lua code for getting data from bmp085
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Christee@nodemcu.com
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99a2001225
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-- BMP085 I2C module for NODEMCU
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-- NODEMCU TEAM
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-- LICENCE: http://opensource.org/licenses/MIT
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-- Christee <Christee@nodemcu.com>
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--------------------------------------------------------------------------------
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local moduleName = ...
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local M = {}
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_G[moduleName] = M
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--default value for i2c communication
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local id=0
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--default oversampling setting
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local oss = 0
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--CO: calibration coefficients table.
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local CO = {}
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-- read reg for 1 byte
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local function read_reg(dev_addr, reg_addr)
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i2c.start(id)
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i2c.address(id, dev_addr ,i2c.TRANSMITTER)
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i2c.write(id,reg_addr)
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i2c.stop(id)
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i2c.start(id)
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i2c.address(id, dev_addr,i2c.RECEIVER)
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local c=i2c.read(id,1)
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i2c.stop(id)
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return c
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end
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--write reg for 1 byte
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local function write_reg(dev_addr, reg_addr, reg_val)
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i2c.start(id)
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i2c.address(id, dev_addr, i2c.TRANSMITTER)
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i2c.write(id, reg_addr)
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i2c.write(id, reg_val)
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i2c.stop(id)
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end
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--get signed or unsigned 16
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--parameters:
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--reg_addr: start address of short
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--signed: if true, return signed16
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local function getShort(reg_addr, signed)
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local tH = string.byte(read_reg(0x77, reg_addr))
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local tL = string.byte(read_reg(0x77, (reg_addr + 1)))
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local temp = tH*256 + tL
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if (temp > 32767) and (signed == true) then
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temp = temp - 65536
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end
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return temp
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end
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-- initialize i2c
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--parameters:
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--d: sda
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--l: scl
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function M.init(d, l)
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if (d ~= nil) and (l ~= nil) and (d >= 0) and (d <= 11) and (l >= 0) and ( l <= 11) and (d ~= l) then
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sda = d
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scl = l
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else
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print("iic config failed!") return nil
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end
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print("init done")
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i2c.setup(id, sda, scl, i2c.SLOW)
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--get calibration coefficients.
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CO.AC1 = getShort(0xAA, true)
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CO.AC2 = getShort(0xAC, true)
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CO.AC3 = getShort(0xAE, true)
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CO.AC4 = getShort(0xB0)
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CO.AC5 = getShort(0xB2)
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CO.AC6 = getShort(0xB4)
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CO.B1 = getShort(0xB6, true)
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CO.B2 = getShort(0xB8, true)
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CO.MB = getShort(0xBA, true)
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CO.MC = getShort(0xBC, true)
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CO.MD = getShort(0xBE, true)
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end
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--get temperature from bmp085
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--parameters:
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--num_10x: bool value, if true, return number of 0.1 centi-degree
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-- default value is false, which return a string , eg: 16.7
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function M.getUT(num_10x)
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write_reg(0x77, 0xF4, 0x2E);
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tmr.delay(10000);
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local temp = getShort(0xF6)
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local X1 = (temp - CO.AC6) * CO.AC5 / 32768
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local X2 = CO.MC * 2048/(X1 + CO.MD)
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local r = (X2 + X1 + 8)/16
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if(num_10x == true) then
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return r
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else
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return ((r/10).."."..(r%10))
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end
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end
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--get raw data of pressure from bmp085
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--parameters:
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--oss: over sampling setting, which is 0,1,2,3. Default value is 0
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function M.getUP_raw(oss)
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local os = 0
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if ((oss == 0) or (oss == 1) or (oss == 2) or (oss == 3)) and (oss ~= nil) then
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os = oss
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end
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local ov = os * 64
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write_reg(0x77, 0xF4, (0x34 + ov));
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tmr.delay(30000);
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--delay 30ms, according to bmp085 document, wait time are:
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-- 4.5ms 7.5ms 13.5ms 25.5ms respectively according to oss 0,1,2,3
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local MSB = string.byte(read_reg(0x77, 0xF6))
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local LSB = string.byte(read_reg(0x77, 0xF7))
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local XLSB = string.byte(read_reg(0x77, 0xF8))
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local up_raw = (MSB*65536 + LSB *256 + XLSB)/2^(8 - os)
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return up_raw
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end
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--get calibrated data of pressure from bmp085
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--parameters:
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--oss: over sampling setting, which is 0,1,2,3. Default value is 0
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function M.getUP(oss)
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local os = 0
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if ((oss == 0) or (oss == 1) or (oss == 2) or (oss == 3)) and (oss ~= nil) then
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os = oss
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end
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local raw = M.getUP_raw(os)
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local B5 = M.getUT(true) * 16 - 8;
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local B6 = B5 - 4000
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local X1 = CO.B2 * (B6 * B6 /4096)/2048
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local X2 = CO.AC2 * B6 / 2048
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local X3 = X1 + X2
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local B3 = ((CO.AC1*4 + X3)*2^os + 2)/4
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X1 = CO.AC3 * B6 /8192
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X2 = (CO.B1 * (B6 * B6 / 4096))/65536
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X3 = (X1 + X2 + 2)/4
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local B4 = CO.AC4 * (X3 + 32768) / 32768
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local B7 = (raw -B3) * (50000/2^os)
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local p = B7/B4 * 2
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X1 = (p/256)^2
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X1 = (X1 *3038)/65536
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X2 = (-7357 *p)/65536
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p = p +(X1 + X2 + 3791)/16
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return p
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end
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--get estimated data of altitude from bmp085
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--parameters:
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--oss: over sampling setting, which is 0,1,2,3. Default value is 0
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function M.getAL(oss)
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--Altitudi can be calculated by pressure refer to sea level pressure, which is 101325
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--pressure changes 100pa corresponds to 8.43m at sea level
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return (M.getUP(oss) - 101325)*843/10000
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end
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return M
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