bma180 accelerometer with I2C

seiko99 · 2012-07-15 10:07

I finally got a quickstart board and need to quickly get started on what I thought would be a simple project of connecting this breakout board I got from sparkfun.
I have dug and dug for any projects with sample code I can look at using this thing and can't find a thing. I think that quad copters since they use propellers is clouding the search engines - lol

This is such a great sensor and has been out so long, surely someone has done something with it. I started an object file with all the registers and values and have been trying to modify the c code that is on the sparkfun site, but I guess the jump to spin is too much for me.

I have been at it almost every evening for almost 2 weeks and am getting nowhere. Help?

Mike Green · 2012-07-15 10:43

I haven't seen any examples here on this chip's use. It's a pretty complex looking part with lots of options which may be why there's not any evidence of interest. How are you doing the I2C part of things? There are a number of objects that will handle that part for you. They take an I2C address and I/O pin numbers plus a register address in the BMA180 and take care of transferring bytes to and from the device. "Basic_I2C_Driver" is one such object.

To read from a BMA180 register if the BMA180 SCL is <SCL pin> and SDA is on the next higher I/O pin do:

Z := i2c.ReadByte(<SCL pin>, <device>, i2c#OneAddr | <register>)

To write to a BMA180 register do:

i2c.WriteByte(<SCL pin>, <device>, i2c#OneAddr | <register>, <data to write>)

The <device> code is the 8-bit byte that selects the device. It's the device address (a 7-bit number) shifted left one bit to make the byte sent to the device. The least significant bit of this byte is always zero for these routines. The BMA180 allows for two different device addresses depending on the setting of one of the device's pins. See the datasheet for details.

Similarly, you can read or write multiple bytes from / to successive BMA180 registers. See the comments in Simple_I2C_Driver for details.

seiko99 · 2012-07-16 16:46

Mike Green wrote: »

I haven't seen any examples here on this chip's use. It's a pretty complex looking part with lots of options which may be why there's not any evidence of interest. How are you doing the I2C part of things? There are a number of objects that will handle that part for you. They take an I2C address and I/O pin numbers plus a register address in the BMA180 and take care of transferring bytes to and from the device. "Basic_I2C_Driver" is one such object.

To read from a BMA180 register if the BMA180 SCL is <SCL pin> and SDA is on the next higher I/O pin do:

Z := i2c.ReadByte(<SCL pin>, <device>, i2c#OneAddr | <register>)

To write to a BMA180 register do:

i2c.WriteByte(<SCL pin>, <device>, i2c#OneAddr | <register>, <data to write>)

The <device> code is the 8-bit byte that selects the device. It's the device address (a 7-bit number) shifted left one bit to make the byte sent to the device. The least significant bit of this byte is always zero for these routines. The BMA180 allows for two different device addresses depending on the setting of one of the device's pins. See the datasheet for details.

Similarly, you can read or write multiple bytes from / to successive BMA180 registers. See the comments in Simple_I2C_Driver for details.

I just spent $60 bucks on ink to finally print out the datasheet. I have started with the Basic_i2c_driver and created my own object file containing all the registers for the bma180.
I was confused at first thinking that I had to use the prop's SCL and SDA. I am believing now that this is bit-bang and I can use whatever pins I want. I guess my biggest confusion comes from the examples that were put together by James Burrows (I think). The i2c object is initialized and then the object/device specific routines are initialized and used. They are so device specific, it is daunting as a first propeller project.

Anyways, I am pushing on and will post some code tonight hopefully. Your examples should help a lot. I am excited about the things I see with the propeller. Last year I built a machine with an arduino mega that drove me so crazy with the interrupt game that I almost gave up. I think once this little accelerometer starts doing what I need, I may have a mega for sale on ebay.

