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Update set_environmental_data function. #26

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Merged
merged 1 commit into from
Dec 13, 2018
Merged

Update set_environmental_data function. #26

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16 changes: 6 additions & 10 deletions adafruit_ccs811.py
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@
"""
import time
import math
import struct

from micropython import const
from adafruit_bus_device.i2c_device import I2CDevice
Expand Down Expand Up @@ -192,21 +193,16 @@ def set_environmental_data(self, humidity, temperature):
# Humidity is stored as an unsigned 16 bits in 1/512%RH. The default
# value is 50% = 0x64, 0x00. As an example 48.5% humidity would be 0x61,
# 0x00.
hum_perc = int(humidity) << 1
humidity = int(humidity * 512)

# Temperature is stored as an unsigned 16 bits integer in 1/512 degrees
# there is an offset: 0 maps to -25C. The default value is 25C = 0x64,
# 0x00. As an example 23.5% temperature would be 0x61, 0x00.
parts = math.fmod(temperature)
fractional = parts[0]
temperature = parts[1]
temperature = int((temperature + 25) * 512)

temp_high = ((temperature + 25) << 9)
temp_low = ((fractional / 0.001953125) & 0x1FF)

temp_conv = (temp_high | temp_low)

buf = bytearray([_ENV_DATA, hum_perc, 0x00, ((temp_conv >> 8) & 0xFF), (temp_conv & 0xFF)])
buf = bytearray(5)
buf[0] = _ENV_DATA
struct.pack_into(">HH", buf, 1, humidity, temperature)

with self.i2c_device as i2c:
i2c.write(buf)
Expand Down