Anyone used the Bosch BMP085 I2C baro sensor yet ?

[mr.sneezy]

Hi all,

If anyones used this new digital barometric sensor yet I'd love to see the PBP code to get calibrated readings out of it. I'm doing an open source project for R/C telemetry and using this sensor with a PIC16F819 is one of the first steps for me...

http://www.bosch-sensortec.com/conte...5-DS000-05.pdf

It's not just a simple I2C device (or I wouldn't be asking). It contains calibration data that must be referenced against an internal temperature sensor every time you calculate pressure (or altitude in this case). The math is a little more complex than I'm used too.

Anyway. I thought I'd ask here, might save me many migraines :-)

Thanks,
Martin

[BrianT]

Hello Martin,

I just scanned the Bosch datasheet. Their sensor is very similar to the Intersema MS5561C. The coding is more complex for the Bosch and the package will be tough to prototype I reckon. Have a look at the Intersema MS5540C. It is an easy package for hand solder prototyping. The Intersema range converts in about 35 mSecs. The Bosch unit at 7.5 mS has advantages in this area. Unless you need the speed I would have a go at the Intersema.

The MS5540C is under $20 qty 1 at Digikey which is where I get them.

HTH
BrianT

[ScaleRobotics]

Thanks Brian, I had not seen that sensor before. Nice catch.

Martin,

Don't know if you saw it already, but sparkfun has some C sample code here:
http://www.sparkfun.com/commerce/pro...oducts_id=9694

Sometimes it helps me to look at, even though I don't know C very well.

I ordered their board, but they are out of stock right now.

Walter

[Acetronics2]

Hi,

Also have a look to this one ...

reminds you some other ???

Alain

[mr.sneezy]

Thanks Brian, I had not seen that sensor before. Nice catch.

Martin,

Don't know if you saw it already, but sparkfun has some C sample code here:
http://www.sparkfun.com/commerce/pro...oducts_id=9694

Sometimes it helps me to look at, even though I don't know C very well.

I ordered their board, but they are out of stock right now.

Walter

Thanks Walter and Brian.

Brian I'm already committed to the Bosch sensor, and I have one on the way to me. Bare sensors are $8.95US at Sparkfun which is hard to beat.
I'd like to use it in this project as it has a good track record for use in altimeter devices. The soldering of this device shouldn't be too hard if you have some SMD experience (lots in my case). Or tip it upside down like another guy has and solder wires on top.

Walter I didn't C the C code at Sparkfun but I did find some in another website here
http://www.pixelproc.net/varios.html
I downloaded the C code, but it's all double dutch to me unfortunately. Maybe it will help you.
Walter maybe we can share some code when we have the devices.

Martin

[rsocor01]

Bare sensors are $8.95US at Sparkfun which is hard to beat.

Check this sensors out.

http://futurlec.com/Pressure_Sensors.shtml

Robert

[BrianT]

The FuturLec prices are excellent but I fear the HP03D will give highly variable results depending on incident light intensity. All silicon strain gauges are light sensitive. The HP01 and HP02 ones, coated in black, will be OK. The Intersema MS554x are light dependent even though they have opaque white 'silicone snot' covering the strain gauge element to reduce, but not eliminate, this effect.

Another trap with all these sensors is that distorting the ceramic substrate will bring out very large pressure and temperature offsets. In my experience, proper SMD reflow oven soldering does not stress the subsrtate anywhere like as much as hand soldering where the thermal stresses build up as each pin is soldered individually. I have found mounting the chip upside down and hand soldering fine 0.010 inch or 0.25 mm wire wrap wires keeps a batch tracking very well. You will not see the stress effects if you only make one or two units but if you build a batch of 100+ the difference unit to unit can be very frustrating.

The Hope HP03 has a cute feature of an on-board oscillator. I use the CCP registers of a PIC to provide the 32768 Hz MClk to the Intersema snsor but sometimes I would rather use a watch crystal direct on the pressure sensor instead of tying up a CCPWM port.

Lastly, most of the pressure sensor application notes specify a large tantalum cap across the supply. 47 uF in the case of the Intersema. The leakage current of this cap exceeds the sleep current of the sensor so don't forget that when you calculate your battery life.

HTH

BrianT

[mr.sneezy]

Thanks Brian.

Yes this is a one off project not a big batch, although hopefully many other RC model enthusiasts will build themselves one as it's part of an open source telemetry project using 2.4Ghz.

The sensor is actually available mounted on a small PCB for about $10 more. That may be the safest option.

I think the datasheet says only light through the small air hole is a problem on this sensor, so that should be easy to cover with something like carbon foam (antistatic chip foam).

Looks like I'm pioneering this sensor with PBP, hopefully you guys can help me cross the hard stuff when I get there in a week or so.
Martin

[ScaleRobotics]

Sparkfun has more of their BMP085 boards in stock now, if anyone is interested. Makes it nice to breadboard with. With the board, the cost is about the same as the Intersema. Still waiting on mine.

