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Mainly temperature dependant. I've not been able to show much sensitivity to light yet (indoors).Quote:
Originally Posted by rore85
Yes, the pressure reading is very 'active' so I used the maximum OSS and then 10x averaging as well. It could do with even more...
Here it is. This works, and give you a corrected temperature and pressure reading from a Bosch BMP085 barometric pressure sensor.
It requires a PIC18FXXXX MCU and use of PBPL compiler option. You'll need to change the configs for whatever PIC you choose and change the Serout2 statements to LCDOUT or whatever you want to display data on.
The main point of this post is really to show the calculations and variable casting and manipulation required.
Code:'******************************************************************************
'MR.SNEEZY - test code for FrSky using Bosch BMP085 baro sensor.
'This version is for PIC 18F4620
'
'ADD/Do
'
'NOTES -
'
'LAST ACTION - scratch my head...
'
'PIC 18F1220 port/pin alocations
'-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
'PortA.0/Pin 2 = Serial TX
'PortA.1/Pin 3 = LED
'PortB.0/Pin 33 = I2C SCL clock
'PortB.1/Pin 34 = I2C SDA data
' -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
'Config Directive settings for MPASM (fuses) for 18F4620
@ __CONFIG _CONFIG1H, _IESO_OFF_1H & _FCMEN_OFF_1H & _OSC_INTIO7_1H
@ __CONFIG _CONFIG2L, _PWRT_ON_2L & _BOREN_OFF_2L
@ __CONFIG _CONFIG2H, _WDT_OFF_2H & _WDTPS_512_2H
@ __CONFIG _CONFIG3H, _MCLRE_OFF_3H & _PBADEN_OFF_3H
@ __CONFIG _CONFIG4L, _DEBUG_OFF_4L & _LVP_OFF_4L & _STVREN_OFF_4L & _XINST_OFF_4L
@ __CONFIG _CONFIG5L, _CP0_OFF_5L & _CP1_OFF_5L & _CP2_OFF_5L & _CP3_OFF_5L
@ __CONFIG _CONFIG5H, _CPB_OFF_5H & _CPD_OFF_5H
@ __CONFIG _CONFIG6L, _WRT0_OFF_6L & _WRT1_OFF_6L & _WRT2_OFF_6L & _WRT3_OFF_6L
@ __CONFIG _CONFIG6H, _WRTC_OFF_6H & _WRTB_OFF_6H & _WRTD_OFF_6H
@ __CONFIG _CONFIG7L, _EBTR0_OFF_7L & _EBTR1_OFF_7L & _EBTR2_OFF_7L & _EBTR3_OFF_7L
@ __CONFIG _CONFIG7H, _EBTRB_OFF_7H
DEFINE OSC 8 '8Mhz clock used.
' Define some constants if needed
' Software Defines (variables and pins)
Cal_table var word[11] '11 word array to store calibration data
lUpres var long 'Long variable for Uncompensated Pressure
lPres var Long 'Long variable for Compensated Pressure
lTemp_Var1 Var long 'Long temporary variable
X1 var Long
X2 var Long
X3 var Long
B3 var long
B4 var long
B5 var long
B6 var Long
B7 var long
lAC1 var Long 'Long variables for cal values actually negative in my sensor
lAC2 var long 'These are 'cast' from the Word vars into Long vars in code below
lAC3 var Long
lAC4 var Long
lMB var Long
lMC var Long
bTemp_Var1 var byte 'Byte temp variable
wTemp_Var1 var Word 'Word temp variable
wTemp_Var2 var word 'Word temp variable
lUTemp var long 'Uncompensated temperature reading from sensor
lCTemp var Long 'Compensated (real) temperature x10 (1/10th of C) from sensor
i2c_Reg var Byte 'variable for target i2c register address
CPIN var PortB.0 ' I2C clock pin
DPIN var PortB.1 ' I2C data pin
SO Var PortA.0 'Serial out pin
LED var PortA.1 'Indicator LED, via 500ohm to +3.3V
OSS con $3 'This value is the Over Sampling Setting for the BMP085
'0 = minimum, 3 = maximum. Also change value in Read_pres if you alter OSS
'Alias's for calibration data in the sensor to match the Bosch parameter list names
AC1 var Cal_table[0] '
AC2 var Cal_table[1] 'BMP085 has 11 16bit values stored in EEPROM
AC3 var Cal_table[2] 'First byte is at $AA last at $BF, two bytes per cal value
AC4 var Cal_table[3] 'Lowbyte is MSB (e.g $AA), Highbyte is LSB (e.g. $AB)
AC5 var Cal_table[4] '
AC6 var Cal_table[5]
B1 var Cal_table[6] 'Warning - AC4, AC5, AC6 are UNSIGNED values, the rest are SIGNED
B2 var Cal_table[7]
MB var Cal_table[8]
MC var Cal_table[9]
MD var Cal_table[10]
' Initialise Processor - check for each PIC type
' -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
ADCON1 = %00001111 'Turn off all AD's
' OSCCON = %01100111 'set INTRC to 4 MHZ
OSCCON = %01110111 'set INTRC to 8 MHZ
' OSCTUNE = 0 'OSC trim set to Null
' Set initial state of port pins as Input or Output if needed
' TRISA = %11111100 'Input(0 = output, 1 = Input)
' TRISB = %11111100 '
' TRISC = %11111111
' TRISD = %11111110
' TRISE = %11111111
' PIC initialization code
' Low So 'Start low, or you get rubbish on the LCD at PIC boot up.
