascal (hPa) or millibar (mb)")
print("Altitude (Hypsometric Formula) : ", h_alti ," meter")
print("Altitude (International Barometric Formula) : ", i_alti ," meter")
print("\n")
Code: Select all
from micropython import const
from ustruct import unpack as unp
# Author David Stenwall Wahlund (david at dafnet.se)
# Power Modes
BMP280_POWER_SLEEP = const(0)
BMP280_POWER_FORCED = const(1)
BMP280_POWER_NORMAL = const(3)
BMP280_SPI3W_ON = const(1)
BMP280_SPI3W_OFF = const(0)
BMP280_TEMP_OS_SKIP = const(0)
BMP280_TEMP_OS_1 = const(1)
BMP280_TEMP_OS_2 = const(2)
BMP280_TEMP_OS_4 = const(3)
BMP280_TEMP_OS_8 = const(4)
BMP280_TEMP_OS_16 = const(5)
BMP280_PRES_OS_SKIP = const(0)
BMP280_PRES_OS_1 = const(1)
BMP280_PRES_OS_2 = const(2)
BMP280_PRES_OS_4 = const(3)
BMP280_PRES_OS_8 = const(4)
BMP280_PRES_OS_16 = const(5)
# Standby settings in ms
BMP280_STANDBY_0_5 = const(0)
BMP280_STANDBY_62_5 = const(1)
BMP280_STANDBY_125 = const(2)
BMP280_STANDBY_250 = const(3)
BMP280_STANDBY_500 = const(4)
BMP280_STANDBY_1000 = const(5)
BMP280_STANDBY_2000 = const(6)
BMP280_STANDBY_4000 = const(7)
# IIR Filter setting
BMP280_IIR_FILTER_OFF = const(0)
BMP280_IIR_FILTER_2 = const(1)
BMP280_IIR_FILTER_4 = const(2)
BMP280_IIR_FILTER_8 = const(3)
BMP280_IIR_FILTER_16 = const(4)
# Oversampling setting
BMP280_OS_ULTRALOW = const(0)
BMP280_OS_LOW = const(1)
BMP280_OS_STANDARD = const(2)
BMP280_OS_HIGH = const(3)
BMP280_OS_ULTRAHIGH = const(4)
# Oversampling matrix
# (PRESS_OS, TEMP_OS, sample time in ms)
_BMP280_OS_MATRIX = [
[BMP280_PRES_OS_1, BMP280_TEMP_OS_1, 7],
[BMP280_PRES_OS_2, BMP280_TEMP_OS_1, 9],
[BMP280_PRES_OS_4, BMP280_TEMP_OS_1, 14],
[BMP280_PRES_OS_8, BMP280_TEMP_OS_1, 23],
[BMP280_PRES_OS_16, BMP280_TEMP_OS_2, 44]
]
# Use cases
BMP280_CASE_HANDHELD_LOW = const(0)
BMP280_CASE_HANDHELD_DYN = const(1)
BMP280_CASE_WEATHER = const(2)
BMP280_CASE_FLOOR = const(3)
BMP280_CASE_DROP = const(4)
BMP280_CASE_INDOOR = const(5)
_BMP280_CASE_MATRIX = [
[BMP280_POWER_NORMAL, BMP280_OS_ULTRAHIGH, BMP280_IIR_FILTER_4, BMP280_STANDBY_62_5],
[BMP280_POWER_NORMAL, BMP280_OS_STANDARD, BMP280_IIR_FILTER_16, BMP280_STANDBY_0_5],
[BMP280_POWER_FORCED, BMP280_OS_ULTRALOW, BMP280_IIR_FILTER_OFF, BMP280_STANDBY_0_5],
[BMP280_POWER_NORMAL, BMP280_OS_STANDARD, BMP280_IIR_FILTER_4, BMP280_STANDBY_125],
[BMP280_POWER_NORMAL, BMP280_OS_LOW, BMP280_IIR_FILTER_OFF, BMP280_STANDBY_0_5],
[BMP280_POWER_NORMAL, BMP280_OS_ULTRAHIGH, BMP280_IIR_FILTER_16, BMP280_STANDBY_0_5]
]
_BMP280_REGISTER_ID = const(0xD0)
_BMP280_REGISTER_RESET = const(0xE0)
_BMP280_REGISTER_STATUS = const(0xF3)
_BMP280_REGISTER_CONTROL = const(0xF4)
_BMP280_REGISTER_CONFIG = const(0xF5) # IIR filter config
_BMP280_REGISTER_DATA = const(0xF7)
class BMP280:
def __init__(self, i2c_bus, addr=0x76, use_case=BMP280_CASE_HANDHELD_DYN):
self._bmp_i2c = i2c_bus