[mr.sneezy]

I've got my BMP085 now, and I'm using a serial LCD and a PIC12F683 to try converse with the sensor initially. I have a problem with i2c comms, and reading the datasheet it mentions 'Restart condition' between starting a conversion (temperature in this case for simplicity to see it changing) and reading the result.
Now I've not come across the 'restart condition' before with i2c chips (just EEPROMS thus far).

Is it done in the PBP i2c statements or does it need to be bit-banged ? Or am I up the whole wrong tree here altogether ?

Cheers all,
MArtin

[BrianT]

PBP gives you four choices for ShiftIn and ShiftOut to set the clock idle high/low and whether the shift is MSB or LSB first. This should cover your needs with the exception that PBP does NOT give you much control over the timing of the clock and data lines. There is a DEFINE SHIFT_PAUSEUS nn command but this only delays the clock/data transition at the start of the bit and there is no control over timing at the end of the bit.

Cable length, cloick & data slew speed and any ringing on the clock and data lines can give bulk grief that takes days to find. Been there done that.

I found with the intersems sensors that the potted PBP ShiftIn/Out routines would only drive about 300 mm of ribbon cable but my hand written bit bang method let me run over a metre of cable.

Intersema is not the same as the Bosch interface. DIn, DOut and SClk vs SDA and SCL but otherwise the chips are very similar so the same sort of code structure ought to work.

Here is how I do it.

OutShift:
   for fa = 1 to clockbits  
      'Don't forget OutShift adds an extra clock bit at the end. 
      din = (1 & iword)   'select lowest bit via AND mask 
      pauseus 4   'want minimum - about 4 uS or so
      sclk = 4 : pauseus 4 : sclk = 0
      iword = iword >> 1    'get next LSB, clock out zeros after 16 bits
   next fa
      sclk = 1 : pauseus 4 : sclk = 0 
      'this is the extra clock per DA5541B_00513 datasheet page 13
return

ResetIntersema:      ' resets ALL pressure sensors
'   shiftout din, sclk, 0, [85, 85, 0\5]  ' Sense of Din is IN to 5541
   output din  : output sclk
   clockbits = 20 : iword = %0101010101010101     '16 bit data word
   gosub outshift
return

ConvertDelay:        ' specific to each sensor
   if tank = 0 then
      While dout0 = 1 
      wend   
   endif      
   if tank = 1 then
      While dout1 = 1 
      wend
   endif   
   if tank = 2 then
      While dout2 = 1 
      wend
   endif
return

FetchWord: ' read specific channel reply.  Different pins for DOut0,1,2
   input dout0 : input dout1 : input dout2 : output sclk : iword = 0     
   if tank = 0 then
      for fa = 15 to 0 step -1   'need 17 clock bits so add one at end
         sclk = 1 : pauseus 4    'wait for Intersema to present next bit
         iword.0[fa] = dout0     'read the bit on selected channel
         sclk = 0                'drop clock
      next fa                    'do it 16 times
   endif
   if tank = 1 then
      for fa = 15 to 0 step -1   'need 17 clock bits so add one at end
         sclk = 1 : pauseus 1    'wait for Intersema to present next bit
         iword.0[fa] = dout1     'read the bit
         sclk = 0                'drop clock
      next fa                     'do it 16 times
   endif
   if tank = 2 then
      for fa = 15 to 0 step -1   'need 17 clock bits so add one at end
         sclk = 1 : pauseus 1    'wait for Intersema to present next bit
         iword.0[fa] = dout2     'read the bit
         sclk = 0                'drop clock
      next fa                    'do it 16 times
   endif
      sclk = 1 : pauseus 1 : sclk = 0  ' 17th clock bit 
      ii = iword.byte0 : ij = iword.byte1
return

ReadFactoryCal:   
      ' This unpacks the factory calibration coefficients from the just
      ' read W1 ~ W4.
      ' These bitmaps are unpacked into the 6 working coefficients
      ' C1 to C6 which are then stored in EEROM for later use.  
'W1
   gosub resetintersema
'   shiftout din, sclk, 0, [87, 1\5]    ' Send W1 pattern to all sensors
   clockbits = 12 : iword = %000101010111  'request W1 pattern
   gosub outshift
   gosub fetchword                     ' recall selected Tank reply
   W1.byte0 = ii
   W1.byte1 = ij
   if (w1 = 0) or (w1 = 65535) then 
      debug "W1 error", 13, 10
      goto readfactorycal
   endif

'W2    
   gosub resetintersema
'   shiftout din, sclk, 0, [215, 0\5]       ' Send W2 pattern 
   clockbits = 12 : iword = %000011010111
   gosub outshift
   gosub fetchword
   W2.byte0 = ii
   W2.byte1 = ij
   if (w2 = 0) or (w2 = 65535) then 
      debug "W2 error", 13, 10
      goto readfactorycal
   endif

'W3
   gosub resetintersema
'   shiftout din, sclk, 0, [55, 1\5]       ' Send W3 pattern
   clockbits = 12 : iword = %000100110111
   gosub outshift   
   gosub fetchword
   W3.byte0 = ii
   W3.byte1 = ij
   if (w3 = 0) or (w3 = 65535) then 
      debug "W3 error", 13, 10
      goto readfactorycal
   endif

