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Original file line number | Diff line number | Diff line change |
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------------------------------------------------------------------------------ | ||
-- BMP085 query module | ||
-- | ||
-- LICENCE: http://opensource.org/licenses/MIT | ||
-- Vladimir Dronnikov <dronnikov@gmail.com> | ||
-- Heavily based on work of Christee <Christee@nodemcu.com> | ||
-- | ||
-- Example: | ||
-- require("bmp085").read(sda, scl) | ||
------------------------------------------------------------------------------ | ||
local M | ||
do | ||
-- cache | ||
local i2c, tmr = i2c, tmr | ||
-- helpers | ||
local r8 = function(reg) | ||
i2c.start(0) | ||
i2c.address(0, 0x77, i2c.TRANSMITTER) | ||
i2c.write(0, reg) | ||
i2c.stop(0) | ||
i2c.start(0) | ||
i2c.address(0, 0x77, i2c.RECEIVER) | ||
local r = i2c.read(0, 1) | ||
i2c.stop(0) | ||
return r:byte(1) | ||
end | ||
local w8 = function(reg, val) | ||
i2c.start(0) | ||
i2c.address(0, 0x77, i2c.TRANSMITTER) | ||
i2c.write(0, reg) | ||
i2c.write(0, val) | ||
i2c.stop(0) | ||
end | ||
local r16u = function(reg) | ||
return r8(reg) * 256 + r8(reg + 1) | ||
end | ||
local r16 = function(reg) | ||
local r = r16u(reg) | ||
if r > 32767 then r = r - 65536 end | ||
return r | ||
end | ||
-- calibration data | ||
local AC1, AC2, AC3, AC4, AC5, AC6, B1, B2, MB, MC, MD | ||
-- read | ||
local read = function(sda, scl, oss) | ||
i2c.setup(0, sda, scl, i2c.SLOW) | ||
-- cache calibration data | ||
if not AC1 then | ||
AC1 = r16(0xAA) | ||
AC2 = r16(0xAC) | ||
AC3 = r16(0xAE) | ||
AC4 = r16u(0xB0) | ||
AC5 = r16u(0xB2) | ||
AC6 = r16u(0xB4) | ||
B1 = r16(0xB6) | ||
B2 = r16(0xB8) | ||
MB = r16(0xBA) | ||
MC = r16(0xBC) | ||
MD = r16(0xBE) | ||
end | ||
-- get raw P | ||
local p | ||
-- NB: optimize for oss = 0 | ||
if not oss then oss = 0 end | ||
if oss == 0 then | ||
oss = 0 | ||
w8(0xF4, 0x34) | ||
tmr.delay(5000) | ||
p = r8(0xF6) * 256 + r8(0xF7) | ||
else | ||
w8(0xF4, 0x34 + 64 * oss) | ||
tmr.delay(30000) | ||
p = r8(0xF6) * 65536 + r8(0xF7) * 256 + r8(0xF8) | ||
p = p / 2^(8 - oss) | ||
end | ||
-- get T | ||
w8(0xF4, 0x2E) | ||
tmr.delay(5000) | ||
local t = r16(0xF6) | ||
local X1 = (t - AC6) * AC5 / 32768 | ||
local X2 = MC * 2048 / (X1 + MD) | ||
t = (X2 + X1 + 8) / 16 | ||
-- normalize P | ||
local B5 = t * 16 - 8; | ||
local B6 = B5 - 4000 | ||
local X1 = B2 * (B6 * B6 / 4096) / 2048 | ||
local X2 = AC2 * B6 / 2048 | ||
local X3 = X1 + X2 | ||
local B3 = ((AC1 * 4 + X3) * 2^oss + 2) / 4 | ||
X1 = AC3 * B6 / 8192 | ||
X2 = (B1 * (B6 * B6 / 4096)) / 65536 | ||
X3 = (X1 + X2 + 2) / 4 | ||
local B4 = AC4 * (X3 + 32768) / 32768 | ||
local B7 = (p - B3) * (50000 / 2^oss) | ||
p = B7 / B4 * 2 | ||
X1 = (p / 256)^2 | ||
X1 = (X1 * 3038) / 65536 | ||
X2 = (-7357 * p) / 65536 | ||
p = p + (X1 + X2 + 3791) / 16 | ||
-- Celsius * 10, Hg mm * 10 | ||
return t, p * 3 / 40 | ||
end | ||
-- expose | ||
M = { | ||
read = read, | ||
} | ||
end | ||
return M |
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