self._i2c_addr = addr
# read calibration data
# < little-endian
# H unsigned short
# h signed short
self._T1 = unp('<H', self._read(0x88, 2))[0]
self._T2 = unp('<h', self._read(0x8A, 2))[0]
self._T3 = unp('<h', self._read(0x8C, 2))[0]
self._P1 = unp('<H', self._read(0x8E, 2))[0]
self._P2 = unp('<h', self._read(0x90, 2))[0]
self._P3 = unp('<h', self._read(0x92, 2))[0]
self._P4 = unp('<h', self._read(0x94, 2))[0]
self._P5 = unp('<h', self._read(0x96, 2))[0]
self._P6 = unp('<h', self._read(0x98, 2))[0]
self._P7 = unp('<h', self._read(0x9A, 2))[0]
self._P8 = unp('<h', self._read(0x9C, 2))[0]
self._P9 = unp('<h', self._read(0x9E, 2))[0]
# output raw
self._t_raw = 0
self._t_fine = 0
self._t = 0
self._p_raw = 0
self._p = 0
self.read_wait_ms = 0 # interval between forced measure and readout
self._new_read_ms = 200 # interval between
self._last_read_ts = 0
if use_case is None:
self.use_case(use_case)
def _read(self, addr, size=1):
return self._bmp_i2c.readfrom_mem(self._i2c_addr, addr, size)
def _write(self, addr, b_arr):
if not type(b_arr) is bytearray:
b_arr = bytearray([b_arr])
return self._bmp_i2c.writeto_mem(self._i2c_addr, addr, b_arr)
def _gauge(self):
# TODO limit new reads
# read all data at once (as by spec)
d = self._read(_BMP280_REGISTER_DATA, 6)
self._p_raw = (d[0] << 12) + (d[1] << 4) + (d[2] >> 4)
self._t_raw = (d[3] << 12) + (d[4] << 4) + (d[5] >> 4)
self._t_fine = 0
self._t = 0
self._p = 0
def reset(self):
self._write(_BMP280_REGISTER_RESET, 0xB6)
def load_test_calibration(self):
self._T1 = 27504
self._T2 = 26435
self._T3 = -1000
self._P1 = 36477
self._P2 = -10685
self._P3 = 3024
self._P4 = 2855
self._P5 = 140
self._P6 = -7
self._P7 = 15500
self._P8 = -14600
self._P9 = 6000
def load_test_data(self):
self._t_raw = 519888
self._p_raw = 415148
def print_calibration(self):
print("T1: {} {}".format(self._T1, type(self._T1)))
print("T2: {} {}".format(self._T2, type(self._T2)))
print("T3: {} {}".format(self._T3, type(self._T3)))
print("P1: {} {}".format(self._P1, type(self._P1)))
print("P2: {} {}".format(self._P2, type(self._P2)))
print("P3: {} {}".format(self._P3, type(self._P3)))
print("P4: {} {}".format(self._P4, type(self._P4)))
print("P5: {} {}".format(self._P5, type(self._P5)))
print("P6: {} {}".format(self._P6, type(self._P6)))
print("P7: {} {}".format(self._P7, type(self._P7)))
print("P8: {} {}".format(self._P8, type(self._P8)))
print("P9: {} {}".format(self._P9, type(self._P9)))
def _calc_t_fine(self):
# From datasheet page 22
self._gauge()
if self._t_fine == 0:
var1 = (((self._t_raw >> 3) - (self._T1 << 1)) * self._T2) >> 11
var2 = (((((self._t_raw >> 4) - self._T1)
* ((self._t_raw >> 4)
- self._T1)) >> 12)
* self._T3) >> 14
self._t_fine = var1 + var2
@property
def temperature(self):
self._calc_t_fine()
if self._t == 0:
self._t = ((self._t_fine * 5 + 128) >> 8) / 100.