Gosub Alive 'Go prove the PIC is running via LED
Serout2 SO,16780,[$FE,$01] ' Clear LCD & home LCD cursor.
pause 10 ' wait for LCD to catch up
Serout2 SO,16780,[" FrSky Vario "] ' Serial print
Serout2 SO,16780,[$FE,$C0] ' Shift cursor to line2
Serout2 SO,16780,[" Development Jig "] ' Serial print
Pause 2000
i2c_Reg =$AA 'Start address of the BMP085 calibration data
I2CREAD DPIN,CPIN,$EF,I2C_REG,[STR Cal_table\11],cal_error 'Read 11 reversed words out of sensor
AC1 = (AC1.lowbyte<<8) + AC1.highbyte 'swap MSB and LSB of each to use in PBP (un-reverse then)
AC2 = (AC2.lowbyte<<8) + AC2.highbyte 'device stores the MSB in the Low byte, LSB in the High byte
AC3 = (AC3.lowbyte<<8) + AC3.highbyte
AC4 = (AC4.lowbyte<<8) + AC4.highbyte
AC5 = (AC5.lowbyte<<8) + AC5.highbyte
AC6 = (AC6.lowbyte<<8) + AC6.highbyte
B1 = (B1.lowbyte<<8) + B1.highbyte
B2 = (B2.lowbyte<<8) + B2.highbyte
MB = (MB.lowbyte<<8) + MB.highbyte
MC = (MC.lowbyte<<8) + MC.highbyte
MD = (MD.lowbyte<<8) + MD.highbyte
'Cast (convert) signed PBP Word vars to signed PBP Long vars where needed by math routines below
lAC1 = AC1 'copy word to long
if AC1.15 then lAC1.HIGHWORD = $FFFF 'Check for negative, set top 16bits to all 1's if true
lAC2 = AC2 'copy word to long
if AC2.15 then lAC2.HIGHWORD = $FFFF 'Check for negative, set top 16bits to all 1's if true
lAC3 = AC3 'copy word to long
if AC3.15 then lAC3.HIGHWORD = $FFFF 'Check for negative, set top 16bits to all 1's if true
lMB = MB 'copy word to long
if MB.15 then lMB.HIGHWORD = $FFFF 'Check for negative, set top 16bits to all 1's if true
lMC = MC 'copy word to long
if MC.15 then lMC.HIGHWORD = $FFFF 'Check for negative, set top 16bits to all 1's if true
'Cast (convert) UN-signed PBP Word var to UN-signed PBP Long var for math routines below
lAC4 = AC4 'copy word to long, both unsigned
Serout2 SO,16780,[$FE,$01] ' Clear LCD & home LCD cursor.
Pause 10 ' wait for LCD to catch up
'Main loop -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Main:
Serout2 SO,16780,[$FE,$02] 'home LCD cursor, LCD not cleared.
