PBP 2.60 and MCS 4.0.0.0Originally Posted by eab123
Martin
PS. If you do something interesting with the code please let us in on it :-)
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PBP 2.60 and MCS 4.0.0.0
Martin
PS. If you do something interesting with the code please let us in on it :-)
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Re: Anyone used the Bosch BMP085 I2C baro sensor yet ?
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......
Roger
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What result precision shall I expect from the module - sampling methods
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)?
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
Roger
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"Resolution" or "precision" or whatever....
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
Furthermore, what's the "rms noise" meaning?
Last edited by flotulopex; - 11th January 2012 at 06:17.
Roger
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Re: "Resolution" or "precision" or whatever....
...really nobody can help?
Roger
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