Mike Green · 2012-07-16 16:55

Basic_I2C_Driver is bit-bang, The only restriction on pin numbers is that the number passed to the I2C routines is that of SCL and SDA has to be the next higher numbered I/O pin. You can certainly use the same I2C pins used for the Prop's EEPROM, but you don't have to. James Burrows took the original Basic_I2C_Driver and added a bunch of device specific interfaces. If you have one of these devices, his routines will save some work. They also serve as examples of how to interface to devices similar to them.

seiko99 · 2012-07-16 19:32

OBJ
i2c : "Basic_I2C_Driver"
Ser : "Parallax Serial Terminal"

CON
_clkmode = xtal1 + pll16x 'Standard clock mode * crystal frequency = 80 MHz
_xinfreq = 5_000_000
BMA_CRC = $5B
BMA_OFFSETZ = $3A
BMA_OFFSETY = $39
BMA_OFFSETX = $38
BMA_OFFSETT = $37
BMA_OFFSETLSB2 = $36
BMA_OFFSETLSB1 = $35
BMA_GAINZ = $34
BMA_GAINY = $33
BMA_GAINX = $32
BMA_GAINT = $31
BMA_TCOZ = $30
BMA_TCOY = $2F
BMA_TCOX = $2E
BMA_CD2 = $2D
BMA_CD1 = $2C
BMA_SLOPETH = $2B
BMA_HIGHTH = $2A
BMA_LOWTH = $29
BMA_TAPSENSTH = $28
BMA_HIGHDUR = $27
BMA_LOWDUR = $26
BMA_HIGHLOWINFO = $25
BMA_SLOPETAPSENSINFO = $24
BMA_HY = $23
BMA_CTRLREG4 = $22
BMA_CTRLREG3 = $21
BMA_BWTCS = $20
BMA_RESET = $10
BMA_CTRLREG2 = $0F
BMA_CTRLREG1 = $0E
BMA_CTRLREG0 = $0D
BMA_STATUSREG4 = $0C
BMA_STATUSREG3 = $0B
BMA_STATUSREG2 = $0A
BMA_STATUSREG1 = $09
BMA_TEMPERATURE = $08
BMA_ACCZMSB = $07
BMA_ACCZLSB = $06
BMA_ACCYMSB = $05
BMA_ACCYLSB = $04
BMA_ACCXMSB = $03
BMA_ACCXLSB = $02
BMA_VERSION = $01
BMA_CHIPID = $00
BMA_address = $80
''Range setting
RANGESHIFT = 1
RANGEMASK =$0E
BWMASK = $F0
BWSHIFT = 4
i2cSCL = 26
i2cSDA = 27
bma180address = 00_0000
''interrupt_pin = 22 ''for when I figure out how to do that

VAR
long id
byte Z

PUB main
ser.Start(115_200)
waitcnt(clkfreq/10 + cnt) 'wait for things to settle

PUB init(range, bw) ''init bma180
''from advice:
Z := i2c.ReadByte(i2cscl, bma180address, i2c#bma180address | BMA_CHIPID)

This is where I am at for the moment. The "i2c#bma180address | BMA_CHIPID" is not making sense and is just me guessing. Maybe I am over analyzing.
Should it be i2c.ReadByte(i2cscl, bma180address, BMA_CHIPID) ? I see that the interpreter wants a constant if I do it the old way.

Thanks again for any help

seiko99 · 2012-07-22 17:27

Ok, I got it working. I used some of the c code from the sparkfun site on the bits, but I feel like I am not getting the full resolution or at least the numbers the way I need them. I want to put a routine that will test for changes over a certain amount. My current code does not indicate positive or negative when rendered in decimal. Thus a small movement will go from say 48 to 1432 when it crosses zero. This also screws with averaging. I want full 14 bit resolution. The MSB and LSB together consist of a 2's complement total of 16 bits with one data ready bit.

A piece of my code for one axis is as follows:

VAR
long id
word bmversion, temp, temp1, temp2, temp3, temp4, temptemp
long tempX, tempY, tempZ

PUB getX
repeat while temp <> 1
temp := i2cObject.readLocation(bmaddress, ACCXLSB) & $1
temp := i2cObject.readLocation(bmaddress, ACCXMSB)
temp2 := temp << 8
temp2 |= i2cObject.readLocation(bmaddress, ACCXLSB)
tempX := temp2 >> 2
temp := 0

I guess I should convert to signed decimal? Are the <> and other bitwise methods I am calling the right ones? Oh yeah, how about degrees?

seiko99 · 2012-07-27 15:15

This 14 bit number is making me nuts. I think that the Serial_Terminal.spin code is messing with me

VAR
  long id
  byte temp, i
  word bmversion, temp1, temp2, temp3, temp4, temptemp
  word tempX, tempY, tempZ

PUB getX
    repeat while temp <> 1  ''temp is a byte, temp2 and tempX are words
          temp := i2cObject.readLocation(bmaddress, ACCXLSB) & $1      ''check data ready bit
    temp := i2cObject.readLocation(bmaddress, ACCXMSB)
    temp2 := temp << 8  ''move MSB to position
    temp2 |= i2cObject.readLocation(bmaddress, ACCXLSB)
    tempX := temp2

I decided to not right shift, leaving a couple of flag bits in the word. It is really inconsequential if I can get the negative numbers (I would rather work with 14 bits). As it is, I only get positive.