Gosub Read_temp 'get Temp via I2C
Serout2 SO,16780,["UT=",SDEC lUtemp," "] 'Send Word size number to LCD
lTemp_Var1 = 0 'Clear the last pressure reading
For bTemp_Var1 = 0 to 9 'Start of 10x averaging routine
Gosub Read_pres 'get Long uncompensated pressure via I2C
lTemp_Var1 = lTemp_Var1 + lUpres
Next bTemp_Var1
lUpres = lTemp_Var1 / 10 'finish of the 10x Averaging routine
Serout2 SO,16780,["UP=",SDEC lUpres," "] 'Send Word size number to LCD
'Calculate temperature in 1/10ths of Deg C from lUTemp ' Note 2^15 = 32768 Dec or $8000
X1 = ((lUtemp - AC6) * AC5) / $8000 'find X1.
X2 = (lMC * $800) / (X1 + MD) 'Find X2. Note:- math rounding results in X2 being in error by 1 ?
B5 = X1 + X2 'Find B5 from X1 and X2.
lCTemp = (B5 + 8) / 16 'Hey presto, lCTemp appears...
'DISPLAY true temperature in C
X1 = lCTemp / 10 'find value above decimal point
Serout2 SO,16780,[$FE,$C0] ' Shift cursor to line_2
Serout2 SO,16780,["Temp= ",DEC X1,"."] 'Send Word size number to LCD
X1 = lCTemp // 10 'Find decimal value
Serout2 SO,16780,[DEC X1," "] 'Send Word size number to LCD
'Calculate pressure in Pascals from uncompensated pressure lUpres (1/100th's of hPa's)
B6 = b5 - 4000
x1 = (b2 * (B6 * B6 / $1000)) / $800
x2 = (lac2 * B6) / $800
x3 = x1 + x2
B3 = ((lac1 * 4 + x3) << OSS + 2) / 4 'OSS = Over Sampling constant set above
x1 = (lac3 * b6) / $2000
x2 = (b1 * (b6 * b6 / $1000)) / $10000
x3 = ((x1 + x2) + 2) / 4
B4 = (lac4 * (x3 + 32768)) / $8000 'Find B4, note lAC4 is an unsigned Long
B7 = (lUPres - B3) * (50000 >> OSS) 'OSS = Over Sampling constant set above
If B7 < $80000000 then 'branch if value is above or below range
lPres = (B7 * 2) / B4
Else
lPres = (B7 / B4) * 2
Endif
X1 = (lPres / 256) * (lPres / 256)
X1 = (X1 * 3038) / $10000 '$10000 = 2^16
X2 = (-7357 * lPres) / $10000
lPres = lPres + (X1 + X2 + 3791) / 16 'lPres is the true pressure in Pa
'DISPLAY true pressure in hPa
X1 = lPres / 100 'find value above decimal point
Serout2 SO,16780,[$FE,$94] 'Shift cursor to line_3
Serout2 SO,16780,["hPa= ",DEC X1,"."] 'Send Word size number to LCD
X1 = lPres // 100 'find value below decimal point
Serout2 SO,16780,[DEC X1," "] 'Send Word size number to LCD
pause 1000
Toggle LED 'flash the 'im alive' LED
Goto main
'SUBROUTINES -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Read_pres:
i2c_Reg = $F4 '$F4 is the control register address
I2CWRITE DPIN,CPIN,$EE,I2C_REG,[$F4] ' Write $34+(oss << 6) to set pressure conversion
Pause 30 ' Delay 10ms after each write (30mS for HiRes results (oss=3))
i2c_Reg = $F6 '$F6 is the result register MSB
I2CREAD DPIN,CPIN,$EF,I2C_REG,[lUpres],I2C_error 'Read pressure MSB, LSB, XLSB, $F9 ($F9 not actually wanted).
lUpres = lUpres >> (16 - oss) 'remove $F9 from result (>>8), and left shift result back to 16 to 19 Bits (OSS value dependant)
'it's because PBP reads four bytes if [Var] is a long...
return 'we only want top 19bits of the result.
Read_temp:
i2c_Reg = $F4 '$F4 is the control register address
I2CWRITE DPIN,CPIN,$EE,I2C_REG,[$2E] ' Write $2E to set temperature conversion
Pause 10 ' Delay 10ms after each write
i2c_Reg = $F6 '$F6 is the result register MSB
I2CREAD DPIN,CPIN,$EF,I2C_REG,[wTemp_Var1],I2C_error 'Read temperature MSB, LSB.
lUTemp = wTemp_Var1 'copy word to long. Note BMP085 UT is NOT a signed value
return
'Prove it's alive
Alive:
High LED 'flash LED routine
For btemp_var1 = 10 to 110 step 10
Low LED
Pause bTemp_Var1
High LED
Pause bTemp_Var1
Next bTemp_Var1
Return
'trap and display I2C problems
I2C_error:
Serout2 SO,16780,[$FE,$01] ' Clear LCD & home LCD cursor.
