[luatos sensor] 2 air pressure bmp180

1 Preface

Try to get BMP180 Parameters of .

2 Official source code

BMP180 Air pressure sensor ：https://doc.openluat.com/wiki/21?wiki_page_id=2729

Reference material ：BMP180 Detailed explanation and examples of air pressure sensor （STM32 With source code ）
This article is particularly well written .

In addition, you can also learn from arduino In order to get bmp180 drive , Change in contrast to .

3 Hardware

i2c The equipment is similar , The point is addr,BMP180 by 0x77.
BMP180 Only four pins , The picture above shows BH1750. Don't even addr

4 Official code problem

4.1 i2c.send The change of return value causes printing error log

My development board is esp32 Of , Should be bsp Changed , Therefore, the previous source code is not applicable .

The phenomenon ：log Tips i2c.send Returns an error
reason ： In the official example i2c,send() The return value is the number of data , Now the return value is true/false

4.2 math.pow Abandoning

math.pow stay lua5.3 Has been deprecated . Use the operator ^

    -- local altitude = 44330 * (1-math.pow(((p) / 101325.0),(1.0/5.255)))
    local altitude = 44330 * (1-((p) / 101325.0)^(1.0/5.255))
    -- math.pow  stay lua5.3 Has been deprecated . Use the operator ^

4.3 Common unit conversion

In the source code, multiply the temperature by 0.1, pressure /1000 Conversion for kPa, At an altitude of /1000 Conversion for m

5 Code

BMP180.lua

---  Module function ：I2C BMP180 A functional test .
-- @author denghai,youkai
-- @module i2c.BMP180
-- @license MIT
-- @copyright openLuat
-- @release 2021.09.22

--[[ BMP180_REG_ID = 0xD0, //contains 0x55 after power on BMP180_REG_RESET = 0xE0, //write 0xB6 to reset BMP180_REG_STATUS = 0xF3, //bit 0: im_update, bit 3: measuring BMP180_REG_CTRL_MEAS = 0xF4, //sets data acquisition options of device BMP180_REG_CONFIG = 0xF5, //sets the rate, filter and interface options of the device. BMP180_REG_OUT = 0xF6, //raw conversion results BMP180_REG_CAL_AC1 = 0xAA, //2 bytes each. can never be 0x0000 or oxFFFF BMP180_REG_CAL_AC2 = 0xAC, BMP180_REG_CAL_AC3 = 0xAE, BMP180_REG_CAL_AC4 = 0xB0, BMP180_REG_CAL_AC5 = 0xB2, BMP180_REG_CAL_AC6 = 0xB4, BMP180_REG_CAL_B1 = 0xB6, BMP180_REG_CAL_B2 = 0xB8, BMP180_REG_CAL_MB = 0xBA, BMP180_REG_CAL_MC = 0xBC, BMP180_REG_CAL_MD = 0xBE, ]]


BMP180_REG_ID = 0xD0			--contains 0x55 after power on
BMP180_REG_RESET = 0xE0		--write 0xB6 to reset
BMP180_REG_STATUS = 0xF3		--bit 0: im_update bit 3: measuring
BMP180_REG_CTRL_MEAS = 0xF4	--sets data acquisition options of device 
BMP180_REG_CONFIG = 0xF5		--sets the rate filter and interface options of the device.
BMP180_REG_OUT = 0xF6			--raw conversion results

BMP180_REG_CAL_AC1 = 0xAA		--2 bytes each. can never be 0x0000 or oxFFFF
BMP180_REG_CAL_AC2 = 0xAC
BMP180_REG_CAL_AC3 = 0xAE
BMP180_REG_CAL_AC4 = 0xB0
BMP180_REG_CAL_AC5 = 0xB2
BMP180_REG_CAL_AC6 = 0xB4

BMP180_REG_CAL_B1 = 0xB6
BMP180_REG_CAL_B2 = 0xB8

BMP180_REG_CAL_MB = 0xBA
BMP180_REG_CAL_MC = 0xBC
BMP180_REG_CAL_MD = 0xBE

BMP180_CMD_RESET = 0xB6

--register 0xD0
BMP180_MASK_ID = 0xFF

--register 0xE0
BMP180_MASK_RESET = 0xFF

--register 0xF4
BMP180_MASK_OSS = 0xC0
BMP180_MASK_SCO = 0x20
BMP180_MASK_MCTRL = 0x1F