        Ser.str(String("X: "))
        Ser.dec(tempX)

I tried setting tempX to $FF80 which should be negative 128. Still wont show negative. I printed out my words in binary and the sign bits are set.
I am playing around with numbers.spin, but not getting anywhere. Help?

Lawson · 2012-07-27 16:24

I think what's catching you is that all math in spin is done on 32-bit words. -128 would be $FFFF_FF80, etc.

Two easy ways to fix this. Use the "~~variable" 16-bit sign extension operator. (i.e. "tempX := ~~temp2" ) Or, to sign extend any word width, use the shift left and shift arithmetic right operators. (i.e. "tempX := (temp2 <<16) ~> 16" )

Lawson

seiko99 · 2012-08-11 14:07

Ok, this has been interesting. I now have the readings that I want from the serial terminal. It has been tough and the code is surely rough. My problem now is that I cannot start another cog to simply toggle some leds as a test. I am posting it all in the hopes that it might help.

OBJ
        i2cObject : "i2cObject"
        Ser  : "Parallax Serial Terminal"
        numb : "Numbers"
        f32     : "F32"
        fstring : "FloatString"
        
CON
        _clkmode = xtal1 + pll16x       'Standard clock mode * crystal frequency = 80 MHz
        _xinfreq = 5_000_000
        CRC                 = $5B
        OFFSETZ             = $3A
        OFFSETY             = $39
        OFFSETX             = $38
        OFFSETT             = $37
        O7LSB2          = $36
        OLSB1          = $35
        GAINZ               = $34
        GAINY               = $33
        GAINX               = $32
        GAINT               = $31
        TCOZ                = $30
        TCOY                = $2F
        TCOX                = $2E
        CD2                 = $2D
        CD1                 = $2C
        SLOPETH             = $2B
        HIGHTH              = $2A
        LOWTH               = $29
        TAPSENSTH           = $28
        HIGHDUR             = $27
        LOWDUR              = $26
        HIGHLOWINFO         = $25
        SLOPETAPSENSINFO    = $24
        HY                  = $23
        CTRLREG4            = $22
        CTRLREG3            = $21
        BWTCS               = $20
        RESET               = $10
        CTRLREG2            = $0F
        CTRLREG1            = $0E
        CTRLREG0            = $0D
        STATUSREG4          = $0C
        STATUSREG3          = $0B
        STATUSREG2          = $0A
        STATUSREG1          = $09
        TEMPERATURE         = $08
        ACCZMSB             = $07
        ACCZLSB             = $06
        ACCYMSB             = $05
        ACCYLSB             = $04
        ACCXMSB             = $03
        ACCXLSB             = $02
        VERSION             = $01
        CHIPID              = $00
        address             = $80
        ''Range setting
        RANGESHIFT              = 1
        RANGEMASK               =$0E
        BWMASK                  = $F0
        BWSHIFT                 = 4
        i2cSCLLine                  = 24
        i2cSDALine                  = 25
        bmaddress           = 00_0000
        interrupt_pin         = 0                    ''for when I figure out how to do that
        led                     = 23
        

VAR
  long id, temp
  long stacks[20]
  byte tempxlsb, tempxmsb, tempylsb, tempymsb, tempzlsb, tempzmsb, temptemp, temp1
  long avg_x, avg_y, avg_z, lastx, lasty, lastz
  word temp2, index
  long bmversion, pitch[numreadings], roll[numreadings], theta[numreadings]
  long tempY, tempZ, alarmcnt, noalarm
  long tempX, diff, devy, devz
  long readingsx[numreadings], readingsy[numreadings] 
  long readingsz[numreadings], devx, totalx, totaly, totalz, setp, setr, sett
  byte cogidnum
  