'W4    
   gosub resetintersema
'   shiftout din, sclk, 0, [183, 0\5]       ' Send W4 pattern 
   clockbits = 12 : iword = %000010110111
   gosub outshift
   gosub fetchword
   W4.byte0 = ii
   W4.byte1 = ij
   if (w4 = 0) or (w4 = 65535) then 
      debug "W4 error", 13, 10
      goto readfactorycal
   endif

CalcCoefficients:     ' this serves all three sensors.
'C1
    C1 = W1 >> 3                      'unpack coefficient
    read (108 + tank*20), z.byte0   'store
    read (109 + tank*20), z.byte1
    if z<>c1 then
      write (108 + tank*20), c1.byte0   'store
      write (109 + tank*20), c1.byte1
    endif
'C2
    C2 = ((W1 & %0000000000000111) << 10) + (W2 >> 6)
    read (110 + tank*20), z.byte0
    read (111 + tank*20), z.byte1
    if z<>c2 then
      write (110 + tank*20), c2.byte0
      write (111 + tank*20), c2.byte1
    endif
'C3
    C3 = W3 >> 6
    read (112 + tank*20), z.byte0
    read (113 + tank*20), z.byte1
    if z<>c3 then
      write (112 + tank*20), c3.byte0
      write (113 + tank*20), c3.byte1
    endif
'C4    
    C4 = W4 >> 7
    read (114 + tank*20), z.byte0
    read (115 + tank*20), z.byte1
    if z<>c4 then
      write (114 + tank*20), c4.byte0
      write (115 + tank*20), c4.byte1
    endif
'C5
    C5 = ((W2 & %0000000000111111) << 6) + (W3 & %0000000000111111)
    read (116 + tank*20), z.byte0
    read (116 + tank*20), z.byte0
    if z<>c5 then
      write (117 + tank*20), c5.byte1
      write (117 + tank*20), c5.byte1
    endif
'C6
    C6 = W4 & %0000000001111111
    read (118 + tank*20), z
    if z<>c6 then
      write (118 + tank*20), c6
    endif

Show5541Coefficients:   'only used during diagnostics
'   high txd : pause 1
'   debug 13, 10, "Tank #", #tank, ", W1 = ", #w1, ",  W2 = ",_
'    #w2, ",  W3 = ", #w3, ",  W4 =  ", #w4, 13, 10
'   debug "Derived coeffs C1 = ", #C1, ", C2 = ", #C2, ", C3 = ",_
'    #C3, ", C4 = ", #c4, ", C5 = ", #C5, ", C6 = ", #C6, 13, 10

return

HTH

BrianT

[mr.sneezy]

Thanks Brian,

I'm not sure quite what to say though. I'm sure the tip I need is in the reply, but most of the answer went over my head.
I've not used shiftin/shiftout of anything in PBP so I'd rather get the i2c commands to work for me (if it's possible).
The sensor is 20mm from the PIC, so I'm hoping distance related issues should not be a problem. I'll just have a quiet little play with the i2c commands and see if I can get some sense out of it with that for now :-)
Thanks,
Martin

[mr.sneezy]

OK, got comms up. I can read the temperature sensor fine now. The issue was HW not SW this time.
Martin

[mr.sneezy]

Well I've spent a few hours working on this over the weekend, and I've made good progress (for me) with communicating with the sensor. I have a PIC Serial LCD (20x4) attached to a PIC12F683, which has the BMP085 attached to GPIO.0 (clock) and GPIO.1(data).

So far I can see the inbuilt temperature sensor value changing when I put a warm finger on the sensor, and also read out the eleven 16bit calibration parameters and display them (I think).

I'm worried about two things.
One is if I have the MSB and LSB of the calibration data in the right order when I'm storing them and then again using them. I not convinced the numbers look right on the LCD. The PBP manual I find confuses me somewhat when they talk about storing the LSB first in a word sized array of the i2c device (i2cread command description).

The second is converting this math to PBP, given that the values of some seem to be signed and results of some operations are going to be 32bit size (unless I don't understand it at all, which is possible).
To convert the raw temperature result UT to Deg C (T) is
X1 = (UT - AC6) * AC5 / 2^15
X2 = MC * 2^11 / (X1 + MD)
B5 = X1 + X2
T = (B5 + 8) / 2^4

I'd love some help with some code to show how this can be done in PBP.
Anybody ?