Pause 10 ' wait for LCD to catch up
Serout2 SO,16780,["i2c bus read error"] 'no ACK from I2C device
pause 2000
Toggle LED
Goto main
Cal_error:
Serout2 SO,16780,[$FE,$01] ' Clear LCD & home LCD cursor.
Pause 10
Serout2 SO,16780,["i2c cal read error "] '
End
Hi everybody...Quote:
Originally Posted by rore85
The program in assembler works but I have problems generated in a division ratio, ie, it is rounded to an integer and the final value of the temperature goes too far in the real value, almost 80 degrees more ...
Someone had the same problem?
Thanks in advance!
Here are some multi byte division functions for assembly: http://avtanski.net/projects/math/
Hi Martin-
Thanks for sharing the Bosch code with us- some undertaking.
I'm just about to start a small project that could use this device and thought I'd just check I can compile it correctly using your posted code for the 18F4620 before proceeding further.
Unfortunately I'm getting compile errors ("overwriting previous address contents 0000 to 0007 locations") and just wondering if you could give me the versions of Microstudio and PBP you are running- I'm running Microstudio 3.0.0.5 and PBP 2.50L (with the pbpl box checked!)
Thanks for your time.
Edward
You need to set the configs correctly
http://www.picbasic.co.uk/forum/showthread.php?t=543
Thanks- all ok now.
PBP 2.60 and MCS 4.0.0.0Quote:
Originally Posted by eab123
Martin
PS. If you do something interesting with the code please let us in on it :-)
Hello,
I was wondering if someone did make a piece of PB code for converting the pressure to altitude?
I'm far too bad in maths......
Hi there,
I have played around with mr.sneezy's code and came up with that one hereunder. Appart from the temperature,I use only raw data for my tests (makes the code a little smaller).
The serial comm settings have been changed to connect to a pc-terminal (i.e. Serial Communicator in MCS) instead of a serial LCD display to make it more handy to store data into an EXCEL sheet for analysis.
I'm using three sampling methods:
1.- all measured values added and divided by the number of measurements ("16/16")
2.- keep 8 middle measurements out of sixteen and average them ("Mid8/16")
3.- keep 4 lowest (Bottom) and 4 highest (Top) measurements out of sixteen and average them ("B4+T4/16")
The "Diff" shows the variation +/- with the previous value to have a rought idea about the result of each sampling method.
Question: I'm wondering what precision I can expect from the BOSCH sensor. I'm not used to what one can expect from that type of sensor. While my sensor is "sitting" on my table,the values are bouncing up and down. I this correct?
As a parglider pilot, I use an alti-variometer from FlyTec 4010 and the ascent/descent speed (precision is up to 0,1m per second) does not vary if the instruments isn't moved up or down. How can I reach the same behaviour from my sensor (no "bouncing" or no wrong ascent/descent indication)?
Attachment 6213
Code:'******************************************************************************
'MR.SNEEZY - test code for FrSky using Bosch BMP085 baro sensor.
