forked from nodemcu/nodemcu-firmware
-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathyet-another-bmp085.lua
101 lines (101 loc) · 2.55 KB
/
yet-another-bmp085.lua
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
------------------------------------------------------------------------------
-- BMP085 query module
--
-- LICENCE: http://opensource.org/licenses/MIT
-- Vladimir Dronnikov <[email protected]>
-- Heavily based on work of Christee <[email protected]>
--
-- Example:
-- dofile("bmp085.lua").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
if not oss then oss = 0 end
if oss <= 0 then oss = 0 end
if oss > 3 then oss = 3 end
w8(0xF4, 0x34 + 64 * oss)
tmr.delay((4 + 3 ^ oss) * 1000)
local p = r8(0xF6) * 65536 + r8(0xF7) * 256 + r8(0xF8)
p = p / 2 ^ (8 - oss)
-- 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