CON
  hyst = 180
  numreadings = 20
  ''stabilize = 100
  lsb = 0.00019


PUB start
  dira[led] := 1
  cognew(alarmcheck, @stacks)
  main
  
PUB main
  'f32.start
  dira[interrupt_pin]~

  Numb.init
  ser.Start(115_200)
  waitcnt(clkfreq/10 + cnt)   'wait for things to settle
  i2cObject.init(i2cSDALine,i2cSCLLine)   'pin numbers of the sda and scl lines to i2cobject
  init($0, $0)
  waitcnt(clkfreq/10 + cnt)   'wait for things to settle
  
  startup   ''get set points 
      ''if ina[interrupt_pin]
        ''8192 counts at 1g  4096 at 2g
        ''outa[led] := 1
  ''alarmcheck
  index :=  0

    repeat
        if index => numreadings
        ''debug
          index := 0
      ReadTemp
      ''getXYZ
          ''temp := 0
        repeat while temp <> 1  ''temp is a byte, temp2 and tempX are words
          temp := i2cObject.readLocation(bmaddress, ACCXLSB) & $1      ''check data ready bit
        tempxmsb := i2cObject.readLocation(bmaddress, ACCXMSB)
        temp2 := tempxmsb << 8  ''move MSB to position
        temp2 |= i2cObject.readLocation(bmaddress, ACCXLSB)
        temp2 := temp2 >> 2
        if tempxmsb > $7F
          tempX := $FFFFC000 
        tempX |= temp2  ''knock out data ready bits
        temp := 0
  
        ''getY
        repeat while temp <> 1  ''temp is a byte, temp2 and tempX are words
              temp := i2cObject.readLocation(bmaddress, ACCYLSB) & $1      ''check data ready bit
        tempymsb := i2cObject.readLocation(bmaddress, ACCYMSB)
        temp2 := tempymsb << 8  ''move MSB to position
        temp2 |= i2cObject.readLocation(bmaddress, ACCYLSB)
        temp2 := temp2 >> 2
        if tempymsb > $7F
          tempY := $FFFFC000 
        tempY |= temp2  ''knock out data ready bits
        temp := 0
        '' get z
        repeat while temp <> 1  ''temp is a byte, temp2 and tempX are words
          temp := i2cObject.readLocation(bmaddress, ACCZLSB) & $1      ''check data ready bit
        tempzmsb := i2cObject.readLocation(bmaddress, ACCZMSB)
        temp2 := tempzmsb << 8  ''move MSB to position
        temp2 |= i2cObject.readLocation(bmaddress, ACCZLSB)
        temp2 := temp2 >> 2
        if tempzmsb > $7F
          tempZ := $FFFFC000 
        tempZ |= temp2  ''knock out data ready bits
        'ser.clear
        'ser.dec(tempz)
        temp := 0
    
          ''gettotals
      totalx := totalx - readingsx[index]    ''subtract previous reading
      totaly := totaly - readingsy[index]
      totalz := totalz - readingsz[index]
      readingsx[index] := tempX     ''put new reading in array
      readingsy[index] := tempY
      readingsz[index] := tempZ
      totalx += readingsx[index]    ''add newest readings to totals
      totaly += readingsy[index]
      totalz += readingsz[index]
      'ser.newline
      'ser.dec(tempZ)
      ''getAvg
      avg_x := totalx / numreadings - 1
      avg_y := totaly / numreadings - 1
      avg_z := totalz / numreadings - 1