Cheers,
Martin

'PIC 12F683 port/pin allocations
'-------------------------------
'GPIO.0/Pin 7 = I2C SCL clock
'GPIO.1/Pin 6 = I2C SDA data
'GPIO.2/Pin 5 = spare
'GPIO.3/Pin 4 = spare
'GPIO.4/Pin 3 = LED
'GPIO.5/Pin 2 = Serial TX

'-----------------------
' PIC Defines
' ===========
'Config bits set to INTERNAL OSC, Watch dog ON, Power up timer ON, Master Clear NOT used, BrownOut protection ON, 
@ Device  pic12f683, intrc_osc, wdt_on, pwrt_on, mclr_off, bod_on ;Config switches, different from PBP default
'@ __Config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _PWRTE_ON & _MCLRE_OFF   ;USING MPASM ONLY

    Define Osc 4 '4Mhz clock used. Note - Set PIC config fuses on programmer to use Internal RC OSC
    
    Include "modedefs.bas"          ' Include serial modes

' Define some constants if needed
        
' Software Defines
    Cal_table   var word[11]         '11 word array to store calibration data
    Temp_Var    var byte             'temp variable 
    Temp_Var2   var Word	         'temp variable 
    i2c_Reg     var Byte             'variable for target i2c register address
    
    CPIN        var     GPIO.0       ' I2C clock pin 
    DPIN        var     GPIO.1       ' I2C data pin
    SO          Var     GPIO.5        'Serial out pin
    LED         var     GPIO.4        'Indicator LED, via 500ohm to +3.3V
    
'Alias's for calibration data in the sensor to match the Bosch paramater 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
    AC4     var     Cal_table[3]     'Lowbyte is MSB, Highbyte is LSB
    AC5     var     Cal_table[4]     'some values are signed (not AC4, AC5, AC6)
    AC6     var     Cal_table[5]    
    B1      var     Cal_table[6]
    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 either 12F629 or 12F675
' --------------------
    VRCON.7 = %0    'Comparator voltage reference OFF
    CMCON0 = %111   'Comparator inputs to OFF, all pins normal I/O
    ANSEL = 0       'Turn off al AD's     rem out for PIC12F629, use for PIC12F675

' Set initial state of GPIO port pins as Input or Output

    TRISIO.0 = 0    'Input(0 = output, 1 = Input)
    TRISIO.1 = 0    '
    TRISIO.2 = 1    '
    TRISIO.3 = 0    '
    TRISIO.4 = 0    '
    TRISIO.5 = 1    '

' PIC initialization code

        Low LED     'LED on
        pause 500
        High LED    'LED off
 
        Serout SO,N2400,[$FE,$01]               ' Clear LCD & home LCD cursor.
        pause 10                                ' wait for LCD to catch up
        Serout SO,N2400,["   FrSky Vario    "]  ' Serial print 
        Serout SO,N2400,[$FE,$C0]               ' Shift cursor to line2
        Serout SO,N2400,[" development jig  "]  ' Serial print 
        Pause 3000
        
        i2c_Reg =$AA                            'Start address of calibration data
        I2CREAD DPIN,CPIN,$EF,I2C_REG,[STR Cal_table\11],read_error1  'Read 11 words out of sensor
        Serout SO,N2400,[$FE,$01]             ' Clear LCD & home LCD cursor. 
        Pause 10                              ' wait for LCD to catch up
Main:  
        Serout SO,N2400,[$FE,$02]             'home LCD cursor.                           
                
        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,[Temp_Var2],read_error  'Read temperature MSB, LSB.

        Serout SO,N2400,[#Temp_Var2," "]       'Send Word size number to LCD

'lets see whats in the cal data array for a checking math   
        Serout SO,N2400,[$FE,$C0]               ' Shift cursor to line2
        Serout SO,N2400,[#AC1," ",#AC2," ",#AC3]
        Serout SO,N2400,[$FE,$94]               ' Shift cursor to line3
        Serout SO,N2400,[#AC4," ",#AC5," ",#AC6]
        Serout SO,N2400,[$FE,$D4]
        Serout SO,N2400,[#B1," ",#B2," ",#MB]
'        ," ",#MC," ",#MD]                  '
        pause 1000
        Toggle LED
        Goto main
        
Read_error:
        Serout SO,N2400,[$FE,$01]             ' Clear LCD & home LCD cursor. 
        Pause 10                              ' wait for LCD to catch up
        Serout SO,N2400,["i2c bus read error"]       '        
        pause 250        
       
        Toggle LED
        Goto main
         
Read_error1:
        Serout SO,N2400,[$FE,$01]             ' Clear LCD & home LCD cursor. 
        Pause 10 
        Serout SO,N2400,["i2c cal read error "]       '        
        
End

[mr.sneezy]

Real values.
If there happens to be a mathematician amongst us that likes puzzles like the one above, I have the raw values (as decimal) read out of my sensor to plug into the temperature equations as a test. The result should be around 21C.

UT = 30814
AC5 = 22882
AC6 = 1368
MC = 48596
MD = 32777

[mr.sneezy]

UT = 30814
AC5 = 22882
AC6 = 1368
MC = 48596
MD = 32777

MC = -15828
MD = -9

A friend helped me use MS Excel to test the results I got out above. I missed that MC and MD are signed.
If MC is now -15828 and MD is now -9 then I get a result of T= 214 (+21.4C) in my lounge room...
So that would mean the MSB & LSB read out of the array IS the correct way around in my PIC code.

