BMP085 Bosch Sensortec, BMP085 Datasheet - Page 13

• Manufacturer Part Number: BMP085
• Description: DIGITAL BAROMETRIC PRESSURE SNSR
• Manufacturer: Bosch Sensortec

Specifications of BMP085

• Pressure Type: Absolute
• Operating Pressure: 4.35 ~ 15.95 PSI, 300 ~ 1100 hPa
• Port Size: Female, 0.591" (1.5mm) Flush
• Output: Digital
• Voltage - Supply: 1.62 V ~ 3.6 V
• Termination Style: Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 8-CLCC
• For Use With: 828-1012 - BMP085 DAUGHTERCARD FOR DEV KIT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 828-1005-2

Calculation of pressure and temperature for BMP085
UT = MSB << 8 + LSB
UP = (MSB<<16 + LSB<<8 + XLSB) >> (8-oss)
X1 = (UT - AC6) * AC5 / 2
X2 = MC * 2
B5 = X1 + X2
T = (B5 + 8) / 2
B6 = B5 - 4000
X1 = (B2 * (B6 * B6 / 2
X2 = AC2 * B6 / 2
X3 = X1 + X2
B3 = ((AC1*4+X3) << oss + 2) / 4
X1 = AC3 * B6 / 2
X2 = (B1 * (B6 * B6 / 2
X3 = ((X1 + X2) + 2) / 2
B4 = AC4 * (unsigend long)(X3 + 32768) / 2
B7 = ((unsigned long)UP - B3) * (50000 >> oss)
if (B7 < 0x80000000) { p = (B7 * 2) / B4 }
X1 = (p / 2
X1 = (X1 * 3038) / 2
X2 = (-7357 * p) / 2
p = p + (X1 + X2 + 3791) / 2
else { p = (B7 / B4) * 2 }
read reg 0xF6 (MSB), 0xF7 (LSB), 0xF8 (XLSB)
read out E
read uncompensated temperature value
display temperature and pressure value
write 0x34+(oss<<6) into reg 0xF4, wait
read uncompensated pressure value
write 0x2E into reg 0xF4, wait 4.5ms
read reg 0xF6 (MSB), 0xF7 (LSB)
from the E
8
) * (p / 2
11
calculate true temperature
2
/ (X1 + MD)
calculate true pressure
PROM registers, 16 bit, MSB first
Read calibration data
4
AC2 (0xAC, 0xAD)
AC1 (0xAA, 0xAB)
AC3 (0xAE, 0xAF)
AC4 (0xB0, 0xB1)
AC5 (0xB2, 0xB3)
AC6 (0xB4, 0xB5)
11
13
MC (0xBC, 0xBD)
MB (0xBa, 0xBB)
MD (0xBE, 0xBF)
B1 (0xB6, 0xB7)
B2 (0xB8, 0xB9)
16
8
2
16
PROM of the BMP085
)
Start
12
12
2
)) / 2
)) / 2
1 5
4
16
11
15
(16 bit)
(16 bit)
(16 bit)
(16 bit)
(16 bit)
(16 bit)
(16 bit)
(16 bit)
(16 bit)
(16 bit)
(16 bit)
example:
AC1 =
AC2 =
AC3 =
AC4 =
AC5 =
AC6 =
B1 =
B2 =
MB =
MC =
MD =
UT =
oss =
= oversampling_setting
(ultra low power mode)
UP =
X1 =
X2 =
B5 =
T =
B6 =
X1 =
X2 =
X3 =
B3 =
X1 =
X2 =
X3 =
B4 =
B7 =
p =
X1 =
X1 =
X2 =
p =
1171050000
-14383
-32768
27898
23843
32741
32757
23153
33457
70003
74529
69964
-8711
-2344
-1601
-7859
6190
2868
4743
2399
2810
3454
408
150
422
717
-72
56
57
59
4
0
1
C code function:
bmp085_get_cal_param
bmp085_get_ut
bmp085_get_up
bmp085_get_temperature
temp in 0.1° C
BMP085_calpressure
press. in Pa
type:
short
short
short
unsigned short
unsigned short
unsigned short
short
short
short
short
short
long
short (0 .. 3)
long
long
long
long
long
long
long
long
long
long
long
long
long
unsigned long
unsigned long
long
long
long
long
long
long