'This version is for PIC 18F4620
'
'PIC 18F4620 port/pin alocations
'-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
'PortA.0/Pin 2 = Serial TX
'PortA.1/Pin 3 = LED
'PortB.0/Pin 33 = I2C SCL clock
'PortB.1/Pin 34 = I2C SDA data
'Config Directive settings for MPASM (fuses) for 18F4620
@ __CONFIG _CONFIG1H, _IESO_OFF_1H & _FCMEN_OFF_1H & _OSC_INTIO7_1H
@ __CONFIG _CONFIG2L, _PWRT_ON_2L & _BOREN_OFF_2L
@ __CONFIG _CONFIG2H, _WDT_OFF_2H & _WDTPS_512_2H
@ __CONFIG _CONFIG3H, _MCLRE_OFF_3H & _PBADEN_OFF_3H
@ __CONFIG _CONFIG4L, _DEBUG_OFF_4L & _LVP_OFF_4L & _STVREN_OFF_4L & _XINST_OFF_4L
@ __CONFIG _CONFIG5L, _CP0_OFF_5L & _CP1_OFF_5L & _CP2_OFF_5L & _CP3_OFF_5L
@ __CONFIG _CONFIG5H, _CPB_OFF_5H & _CPD_OFF_5H
@ __CONFIG _CONFIG6L, _WRT0_OFF_6L & _WRT1_OFF_6L & _WRT2_OFF_6L & _WRT3_OFF_6L
@ __CONFIG _CONFIG6H, _WRTC_OFF_6H & _WRTB_OFF_6H & _WRTD_OFF_6H
@ __CONFIG _CONFIG7L, _EBTR0_OFF_7L & _EBTR1_OFF_7L & _EBTR2_OFF_7L & _EBTR3_OFF_7L
@ __CONFIG _CONFIG7H, _EBTRB_OFF_7H
'Registers
ADCON1 = 001111 'Turn off all AD's
OSCCON = 110111 'set INTRC to 8 MHZ
DEFINE OSC 8 '8Mhz clock used.
' SO_pinftware Defines (variables and pins)
Cal_table VAR WORD[11] '11 word array to store calibration data
lUpres VAR LONG 'Uncompensated Pressure
lPres VAR LONG 'Compensated Pressure
DataA VAR LONG 'or WORD - as needed
ArraySize CON 16
RawData VAR LONG[ArraySize] 'or WORD - as needed
X1 VAR LONG
X01 VAR LONG
X2 VAR LONG
X3 VAR LONG
B3 VAR LONG
B4 VAR LONG
B5 VAR LONG
B6 VAR LONG
B7 VAR LONG
lAC1 VAR LONG 'cal values actually negative in my sensor
lAC2 VAR LONG 'These are 'cast' from the Word vars into Long vars in code below
lAC3 VAR LONG
lAC4 VAR LONG
lMB VAR LONG
lMC VAR LONG
bTemp_Var1 VAR BYTE 'temp variable
wTemp_Var1 VAR WORD 'temp variable
wTemp_Var2 VAR WORD 'temp variable
lUTemp VAR LONG 'Uncompensated temperature reading from sensor
lCTemp VAR LONG 'Compensated (real) temperature x10 (1/10th of C) from sensor
lTemp_Var1 VAR LONG
lTemp_Var2 VAR LONG
lTemp_Var3 VAR LONG
Tempo1 VAR LONG
Tempo2 VAR LONG
Tempo3 VAR LONG
I2C_Reg VAR BYTE 'target i2c register address
Counter VAR WORD 'loop counter to show on display
Counter = 0
S_Bd_Rate VAR WORD
S_Bd_Rate = 84 '9600DTN
LF CON 10 'Line Feed (for use with Serial Terminal like Hyperterminal)
CR CON 13 'Carriage Return (for use with Serial Terminal like Hyperterminal)
OSS_Res CON $3 'Over Sampling Setting for the BMP085
OSS_Time CON 30 'in ms for OSS_Res 0 = 10ms, ..., 3 = 25ms (see BMP085 datasheet)
I2C_SCL VAR PortB.0 'I2C clock pin
I2C_SDA VAR PortB.1 'I2C data pin
S_TX VAR PortA.0 'Serial Tx) out pin
LED VAR PortA.1 'Indicator LED, via 500ohm to +3.3V
'Aliases for calibration data in the senS_TXr to match the Bosch parameter list names
AC1 VAR Cal_table[0] '
AC2 VAR Cal_table[1] 'BMP085 has 11 16bit values stored in EEPROM
AC3 VAR Cal_table[2] 'First byte is at $AA last at $BF, two bytes per cal value
AC4 VAR Cal_table[3] 'Lowbyte is MSB (e.g $AA), Highbyte is LSB (e.g. $AB)
AC5 VAR Cal_table[4] '
AC6 VAR Cal_table[5]
B1 VAR Cal_table[6] 'Warning - AC4, AC5, AC6 are UNSIGNED values, the rest are SIGNED