BMP180_CMD_TEMP = 0x2E      --start temperature conversion
BMP180_CMD_PRESS = 0x34     --start pressure conversion

-- i2c ID
i2cid = 0

-- i2c  rate 
speed = 100000

BMP180_i2c_addr = 0x77


--  initialization 
function BMP180_init_i2c(address)
    if i2c.setup(i2cid, speed, -1, 1) ~= speed then
        log.error("i2c", "setup fail", addr)
        return
    end
    addr = address
    -- print("BMP180 addr:",addr)
end

--  Reading data 
function BMP180_send(...)
    sys.wait(10)
    -- print("addr",addr)
    if not addr then
        log.info("i2c", "addr err")
        return
    end
    local t = {
    ...}
    -- print("t",t[1],t[2])
    temp_t =  i2c.send(i2cid, addr, t)
    -- print("#t",#t)
    -- print("temp_t",temp_t)
    -- if temp_t ~= #t then --  Now? i2c.BMP180_send() The return value is true 了 , It's not a number 
    if temp_t ~= true then
        log.error("i2c", "BMP180_send fail", #t)
        return
    end
    return true
end

--  send data 
function BMP180_read(n)
    sys.wait(10)
    if not addr then
        log.info("i2c", "addr err")
        return "\x00"
    end
    val = i2c.recv(i2cid, addr, n)
    -- log.info("BMP180_read", val:toHex())
    if val and #val > 0 then return val end
    return "\x00"
end

--  Read short  value  
function BMP180_short(addr, n)
    -- print("addr",addr)
    BMP180_send(addr)      --  Just address ？
    -- print("BMP180_send addr")
    -- print("n",n)
    if n then
        f, val = pack.unpack(BMP180_read(2), ">H")
    else
        f, val = pack.unpack(BMP180_read(2), ">h")
    end
    
    -- log.info("val", f, val)
    return f and val or 0
end

function BMP180_init()
    BMP180_init_i2c(BMP180_i2c_addr)      --  Pass in i2c Address 0x77 = 119
    BMP180_send(BMP180_REG_ID)      --  Incoming address 0xD0,  register id
    local id = BMP180_read(1)
    -- print("bmp180 reg id ",id)
    if "U"~=id then 
        print("error id",id)
        sys.restart("error i2c id!")
        return
    end
    --  Reset 
    BMP180_send(BMP180_REG_RESET,BMP180_CMD_RESET)     -- 0xE0,0XB6

    -- https://blog.csdn.net/weixin_50622833/article/details/118611152
    AC1 = BMP180_short(BMP180_REG_CAL_AC1)  -- 0xAA --2 bytes each. can never be 0x0000 or oxFFFF
    AC2 = BMP180_short(BMP180_REG_CAL_AC2)  -- 0xAC
    AC3 = BMP180_short(BMP180_REG_CAL_AC3)  -- 0xAE
    AC4 = BMP180_short(BMP180_REG_CAL_AC4,true)    -- 0xB0
    AC5 = BMP180_short(BMP180_REG_CAL_AC5,true)    -- 0xB2
    AC6 = BMP180_short(BMP180_REG_CAL_AC6,true)    -- 0xB4
    B1  = BMP180_short(BMP180_REG_CAL_B1)  -- 0xB6
    B2  = BMP180_short(BMP180_REG_CAL_B2)  -- 0xB8
    MB  = BMP180_short(BMP180_REG_CAL_MB)  -- 0xBA
    MC  = BMP180_short(BMP180_REG_CAL_MC)  -- 0xBC
    MD  = BMP180_short(BMP180_REG_CAL_MD)  -- 0xBE 
end

function BMP180_get_temp_press()
    
    --  temperature  ℃
    BMP180_send(BMP180_REG_CTRL_MEAS,BMP180_CMD_TEMP)     --0xF4 Represent measurement ,0x2E Indicating temperature 
    sys.wait(1000)
    log.info(" temperature raw", BMP180_short(BMP180_REG_OUT))        --0xF6 Data output 
    UT = BMP180_short(BMP180_REG_OUT)                  --  Temperature value 
    -- print("UT",UT)
    --  pressure  Pa
    BMP180_send(BMP180_REG_CTRL_MEAS,BMP180_CMD_PRESS)     --0xF4,0x34
    sys.wait(1000)
    BMP180_send(BMP180_REG_OUT)
    _, UP = pack.unpack(BMP180_read(2), "<H")          --  Barometric value 
    -- print("UP",UP)
    log.info(" pressure raw", UP)
    return BMP_UncompemstatedToTrue(UT,UP)

end

function BMP180_test()
    -- sys.wait(8000)

