option explicit
option default none
'
' BME280 routines and test harness
'
const BME280_ADDRESS = &H77
const BME280_REGISTER_T1 = &H88
const BME280_REGISTER_P1 = &H8E
const BME280_REGISTER_H1 = &HA1
const BME280_REGISTER_H2 = &HE1
const BME280_REGISTER_CHIPID = &HD0
const BME280_REGISTER_CONTROLHUMID = &HF2
const BME280_REGISTER_CONTROL = &HF4
const BME280_REGISTER_PRESSUREDATA = &HF7
const BME280_REGISTER_TEMPDATA = &HFA
const BME280_REGISTER_HUMIDDATA = &HFD
'
dim integer s16=&HFFFFFFFFFFFF0000 , s16b=&H8000
dim integer s12=&HFFFFFFFFFFFFF000 , s12b=&H800
dim integer s8= &HFFFFFFFFFFFFFF00 , s8b=&H80
'
DIM INTEGER T1,T2,T3 'uint16_t, int16_t, int16_t
DIM INTEGER P1,P2,P3,P4,P5,P6,P7,P8,P9 'uint16_t, 8 x int16_t
DIM INTEGER H1,H2,H3,H4,H5,H6 'uint8_t, int16_t , uint8_t, int16_t, int16_t, int8_t
'
dim INTEGER t_fine 'used to store accurate temp reading from temp conversion for use in pressure and humidity conversions
'
' Test program
'
bme280_init
do
print bme280_read_temp() 'must be run before pressure or humidity
print bme280_read_pressure()
print bme280_read_humidity()
pause 2000
loop
'
end
'
'***************************************************************************************************
'
function bme280_read_temp() as float
local integer var1,var2,adc_T
local adc%(2)
i2c write BME280_ADDRESS,1,1,BME280_REGISTER_TEMPDATA
i2c read BME280_ADDRESS,0,3,adc%()
adc_T=((adc%(0)<<16) OR (adc%(1)<<8) or adc%(2))>>4
var1 = ((((adc_T>>3) - (T1 <<1))) * T2) \ q(11)
var2 = (((((adc_T>>4) - (T1)) * ((adc_T\ q(4)) - (T1))) \ q(12)) * (T3)) \ q(14)
t_fine = var1 + var2
bme280_read_temp = ((t_fine * 5 + 128) \ q(8))/100.0
end function

function bme280_read_pressure() as float
local integer var1, var2, adc_P, p
local adc%(2)
i2c write BME280_ADDRESS,1,1,BME280_REGISTER_PRESSUREDATA
i2c read BME280_ADDRESS,0,3,adc%()
adc_P=((adc%(0)<<16) OR (adc%(1)<<8) or adc%(2))>>4
var1 = t_fine - 128000
var2 = var1 * var1 * P6
var2 = var2 + ((var1 * P5)<<17)
var2 = var2 + (P4 << 35)
var1 = ((var1 * var1 * P3)\ q(8)) + ((var1 * P2)<<12)
var1 = ((1<<47)+var1)*P1\ q(33)
if var1 = 0 THEN
bme280_read_pressure = 0' avoid exception caused by division by zero
exit function
endif
p = 1048576 - adc_P
p = (((p<<31) - var2)*3125) \ var1
var1 = (P9 * (p\ q(13)) * (p\ q(13))) \ q(25)
var2 = (P8 * p) \ q(19)
p = ((p + var1 + var2) \ q(8)) + (P7<<4)
bme280_read_pressure = p/25600.0
end function
'
function bme280_read_humidity() as float
local integer v_x1,adc_H
local adc%(1)
i2c write BME280_ADDRESS,1,1,BME280_REGISTER_HUMIDDATA
i2c read BME280_ADDRESS,0,2,adc%()
adc_H=(adc%(0)<<8) or adc%(1)
v_x1 = t_fine - 76800
v_x1=(((((adc_H<<14)-((H4)<<20)-(H5*v_x1))+16384)\ q(15))*(((((((v_x1*H6)\ q(10))*(((v_x1*H3)\ q(11))+32768))\ q(10))+2097152)*H2+8192)\ q(14)))
v_x1 = (v_x1 - (((((v_x1 \ q(15)) * (v_x1 \ q(15))) \ q(7)) * (H1)) \ q(4)))
if v_x1< 0 then v_x1 = 0
if v_x1 > 419430400 then v_x1= 419430400
bme280_read_humidity = (v_x1\ q(12)) / 1024.0
end function

sub bme280_init
local i%,cal%(17)
i2c open 400,1000 '400KHz bus speed
i2c write BME280_ADDRESS,1,1,BME280_REGISTER_CHIPID
i2c read BME280_ADDRESS,0,1,i%
if i%<>&H60 then print "Error BME280 not found"
'
i2c write BME280_ADDRESS,1,1,BME280_REGISTER_T1
i2c read BME280_ADDRESS,0,6,cal%()
T1=cal%(0) OR (cal%(1)<< 8)
T2=cal%(2) OR (cal%(3)<< 8): if T2 and s16b then T2=T2 OR s16 'sign extend if required
T3=cal%(4) OR (cal%(5)<< 8): if T3 and s16b then T3=T3 OR s16
'
i2c write BME280_ADDRESS,1,1,BME280_REGISTER_P1
i2c read BME280_ADDRESS,0,18,cal%()
P1=cal%(0) OR (cal%(1)<<8)
P2=cal%(2) OR (cal%(3)<<8): if P2 and s16b then P2=P2 OR s16 'sign extend if required
P3=cal%(4) OR (cal%(5)<<8): if P3 and s16b then P3=P3 OR s16
P4=cal%(6) OR (cal%(7)<<8): if P4 and s16b then P4=P4 OR s16
P5=cal%(8) OR (cal%(9)<<8): if P5 and s16b then P5=P5 OR s16
P6=cal%(10) OR (cal%(11)<<8): if P6 and s16b then P6=P6 OR s16
P7=cal%(12) OR (cal%(13)<<8): if P7 and s16b then P7=P7 OR s16
P8=cal%(14) OR (cal%(15)<<8): if P8 and s16b then P8=P8 OR s16
P9=cal%(16) OR (cal%(17)<<8): if P9 and s16b then P9=P9 OR s16
'
i2c write BME280_ADDRESS,1,1,BME280_REGISTER_H1
i2c read BME280_ADDRESS,0,1,H1
i2c write BME280_ADDRESS,1,1,BME280_REGISTER_H2
i2c read BME280_ADDRESS,0,7,cal%()
H2=cal%(0) OR (cal%(1)<< 8): if H2 and s16b then H2=H2 OR s16 'sign extend if required
H3=cal%(2)
H6=cal%(6): if H6 and s8b then H6=H6 OR s8 'sign extend if required
H4=(cal%(3)<<4) OR (cal%(4) and &H0F): if H4 and s12b then H4=H4 OR s12 'sign extend if required
H5=(cal%(5)<<4) OR (cal%(4)>>4): if H5 and s12b then H5=H5 OR s12
'
i2c write BME280_ADDRESS,0,2,BME280_REGISTER_CONTROLHUMID,&H05 '16x oversampling humidity
i2c write BME280_ADDRESS,0,2,BME280_REGISTER_CONTROL,&HB7 '16x oversampling pressure/temp, normal mode
'
end sub
'
function q(x as integer) as integer 'returns 2 raised to the power
q=(1<<x)
End CFunction