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