[mr.sneezy]

Ignore the cr@p I posted above. I thought I had it worked out but noooo.

PS. I hate the way you can't edit the post for more than a hour or so after putting up some info. What's with that anyway ?

[mackrackit]

PS. I hate the way you can't edit the post for more than a hour or so after putting up some info. What's with that anyway ?

Edits to post do not trigger a notification to those following a thread.

If edits were allowed to far back the whole context of the thread could be changed or useful information lost.

So there is really no reason to allow edits for more than a few minutes to correct spelling, grammar, or typos in general.

[mr.sneezy]

No the title is right....

I've just done some reading at Melabs about Longs in the recent versions of PBP and how they work with 18F series PIC's. I now think I may be doing sensor this the hard way with trying to use a 12F or 16F PIC.

A broad question: If the math involved in using this sensor only uses Longs and no floating point, can I use a 18FXXXX PIC to crunch the signed math, or is there a likely newbie Longs trap to fall into ?

I'd copy/paste the data sheets equations here to show you, but it's copy/paste protected. I'll attach it as a file.
It's only the last conversion from pressure to altitude that seems to use a float, and I can worry about that when I get that far (I hope). Page 12 is the guts of it.

[BrianT]

I have read the Bosch datasheet which is very similar to the Intersema MS5540 family. With the exception of absolute altitude, LONGs and a PIC18F part will handle those formulae easily.

The mathematical gymnastics of handling the Bosch 19 bit variables with 16 bit PBP will consume much code space thus ruling out the 12F series. You will get it into a 16F part on code space grounds but you will have to invent your own way to extend WORD variables up to 19 bits. Why bother?

The 18F series costs hardly any more, at least at hobby volumes, so cut your losses and go for a PIC18F part and take advantage of LONGs. This will automatically take care of negative temperatures which your altimeter will certainly need.

Absolute Altitude needs LOG functions to handle the power 1/5.255 so avoid that by using a lookup table which you can make as accurate as you want by adjusting the size of the table and the interpolation method.

HTH
BrianT

[mr.sneezy]

I have read the Bosch datasheet which is very similar to the Intersema MS5540 family. With the exception of absolute altitude, LONGs and a PIC18F part will handle those formulae easily.
HTH
BrianT

Hi Brian, yes that helps me, a good confidence boost at the very least.
Can I bother you a moment longer ? About two things in the datasheet that you may well understand without looking at it again.

First is that the equations for the temp and pressure conversions have in there a couple of times the value called 'oss', used with a binary shift I think. Do you know what that 'oss' means ?

Lastly, I've been reading the raw pressure value with my code as a 16 bit Word, but it occurred to me now that even if I don't specify the hi-res mode, that I should be reading the full 19bits (LSB being 000 I guess) not just 16. The data sheet doesn't make it clear either way (to me).

TIA,
Martin

[BrianT]

Looks to me the number of places you left or right shift is related to how many samples you take per reading. try and get hold of the C code and see if you can nut it out. In my Intersema code, I do the averaging by a simple sum of n readings divided by n at the end. Again, LONGs take the pain out of needing to know if the sum of 8 samples overflowed a 16 bit variable.

I have failed to find a copy of their C source code on the net. Seems you have to genuflect for one of their distributors to get it.

HTH
BrianT

[mr.sneezy]

Thanks Brian. Did I fail to RTFM :-) I hope not.

I studied a nicely done vario project here using the BMP085 and C30 compiler.
http://www.pixelproc.net/pic24bmp085lcd.html
Didn't mean much to me unfortunately as it's a very busy bit of work.

Yes, I like the simpler add many then divide way of averaging too, it always works well.
Martin

[mr.sneezy]

For anyone interested in the BMP085 barometric sensor I am now a little more sure that I've got a good set of calibration coefficients read out my BMP085, and also got the UT and UP raw values reading correctly.
I've set the BMP085 to it's highest resolution and over-sampling now (oss=3), and can use the 19bit size result in the Excel spreadsheet and get sensible results.
I did a test from the top of the building I work in, to the bottom, some 12 floors, and I get a altitude change of 63 meters which is about right. Then did one from the bottom to the top of the hill I live on and got a good result again.

While the code looks simple it turned out that it really needed to be using Longs and therefore a 18FXXXX micro. I had 18F1220 parts in my box so that's what I've used.
To display whats going on inside the PIC I use a PIC serial display, which I built many years ago (great bit of gear that). Mine has 20x4 LCD display rather than the usual 16x2 line.

I'll attach the Excel XLS file that my friend Andrew T made up using the calculations from the BMP085 datasheet. It processes the calibration data, temperature and pressure data the same way as I need my PIC too. So it's a good test comparison to see if my code is work right in each stage and has helped me greatly.