B2 VAR Cal_table[7]
MB VAR Cal_table[8]
MC VAR Cal_table[9]
MD VAR Cal_table[10]
I2C_Reg =$AA 'Start address of the BMP085 calibration data
I2CREAD I2C_SDA,I2C_SCL,$EF,I2C_Reg,[STR Cal_table\11],Cal_error 'Read 11 reversed words out of sensor
AC1 = (AC1.LOWBYTE<<8) + AC1.HIGHBYTE 'swap MSB and LSB of each to use in PBP (un-reverse then)
AC2 = (AC2.LOWBYTE<<8) + AC2.HIGHBYTE 'device stores the MSB in the Low byte, LSB in the High byte
AC3 = (AC3.LOWBYTE<<8) + AC3.HIGHBYTE
AC4 = (AC4.LOWBYTE<<8) + AC4.HIGHBYTE
AC5 = (AC5.LOWBYTE<<8) + AC5.HIGHBYTE
AC6 = (AC6.LOWBYTE<<8) + AC6.HIGHBYTE
B1 = (B1.LOWBYTE<<8) + B1.HIGHBYTE
B2 = (B2.LOWBYTE<<8) + B2.HIGHBYTE
MB = (MB.LOWBYTE<<8) + MB.HIGHBYTE
MC = (MC.LOWBYTE<<8) + MC.HIGHBYTE
MD = (MD.LOWBYTE<<8) + MD.HIGHBYTE
'Cast (convert) signed PBP Word vars to signed PBP Long vars where needed by math routines below
lAC1 = AC1 'copy word to long
IF AC1.15 THEN lAC1.HIGHWORD = $FFFF 'Check for negative, set top 16bits to all 1's if true
lAC2 = AC2 'copy word to long
IF AC2.15 THEN lAC2.HIGHWORD = $FFFF 'Check for negative, set top 16bits to all 1's if true
lAC3 = AC3 'copy word to long
IF AC3.15 THEN lAC3.HIGHWORD = $FFFF 'Check for negative, set top 16bits to all 1's if true
lMB = MB 'copy word to long
IF MB.15 THEN lMB.HIGHWORD = $FFFF 'Check for negative, set top 16bits to all 1's if true
lMC = MC 'copy word to long
IF MC.15 THEN lMC.HIGHWORD = $FFFF 'Check for negative, set top 16bits to all 1's if true
'Cast (convert) UN-signed PBP Word var to UN-signed PBP Long var for math routines below
lAC4 = AC4 'copy word to long, both unsigned
'Main loop
'-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
MAIN:
'Get Temp via I2C
I2C_Reg = $F4 '$F4 is the control register address
I2CWRITE I2C_SDA,I2C_SCL,$EE,I2C_Reg,[$2E] 'Write $2E to set temperature conversion
PAUSE 10 'Delay 10ms after each write
I2C_Reg = $F6 '$F6 is the result register MSB
I2CREAD I2C_SDA,I2C_SCL,$EF,I2C_Reg,[wTemp_Var1],I2C_error'Read temperature MSB, LSB.
lUTemp = wTemp_Var1 'copy word to long. Note BMP085 UT is NOT a signed value
'Calculate temperature in 1/10ths of Deg °C from lUTemp ' Note 2^15 = 32768 Dec or $8000
X1 = ((lUTemp - AC6) * AC5) / $8000 'Find X1.
X2 = (lMC * $800) / (X1 + MD) 'Find X2. Note:- math rounding results in X2 being in error by 1 ?
B5 = X1 + X2 'Find B5 from X1 and X2.
lCTemp = (B5 + 8) / 16 'Hey presto, lCTemp appears...
'Assign true temperature in °C in "x.x" format
X1 = lCTemp / 10 'find value above decimal point
X01 = lCTemp // 10 'Find decimal value
'Take 16 measures from the BMP085
lTemp_Var1 = 0 'Clear the last pressure reading
FOR bTemp_Var1 = 0 TO 15 'Start of 16x averaging routine
I2C_Reg = $F4 '$F4 is the control register address
I2CWRITE I2C_SDA,I2C_SCL,$EE,I2C_Reg,[$F4] 'Write $34+(oss << 6) to set pressure conversion
PAUSE OSS_Time 'Delay 10ms after each write (30mS for HiRes results (oss=3))
I2C_Reg = $F6 '$F6 is the result register MSB
I2CREAD I2C_SDA,I2C_SCL,$EF,I2C_Reg,[lUpres],I2C_error 'Read pressure MSB, LSB, XLSB, $F9 ($F9 not actually wanted).