return self._t
@property
def pressure(self):
# From datasheet page 22
self._calc_t_fine()
if self._p == 0:
var1 = self._t_fine - 128000
var2 = var1 * var1 * self._P6
var2 = var2 + ((var1 * self._P5) << 17)
var2 = var2 + (self._P4 << 35)
var1 = ((var1 * var1 * self._P3) >> 8) + ((var1 * self._P2) << 12)
var1 = (((1 << 47) + var1) * self._P1) >> 33
if var1 == 0:
return 0
p = 1048576 - self._p_raw
p = int((((p << 31) - var2) * 3125) / var1)
var1 = (self._P9 * (p >> 13) * (p >> 13)) >> 25
var2 = (self._P8 * p) >> 19
p = ((p + var1 + var2) >> 8) + (self._P7 << 4)
self._p = p / 256.0
return self._p
def _write_bits(self, address, value, length, shift=0):
d = self._read(address)[0]
m = int('1' * length, 2) << shift
d &= ~m
d |= m & value << shift
self._write(address, d)
def _read_bits(self, address, length, shift=0):
d = self._read(address)[0]
return d >> shift & int('1' * length, 2)
@property
def standby(self):
return self._read_bits(_BMP280_REGISTER_CONFIG, 3, 5)
@standby.setter
def standby(self, v):
assert 0 <= v <= 7
self._write_bits(_BMP280_REGISTER_CONFIG, v, 3, 5)
@property
def iir(self):
return self._read_bits(_BMP280_REGISTER_CONFIG, 3, 2)
@iir.setter
def iir(self, v):
assert 0 <= v <= 4
self._write_bits(_BMP280_REGISTER_CONFIG, v, 3, 2)
@property
def spi3w(self):
return self._read_bits(_BMP280_REGISTER_CONFIG, 1)
@spi3w.setter
def spi3w(self, v):
assert v in (0, 1)
self._write_bits(_BMP280_REGISTER_CONFIG, v, 1)
@property
def temp_os(self):
return self._read_bits(_BMP280_REGISTER_CONTROL, 3, 5)
@temp_os.setter
def temp_os(self, v):
assert 0 <= v <= 5
self._write_bits(_BMP280_REGISTER_CONTROL, v, 3, 5)
@property
def press_os(self):
return self._read_bits(_BMP280_REGISTER_CONTROL, 3, 2)
@press_os.setter
def press_os(self, v):
assert 0 <= v <= 5
self._write_bits(_BMP280_REGISTER_CONTROL, v, 3, 2)
@property
def power_mode(self):
return self._read_bits(_BMP280_REGISTER_CONTROL, 2)
@power_mode.setter
def power_mode(self, v):
assert 0 <= v <= 3
self._write_bits(_BMP280_REGISTER_CONTROL, v, 2)
@property
def is_measuring(self):
return bool(self._read_bits(_BMP280_REGISTER_STATUS, 1, 3))
@property
def is_updating(self):
return bool(self._read_bits(_BMP280_REGISTER_STATUS, 1))
@property
def chip_id(self):
return self._read(_BMP280_REGISTER_ID, 2)
@property
def in_normal_mode(self):
return self.power_mode == BMP280_POWER_NORMAL
def force_measure(self):
self.power_mode = BMP280_POWER_FORCED
def normal_measure(self):
self.power_mode = BMP280_POWER_NORMAL
def sleep(self):
self.power_mode = BMP280_POWER_SLEEP
def use_case(self, uc):
assert 0 <= uc <= 5
pm, oss, iir, sb = _BMP280_CASE_MATRIX[uc]
t_os, p_os, self.read_wait_ms = _BMP280_OS_MATRIX[oss]
self._write(_BMP280_REGISTER_CONFIG, (iir << 2) + (sb << 5))
self._write(_BMP280_REGISTER_CONTROL, pm + (p_os << 2) + (t_os << 5))
def oversample(self, oss):
assert 0 <= oss <= 4
t_os, p_os, self.read_wait_ms = _BMP280_OS_MATRIX[oss]
self._write_bits(_BMP280_REGISTER_CONTROL, p_os + (t_os << 3), 2)