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Ligne 182 : − + − − So I have fixed the baseline as follow before reading the altitude: − Serial.print(bme.readAltitude(1002.00)); + − Serial.println(" m"); + Ligne 206 :
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ENG-CANSAT-PICO-BMP280 (voir la source)
Version du 26 février 2022 à 23:57
, 26 février 2022 à 23:57→Testing the sensor
<syntaxhighlight lang="python">
<syntaxhighlight lang="python">
# Read the sensor values:
# (temperature_celcius, pressure_hpa, humidity_percent)
# Humidity only applies to BME280 only, not BMP280.
#
from machine import I2C
from machine import I2C
# BME280 aslo work for BMP280
# BME280 aslo work for BMP280
Which produce the following results:
Which produce the following results:
<nowiki>(22.28, 1017.68, 0.0)
<syntaxhighlight lang="bash">
(22.28, 1017.68, 0.0)
(22.27, 1017.66, 0.0)
(22.27, 1017.66, 0.0)
(21.87, 1017.67, 0.0)
(21.87, 1017.67, 0.0)
(21.83, 1017.68, 0.0)
(21.83, 1017.68, 0.0)
(21.81, 1017.68, 0.0)
(21.81, 1017.68, 0.0)
(21.81, 1017.68, 0.0)
(21.81, 1017.68, 0.0)</nowiki>
</syntaxhighlight>
By activating the Plotter, the value can even be made visible as a graph. However, to see a proper graph evolution, the best is to replace the {{fname|sleep(1)}} to {{fname|sleep( 60*30 )}} (30 min).
By activating the Plotter, the value can even be made visible as a graph. However, to see a proper graph evolution, the best is to replace the {{fname|sleep(1)}} to {{fname|sleep( 60*30 )}} (30 min).
<syntaxhighlight lang="python">
<syntaxhighlight lang="python">
# Read Local pressure then
# Calculate corresponding Altitude
#
from machine import I2C
from machine import I2C
# BME280 aslo work for BMP280
# BME280 aslo work for BMP280
from bme280 import BME280, BMP280_I2CADDR
from bme280 import BME280, BMP280_I2CADDR
from time import sleep
from time import sleep
i2c = I2C(1)
i2c = I2C(0)
baseline = 1032.0 # day's pressure at sea level
baseline = 1032.0 # day's pressure at sea level
By example, today the pressure is 1002.00 hPa at the Belgian's sea level.
By example, today the pressure is 1002.00 hPa at the Belgian's sea level.
<font color="red">this value is critical if you want to evaluate the altitude of the sensor.</font>. It is also important to know the current altitude if you plan to calculate the "correction" for the normalized SLP pressure.
<font color="red">this value is critical if you want to evaluate the altitude of the sensor</font>.
It is also important to know the current altitude if you plan to calculate the "correction" for the normalized SLP pressure.
{{underline|Remark:}}<br />
It is quite easy to know the current sea level pressure by using an Internet Weather Broadcast like [http://www.meteobelgique.be/observations/temps-reel/stations-meteo.html this link to meteobelgique.be]
It is quite easy to know the current sea level pressure by using an Internet Weather Broadcast like [http://www.meteobelgique.be/observations/temps-reel/stations-meteo.html this link to meteobelgique.be]
{{underline|First:}} You must know your altitude (121m in my case, see here before How I did calculate it).
{{underline|First:}} You must know your altitude (121m in my case, see here before How I did calculate it).
{{underline|Then:}} Read the pressure and apply a correction factor.
{{underline|Then:}} Read the pressure and apply the SLP correction factor.
<syntaxhighlight lang="python">
<syntaxhighlight lang="python">
# Read Local pressure
# Calculate corresponding SLP pressure
# (SLP: sea level pressure)
#
from machine import I2C
# BME280 aslo work for BMP280
from bme280 import BME280, BMP280_I2CADDR
from time import sleep
i2c = I2C(0)
# Sensor altitude (in meter) required to
# calculate SLP (See Level Pressure)
altitude = 120.1
bmp = BME280( i2c=i2c, address=BMP280_I2CADDR )
while True:
# returns a tuple with (temperature, pressure_hPa, humidity)
p = bmp.raw_values[1]
p_sea = p + (altitude/8.3)
print( "Plocal: %6.1f hPa, Psea: %6.1f hPa" % (p,p_sea) )
sleep(1)
</syntaxhighlight>
</syntaxhighlight>
which returns:
<nowiki>Plocal: 1017.4 hPa, Psea: 1031.8 hPa
Plocal: 1017.4 hPa, Psea: 1031.9 hPa
Plocal: 1017.3 hPa, Psea: 1031.8 hPa
Plocal: 1017.4 hPa, Psea: 1031.8 hPa
Plocal: 1017.4 hPa, Psea: 1031.9 hPa
Plocal: 1017.4 hPa, Psea: 1031.9 hPa
Plocal: 1017.4 hPa, Psea: 1031.8 hPa</nowiki>
{{ENG-CANSAT-PICO-TRAILER}}
{{ENG-CANSAT-PICO-TRAILER}}