    BMP180_init()

    while true do
        sys.wait(2000)

        BMP180_get_temp_press()
    end

end


--https://blog.csdn.net/weixin_50622833/article/details/118611152

--// Use the obtained parameters to correct the temperature and atmospheric pressure , And calculate the altitude 
function BMP_UncompemstatedToTrue(UT,UP)
    local Press = 0
    local X1 = (UT - AC6) * AC5/32768       -- 2^15, Data shift right 15 position 
    -- log.info("X1 ",X1,"UT ",UT,"AC6 ",AC6)
    -- local X2 = bit.lshift(MC,11) / (X1 + MD)
    local X2 = MC*2048 / (X1 + MD)          -- 2^11, Move left 11 position 
    -- log.info("X2",MC,"MC",X2,"MD",MD)
    local B5 = X1 + X2
    -- log.info("B5",B5)
    -- local Temp = bit.rshift((B5 + 8) ,4)
    local Temp  = (B5 + 8)/16
    Temp = Temp * 0.1
    log.info(" temperature : ",Temp.." °C")

    local B6 = B5 - 4000
    -- log.info("B6",B6)
    X1 = (B2 *((B6 * B6)/4096))/2048
    -- X1 = bit.rshift(B2 * bit.rshift(B6 * B6,12) ,11)
    -- log.info("X1",X1,"B2",B2,"B6",B6)
    X2 = (AC2 * B6)/2048
    -- X2 = bit.rshift(AC2 * B6,11)
    -- log.info("X2",X2,"AC2",AC2)
    local X3 = X1 + X2
    -- log.info("X3",X3)
    local B3 = ((AC1 * 4 + X3) + 2) /4
    -- log.info("B3",B3,"AC1",AC1)
    X1 = (AC3 * B6)/8192
    -- X1 = bit.rshift(AC3 * B6 ,13)
    -- log.info("X1",X1,"AC3",AC3)
    X2 = (B1 *((B6*B6)/4096)) /65536
    -- X2 = bit.rshift((B1 *bit.rshift(B6*B6 ,12)) ,16)
    -- log.info("X2",X2,"B1",B1)
    -- X3 = bit.rshift(X1 + X2 + 2, 2)
    X3 = (X1 + X2 + 2)/4
    -- log.info("X3",X3)
    local B4 = (AC4 * (X3 + 32768))/32768
    -- local B4 = bit.rshift(AC4 * (X3 + 32768) ,15)
    -- log.info("B4",B4,"AC4",AC4)
    local B7 = (UP - B3) * 50000
    -- log.info("B7",B7,"UP",UP)
    if(B7 < 0x80000000) then
        Press = (B7 * 2) / B4
    else
        Press = (B7 / B4) * 2
    end
    -- log.info("Press",Press)
    X1 = (Press/256) * (Press/256)
    -- X1 = bit.rshift(Press ,8) * bit.rshift(Press,8)
    -- log.info("X1",X1)
    X1 = (X1 * 3038)/65536
    -- X1 = bit.rshift(X1 * 3038,16)
    -- log.info("X1",X1)
    X2 = (-7357 * Press)/65536
    -- X2 = bit.rshift(-7357 * Press, 16)
    -- log.info("X2",X2)
    Press = Press + (X1 + X2 + 3791)/16
    -- Press = Press + bit.rshift(X1 + X2 + 3791,4)
    -- log.info(" Air pressure correction ", Press)
    -- Press = Press * 0.001
    log.info(" pressure : ", Press * 0.001 .." kPa")
    local altitude = 44330 * (1-((Press) / 101325.0)^1.0/5.255)
    altitude = altitude * 0.001
    log.info(" At an altitude of : ", altitude.." m")

    return Temp,Press * 0.001,altitude
end 

main.lua

PROJECT = "BMP180"
VERSION = "1.0.0"

_G.sys = require("sys")

--  load I²C Function test module 
require ("BMP180")

sys.taskInit(function()
    -- ps: Yes wait You can't put it outside 

    BMP180_test()
    -- sys.wait(1500)

    while 1 do
        

        sys.wait(100)
    end
end)

sys.run()

6 result

Personally, I feel that the accuracy is not high .