lUpres = lUpres >> (16 - OSS_Res) 'remove $F9 from result (>>8), and left shift result back to 16 to 19 Bits (OSS value dependant)
lTemp_Var1 = lTemp_Var1 + lUpres
RawData(bTemp_Var1) = lUpres 'fill-up array for sorting & averaging
NEXT bTemp_Var1
lUpres = lTemp_Var1 / 16 'finish of the 10x Averaging routine
'Melanie's "sorting number" algorythm - ordonate data
bTemp_Var1 = 0
SortLoop:
IF RawData(bTemp_Var1 + 1) < RawData(bTemp_Var1) THEN
DataA = RawData(bTemp_Var1)
RawData(bTemp_Var1) = RawData(bTemp_Var1 + 1)
RawData(bTemp_Var1 + 1) = DataA
IF bTemp_Var1 > 0 THEN bTemp_Var1 = bTemp_Var1-2
ENDIF
bTemp_Var1 = bTemp_Var1 + 1
IF bTemp_Var1 < (ArraySize -1) THEN GOTO SortLoop
'display data array
'for bTemp_Var1 = 0 to (ArraySize -1)
' Serout2 S_TX,S_Bd_Rate,[dec2 bTemp_Var1, " ", dec rawdata(bTemp_Var1),LF]
'next
'**** Additional SAMPLING METHODS ****
'keep the eight middle values and average them
lTemp_Var2 = 0
FOR bTemp_Var1 = 4 TO 11
lTemp_Var2 = lTemp_Var2 + RawData(bTemp_Var1)
NEXT bTemp_Var1
lTemp_Var2 = lTemp_Var2 / 8
'keep Bottom 4 (B4) and top 4 (T4) and average them
lTemp_Var3 = 0
FOR bTemp_Var1 = 0 TO 3
lTemp_Var3 = lTemp_Var3 + RawData(bTemp_Var1)
NEXT bTemp_Var1
FOR bTemp_Var1 = 12 TO 15
lTemp_Var3 = lTemp_Var3 + RawData(bTemp_Var1)
NEXT bTemp_Var1
lTemp_Var3 = lTemp_Var3 / 8
'find the differences with the previous values
IF lUpres > Tempo1 THEN
Tempo1 = lUpres - Tempo1
ELSE
Tempo1 = Tempo1 - lUpres
ENDIF
IF lTemp_Var2 > Tempo2 THEN
Tempo2 = lTemp_Var2 - Tempo2
ELSE
Tempo2 = Tempo2 - lTemp_Var2
ENDIF
IF lTemp_Var3 > Tempo3 THEN
Tempo3 = lTemp_Var3 - Tempo3
ELSE
Tempo3 = Tempo3 - lTemp_Var3
ENDIF
'Display all data
SEROUT2 S_TX,S_Bd_Rate,["16/16 = ",DEC lUpres," Diff = ",DEC Tempo1, LF]
SEROUT2 S_TX,S_Bd_Rate,["Mid8/16 = ",DEC lTemp_Var2," Diff = ",DEC Tempo2, LF]
SEROUT2 S_TX,S_Bd_Rate,["B4+T4/16 = ",DEC lTemp_Var3," Diff = ",DEC Tempo3, LF]
SEROUT2 S_TX,S_Bd_Rate,["Temp = ",DEC X1,".",DEC X01,"°C",LF]
SEROUT2 S_TX,S_Bd_Rate,["Counter = ",DEC Counter,LF,CR]
PAUSE 1000
Tempo1 = lUpres
Tempo2 = lTemp_Var2
Tempo3 = lTemp_Var3
Counter = Counter + 1
TOGGLE LED 'flash the 'im alive' LED
GOTO MAIN
'Trap and display I2C problems
I2C_error:
SEROUT2 S_TX,S_Bd_Rate,["i2c bus read error",LF,CR]
PAUSE 2000
TOGGLE LED
GOTO MAIN:
Cal_error:
SEROUT2 S_TX,S_Bd_Rate,["i2c cal read error ",LF,CR]
PAUSE 2000
TOGGLE LED
GOTO MAIN:
END
...yes, it's quite cold in my lab :wink:
Here is the latest BMP085's datasheet (rev 1.3 - August 22nd 2011).
I need to understand how one can use this sensor and have a stable 0,1m reading. I just don't get it :dispirited:
Furthermore, what's the "rms noise" meaning?
Attachment 6220
...really nobody can help?