yet another bmp085 module added

2015-01-31 12:55:51 +03:00 · 2015-01-31 12:55:51 +03:00 · a00044980c
parent 169699b93a
commit a00044980c
1 changed files with 108 additions and 0 deletions
--- a/lua_examples/yet-another-bmp085.lua
+++ b/lua_examples/yet-another-bmp085.lua
@ -0,0 +1,108 @@
+------------------------------------------------------------------------------
+-- 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