'PIC 18F1220 port/pin allocations
'-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
'PortA.0/Pin 1 = Serial TX
'PortA.1/Pin 2 = LED
'PortB.0/Pin 8 = I2C SCL clock
'PortB.1/Pin 9 = I2C SDA data
 
' -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
'Config Directive settings for MPASM (fuses)
 
@    __CONFIG  _CONFIG1H, _IESO_OFF_1H & _FSCM_OFF_1H & _INTIO2_OSC_1H
@    __CONFIG  _CONFIG2L, _PWRT_ON_2L & _BOR_ON_2L & _BORV_27_2L
@    __CONFIG  _CONFIG2H, _WDT_ON_2H & _WDTPS_32K_2H
@    __CONFIG  _CONFIG3H, _MCLRE_OFF_3H
@    __CONFIG  _CONFIG4L, _DEBUG_OFF_4L & _LVP_OFF_4L & _STVR_OFF_4L
@    __CONFIG  _CONFIG5L, _CP0_OFF_5L & _CP1_OFF_5L
@    __CONFIG  _CONFIG5H, _CPB_OFF_5H & _CPD_OFF_5H
@    __CONFIG  _CONFIG6L, _WRT0_OFF_6L & _WRT1_OFF_6L
@    __CONFIG  _CONFIG6H, _WRTC_OFF_6H & _WRTB_OFF_6H & _WRTD_OFF_6H
@    __CONFIG  _CONFIG7L, _EBTR0_OFF_7L & _EBTR1_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
    lTemp_Var   var Long             'Long temporary variable
    Temp_Var    var byte             'Byte temp variable 
    Temp_Var2   var Word	         'Word temp variable
    Temp_Var3   var word             'Word temp variable
    UTemp       var word             'uncompensated temp reading
'    UPres       var word             'uncompensated pressure reading
    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
    
'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]     'some values are signed (not AC4, AC5, AC6)
    AC6     var     Cal_table[5]    
    B1      var     Cal_table[6]
    B2      var     Cal_table[7]
    MB      var     Cal_table[8]
    MC      var     Cal_table[9]    
    MD      var     Cal_table[10]    
    
' Initialize Processor - check for each PIC type 
' -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
    ADCON1 = %11111111              '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 

'    Include "modedefs.bas"          ' Include serial modes    

' Set initial state of port pins as Input or Output

    TRISA = %11111100    'Input(0 = output, 1 = Input)
    TRISB = %11111100    '
    
' PIC initialization code
        Low So      'Must start low, or you get rubbish on the LCD at PIC boot up.
        Low LED     'LED on
        pause 5000  'led on for x seconds
        High LED    'LED off
        
        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 3000                               'wait three seconds
        
        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 
                               
        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, not cleared.                           
         
        Gosub Read_temp                        'get Temp via I2C

        lTemp_var = 0                          'Clear the last pressure reading
        For Temp_var = 0 to 9                  'start of 10x averaging routine
        Gosub Read_pres                        'get Long uncompensated pressure via I2C
        lTemp_var = ltemp_var + lUpres
        Next Temp_var
        lUpres = lTemp_Var / 10               'finish of 10x Averaging routine
        
        Serout2 SO,16780,["UT=",DEC utemp," "]       'Send Word size number to LCD
        Serout2 SO,16780,["UP=",DEC luPres," "]      'Send Word size number to LCD
                
'lets see whats in the cal data array for a checking math in Excel - Rem out Utemp and lUpres above 
'        Serout2 SO,16780,[$FE,$2]               ' Shift cursor to line_1 (128+addr) Note-Rem out Utemp and lUpres above
'        Serout2 SO,16780,[SDEC AC1," ",SDEC AC2," ",SDEC AC3]   'display three signed cal values
        Serout2 SO,16780,[$FE,$C0]               ' Shift cursor to line_2
        Serout2 SO,16780,[DEC AC4," ",DEC AC5," ",DEC AC6]   'display three unsigned cal values
        Serout2 SO,16780,[$FE,$94]               ' Shift cursor to line_3  
        Serout2 SO,16780,[SDEC B1," ",SDEC B2]   'display two signed cal values
        Serout2 SO,16780,[$FE,$D4]               ' Shift cursor to line_4          
        Serout2 SO,16780,[SDEC MB," ",SDEC MC," ",SDEC MD]  'display three signed cal values
 '        pause 100
        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(not needed).
        lUpres = lUpres >> 13                 'remove result from $F9 (>>8) + left shift result back to 19bits (>>5)
                                              '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,[Utemp],I2C_error  'Read temperature MSB, LSB.
        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

Now I have to convert this code below to PBPL and get a 'compensated' reading of the temperature and pressure.... Quite a few intermediate variables are needed.

