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@jvalrog
Created May 11, 2018
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BME280 Linux library for Ruby
=begin
Copyright 2018 Javier Valencia
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
3. Neither the name of the copyright holder nor the names of its contributors
may be used to endorse or promote products derived from this software
without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
THE POSSIBILITY OF SUCH DAMAGE.
=end
require_relative "i2cdev"
class BME280 < I2CDev
R_DIG_T1 = 0x88
R_DIG_P1 = 0x8E
R_DIG_H1 = 0xA1
R_DIG_H2 = 0xE1
R_PRESS_MSB = 0xF7
R_CTRL_HUM = 0xF2
R_CTRL_MEAS = 0xF4
def self.base_address
0x76
end
def initialize(*params)
super(*params)
@sensors = {}
setup
end
def update
adc = adc_read
t_fine = calc_t_fine(adc[:t])
@sensors[:t] = compensate_t(t_fine)
@sensors[:p] = compensate_p(adc[:p], t_fine)
@sensors[:h] = compensate_h(adc[:h], t_fine)
end
def temperature
update if @sensors.empty?
@sensors[:t].round(2)
end
def pressure
update if @sensors.empty?
@sensors[:p].round(2)
end
def humidity
update if @sensors.empty?
@sensors[:h].round(2)
end
private
def setup
i2c_write(R_CTRL_HUM, 0x05)
i2c_write(R_CTRL_MEAS, 0xb7)
end
def calib
return @cdata if defined?(@cdata)
t_data = i2c_read(R_DIG_T1, 6)
p_data = i2c_read(R_DIG_P1, 18)
h_data = ""
h_data << i2c_read(R_DIG_H1, 1)
h_data << i2c_read(R_DIG_H2, 7)
h_data = patch_h_data(h_data)
@cdata = {t: t_data.unpack("S<s<2"), p: p_data.unpack("S<s<8"), h: h_data.unpack("Cs<Cs<2c")}
end
def patch_h_data(h_data)
bytes = h_data.bytes
e5 = bytes[5]
h4 = (bytes[4] << 4) + (e5 & 0x0f)
bytes[4] = h4 & 0xff
bytes[5] = h4 >> 8
h5 = (e5 >> 4) + (bytes[6] << 4)
bytes.insert(6, h5 & 0xff)
bytes[7] = h5 >> 8
bytes.pack("C*")
end
def adc_read
data = i2c_read(R_PRESS_MSB, 8)
data = patch_adc_data(data)
p, t, h = data.unpack("L>L>S>")
{p: p >> 12, t: t >> 12, h: h}
end
def patch_adc_data(adc_data)
bytes = adc_data.bytes
bytes.insert(3, 0)
bytes.insert(7, 0)
bytes.pack("C*")
end
def calc_t_fine(adc_t)
var1 = (adc_t / 16384.0 - calib[:t][0] / 1024.0) * calib[:t][1]
var2 = ((adc_t / 131072.0 - calib[:t][0] / 8192) ** 2) * calib[:t][2]
var1 + var2
end
def compensate_t(t_fine)
t_fine / 5120.0
end
def compensate_p(adc_p, t_fine)
var1 = t_fine / 2.0 - 64000.0
var2 = (var1 ** 2) * calib[:p][5] / 32768.0
var2 = var2 + var1 * calib[:p][4] * 2.0
var2 = var2 / 4.0 + calib[:p][3] * 65536.0
var1 = (calib[:p][2] * (var1 ** 2) / 524288.0 + calib[:p][1] * var1) / 524288.0
var1 = (1.0 + var1 / 32768.0) * calib[:p][0]
return 0 if var1 == 0
p = 1048576.0 - adc_p
p = (p - var2 / 4096.0) * 6250.0 / var1
var1 = calib[:p][8] * (p ** 2) / 2147483648.0
var2 = p * calib[:p][7] / 32768.0
(p + (var1 + var2 + calib[:p][6]) / 16.0) / 100.0
end
def compensate_h(adc_h, t_fine)
var = t_fine - 76800.0
return 0 if var.zero?
var = (adc_h - (calib[:h][3] * 64.0 + calib[:h][4] / 16384.0 * var)) *
(calib[:h][1] / 65536.0 * (1.0 + calib[:h][5] / 67108864.0 * var *
(1.0 + calib[:h][2] / 67108864.0 * var)))
var = var * (1.0 - calib[:h][0] * var / 524288.0)
if var > 100.0
var = 100.0
elsif var < 0.0
var = 0.0
end
var
end
end
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