//calculate the temperature
x1 = (ut - ac6) * ac5 >> 15;
x2 = ((int32_t) mc << 11) / (x1 + md);
b5 = x1 + x2;
temperature = (b5 + 8) >> 4;

//calculate the pressure
b6 = b5 - 4000;
x1 = (b2 * (b6 * b6 >> 12)) >> 11;
x2 = ac2 * b6 >> 11;
x3 = x1 + x2;
b3 = ((int32_t) ac1 * 4 + x3 + 2) >> 2;
x1 = ac3 * b6 >> 13;
x2 = (b1 * (b6 * b6 >> 12)) >> 16;
x3 = ((x1 + x2) + 2) >> 2;
b4 = (ac4 * (uint32_t) (x3 + 32768)) >> 15;
b7 = ((uint32_t) up - b3) * 50000;
p = b7 < 0x80000000 ? (b7 * 2) / b4 : (b7 / b4) * 2;

x1 = (p >> 8) * (p >> 8);
x1 = (x1 * 3038) >> 16;
x2 = (-7357 * p) >> 16;
pressure = p + ((x1 + x2 + 3791) >> 4);

I found this above C code elsewhere on the Web, it's in the datasheet more or less. I've also had PBP code help from a few forum members. Thank you all for the help so far

The journey continues...

[mr.sneezy]

Hmm...
I've written all the 32Bit calculation code now using PBPL and Longs, where they are needed (well nearly everywhere).
Right away I got a list of very strange compiler errors like this
c:/pbp/pbppi18l.lib 695 : Argument out of range ( 4168 not between 0 and 4095)

After having a look at line 695 of that file I still had no clue. So I took a punt that I might have run out of PIC code space, and yes that seems to be right. If I select a PIC in the same sub family with more code space the code complies error free....
Longs sure burn code space like it was endless resource.
Off to find a another bigger PIC again. This will be the 4th PIC tried for this project.


Onward and upwards !!

PS. Is there a simple to use utility, MCS add-on or method that will show me the amount of RAM space my code is using when compiled (as well as program space) ?

[Acetronics2]

Hmm...
I've written all the 32Bit calculation code now using PBPL and Longs, where they are needed (well nearly everywhere).
Right away I got a list of very strange compiler errors like this
c:/pbp/pbppi18l.lib 695 : Argument out of range ( 4168 not between 0 and 4095)

After having a look at line 695 of that file I still had no clue. So I took a punt that I might have run out of PIC code space, and yes that seems to be right. If I select a PIC in the same sub family with more code space the code complies error free....
Longs sure burn code space like it was endless resource.
Off to find a another bigger PIC again. This will be the 4th PIC tried for this project.


Onward and upwards !!

Hi,

Looks linked to too small a program memory ... in 18 pins ... the 1320 exists in 8k ...

Alain

[mr.sneezy]

Hi Alain,

Yes, it compiles OK if I select that one, at about 5200 bytes.

As I have to buy the next size PIC I might as well jump to the 18F2520 with huge code space and 28pins, although I really am only using a few I/O at the moment. Going to be lots of unused I/O's.

Martin

[ScaleRobotics]

PS. Is there a simple to use utility, MCS add-on or method that will show me the amount of RAM space my code is using when compiled (as well as program space) ?

Nice work on the sensor code!

MCS shows you how much code is being used at the bottom of the page after compliling. (Note it does need a successful compile to be able to tell you this.)



You can also peek in the .lst file, and find code used vs left.

MEMORY USAGE MAP ('X' = Used,  '-' = Unused)


0000 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX
0040 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX
0080 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX
00C0 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX
0100 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX
0140 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX
0180 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXX-------
0200 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX
0240 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX
0280 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX
02C0 : XXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXX ---------------- ----------------
2000 : -------X-------- ---------------- ---------------- ----------------

All other memory blocks unused.

Program Memory Words Used:   665
Program Memory Words Free:   359

Then there is also Darrel's CodeSpace utility here:
http://www.picbasic.co.uk/forum/showthread.php?t=2418

[mr.sneezy]

Nice work on the sensor code!

Thanks, although it's not complete just yet. I'll show you the main sensor code snip in case you are interested. It complies now (if selecting a bigger PIC) and I know the result of the lCTemp section is 100% correct (+ & - Deg C ). The UPres calculations are as of right now untested.
If you see any blindingly obvious code bloat in the calculations let me know...
I will post the complete code as soon as I know it works fine.

I did know what the code size used was telling me in MCS, I was more curious about RAM (variables etc) as I have been caught before going to a PIC with more code space, only to be quickly stumped by running out of variables...

All variables are signed Longs, except MD, AC5 and AC6 which are Words.

'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 << 11) / (X1 + MD)            'Find X2
        B5 =  X1 + X2                           'Find B5 from X1 and X2
        lCTemp = (B5 + 8) / 16                  'Hey presto, lCTemp appears... 
          
'Calculate pressure in Pa from 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) << 5) / 4         'My OSS = 3 (might need to * here not <<)
        x1 = (lac3 * b6) / $2000
        x2 = (b1 * (b6 * b6 / $1000)) / $10000
        x3 = ((x1 + x2) + 2) / 4
        B4 = (lac4 * (x3 + 32768)) / $8000
        B7 = (lUPres - B3) * 50000
        If B7 < $80000000 then 
            lPres = (B7 * 2) / B4
        Else
            lPres = (B7 / B4) * 2
        Endif
        X1 = (lPres / 256) * (lPres / 256)
        X1 = (X1 * 3038) / $10000
        X2 = (-7357 * lPres) / $10000
        lPres = lPres + ((X1 + X2 + 3791) / 16)

        Serout2 SO,16780,["T=",DEC lCtemp,"    "]       'Send Word size number to LCD
        Serout2 SO,16780,["P=",DEC lPres,"     "]      'Send Word size number to LCD

[ScaleRobotics]

Sorry I missed the RAM part (even though it was in capitals...)

If my memory serves me correctly, I think the only way to test your ram space is to create a large dummy array, and see how large you can make it. If you get an error, make it smaller, to see what you have left. Yes, it would be nice if MCS counted your RAM

[rore85]

Hi... I'm new in this forum and I need your help about how to manage data from BMP085 in assembler... I need test it in a PIC16f84...

[ScaleRobotics]

Hi... I'm new in this forum and I need your help about how to manage data from BMP085 in assembler... I need test it in a PIC16f84...

That sounds a bit like torture for most of us. The math is hard enough using the longs feature in PBP, and a more robust PIC18F device. You might try the Microchip forum, as they are into that kind of thing (assembly). Likely they will help, but not do it for you.

Good luck,

Walter

[mr.sneezy]

Hi... I'm new in this forum and I need your help about how to manage data from BMP085 in assembler... I need test it in a PIC16f84...

Hi, If you can get a PIC16F84 to read and process the data from a BMP085 into true pressure and temperature I'll eat my shorts !!

My program has hit 5.5Kb in code size on an 18F PIC. Sure I know assembly is much much tighter, but by that much ?

I will soon post (I hope so) the complete code to use this sensor on a PIC18FXXXX device with PBP. You can use the ASM file I guess to see how blocks of it are done in assembly.
Cheers,
Martin

[Acetronics2]

Hi, Sneezzy

I Think , with little trickery, the 16F84 could fit ...

let's think ...

IF you calculate the linearisation OUTSIDE the Pic, and trunk it to the PRECISION claimed ( not the resolution, eh ...)
...

I'm sure a lookup table, or a couple of " ax+b " regressions could be used.

But that implies ... the sensor and the PIC are married for life !!!

Alain

[mr.sneezy]

Hi, Sneezzy

I Think , with little trickery, the 16F84 could fit ...

let's think ...

IF you calculate the linearisation OUTSIDE the Pic, and trunk it to the PRECISION claimed ( not the resolution, eh ...)
...

I'm sure a lookup table, or a couple of " ax+b " regressions could be used.

But that implies ... the sensor and the PIC are married for life !!!

Alain

I did think of that early on. I think you need to map all possible pressure readings (at your needed precision) across your range, but then also map for every possible temperature change across all pressure readings in that range. I think it very quickly becomes an impressive size lookup table yes ?
I suspect my shorts are safe, but if the poster above can do it I'll listen :-)

[Acetronics2]

Hi, Martin

I had a look to your excel sheet and , of course, got THE problem ...

solution was to unlock the sheet , select the "F16" place and click on " place a formula " ( Fx button ) ...

it automatically corrects the written formula and then it rolls fine !!!

Are the Calibration values in the sheet those of YOUR Sensor ???

Alain

[mr.sneezy]

Hi, Martin

I had a look to your excel sheet and , of course, got THE problem ...

solution was to unlock the sheet , select the "F16" place and click on " place a formula " ( Fx button ) ...

it automatically corrects the written formula and then it rolls fine !!!

Are the Calibration values in the sheet those of YOUR Sensor ???

Alain

Hi Alain, I suspect my friend didn't tell me that so I couldn't fiddle with his sheet

Yes, that indeed is the calibration data out of my BMP085 sensor.

Good news.
Tonight I finished debugging the pressure calculations and got a correct result in Pascals. Boy it took some doing didn't it. :-)
Tomorrow I'll tidy up the code and post the whole job after doing a little field testing.

Now I need to find a sample of a 'good' way to do a look-up table to convert pressure to altitude without using Logs (as I understand is required)...

Martin

[Acetronics2]

Hi, Martin

Was an awful job to crack the sheet password I had to wait for the second attempt to get it open ...

May be ...

an excel sheet could easily produce the retrieve table to include in the program ???

I already did that for a programmable electronic ignition project ...

Alain

[rore85]

Thanks for answer...
I wonder if the calibration coefficients of BMP085 depend on something ... as either light, or are the same constants for all?
And another thing, the uncompensated temperature varies a lot ... in the order of thousands or hundreds
Thanks

[mr.sneezy]

Hi, Martin

Was an awful job to crack the sheet password I had to wait for the second attempt to get it open ...

May be ...

an excel sheet could easily produce the retrieve table to include in the program ???

I already did that for a programmable electronic ignition project ...

Alain

Yes, I guess it could be done that way. I wonder how much data in the table is just enough, that might be hard to workout ?
Yes the sensor would be mated by the table to one PIC for life, and make it impossible to give the HEX file to anyone else to use for an open project (if they can't use PBP). Unless the table can be forced into a known place in code space perhaps... Messy at the very least.