      ''get averages before wiping them and make them absolute
      'lastx := avg_x
      'lasty := avg_y
      'lastz := avg_z
      f32.start
      tempx := f32.ffloat(avg_x)     'make true floats out of our variables using averages
      devx := f32.fmul(lsb,tempx)
      tempy := f32.ffloat(avg_y)
      devy := f32.fmul(lsb,tempy)
      tempz := f32.ffloat(avg_z)
      devz := f32.fmul(lsb,tempz)
      ''calculate pitch roll and yaw  - pitch - arctan(ax/sqrt(ay^2+az^2))
      tempx := f32.fmul(devy,devy)
      tempy := f32.fmul(devz,devz)
      tempx := f32.fadd(tempx, tempy)
      tempx := f32.fsqr(tempx)
      tempx := f32.fdiv(devx, tempx)
      pitch[index] := f32.atan(tempx)
      pitch[index] := f32.degrees(devx)  ''end of pitch
      ''roll    arctan(ay/sqrt(ax^2+az^2)
      tempy := f32.fmul(devx,devx)
      tempx := f32.fmul(devz,devz)
      tempy := f32.fadd(tempx, tempy)
      tempy := f32.fsqr(tempy)
      tempy := f32.fdiv(devy, tempy)
      roll[index] := f32.atan(tempy)
      roll[index]:= f32.degrees(devy)  ''end of roll
      '' theta - arctan(sqrt(ax^2+ay^2)/az)
      tempx := f32.fmul(devx, devx)
      tempy := f32.fmul(devy, devy)
      tempz := f32.fadd(tempx, tempy)
      tempz := f32.fdiv(tempz, devz)
      theta[index] := f32.fsqr(tempz)
      theta[index] := f32.atan(theta[index])
      theta[index] := f32.degrees(theta[index])
      f32.stop
      'outa[led] := 0       
      ''alarmcheck
      showall
      'debug      
      index := index + 1
      tempX := 0
      tempY := 0
      tempZ := 0

PUB debug
  repeat index from 0 to numreadings - 1
    Ser.str(String("X : "))
    Ser.dec(readingsx[index])
    Ser.str(String(" Y : "))
    Ser.dec(readingsy[index])
    Ser.str(String(" Z : "))
    Ser.dec(readingsz[index])
    Ser.str(String(" ID : "))
    Ser.dec(index)
    Ser.newline

PUB alarmcheck  'pitch roll and theta are arrays, you can compare throughout
'trying to run this in its own cog
 repeat
    outa[led] := 1
    waitcnt(clkfreq + cnt)  ''set bw
    outa[led] := 0
    waitcnt(clkfreq + cnt)  ''set bw
  
     
PUB init(range, bw)  ''init bma180
  ''if(i2cObject.readLocation(bmaddress,CHIPID) <> 3)
  ''  return -1
  '' set ee_w bit
  temp := i2cObject.readLocation(bmaddress, CTRLREG0)
  temp |= $10
  i2cObject.writeLocation(bmaddress, CTRLREG0, temp)
  waitcnt(clkfreq/10 + cnt)  ''set bw
  temp := i2cObject.readLocation(bmaddress, BWTCS)
  temp1 := bw
  temp1 := (temp1<<4)
  temp &= (!BWMASK)
  temp |= temp1
  i2cObject.writeLocation(bmaddress, BWTCS, temp) ''write new data range, leave other bits the same
  waitcnt(clkfreq/10 + cnt)
  ''set range
  temp := i2cObject.readLocation(bmaddress, OLSB1)
  temp1 := range
  temp1 := (temp1<<RANGESHIFT)
  temp &= (!RANGEMASK)
  temp |= temp1
  i2cObject.writeLocation(bmaddress, OLSB1, temp) ''write new data range, leave other bits the same
  waitcnt(clkfreq/10 + cnt)
  '' turn on slope int 
  temp := i2cObject.readLocation(bmaddress, CTRLREG3)
  temp |= $44
  i2cObject.writeLocation(bmaddress, CTRLREG3, temp)
  ''i2cObject.writeLocation(bmaddress, SLOPETH, $FF)  ''100 threshold
  ''i2cObject.writeLocation(bmaddress, SLOPETAPSENSINFO, $F0) ''XYZ WILL TRIGGER
  ''temp := i2cObject.readLocation(bmaddress, TCOX)
  ''temp |= $3
  ''i2cObject.writeLocation(bmaddress, TCOX, temp) ''slope dur set to 7 readings  
  waitcnt(clkfreq/10 + cnt)
  return 0
  
PUB ReadTemp
  temp := i2cObject.readLocation(bmaddress, TEMPERATURE)
  temptemp := (temp/2+15)*9/5+32             
                       
PUB showall
  Ser.clear
  Ser.str(String(" X: "))
  Ser.str(fstring.floattostring(pitch[index]))
  Ser.str(String(" "))
  Ser.str(String("Y: "))
  Ser.str(fstring.floattostring(roll[index]))
  Ser.str(String(" "))
  Ser.str(String("Z: "))
  Ser.str(fstring.floattostring(theta[index]))
  'Ser.str(String(" Temp:" ))
  'Ser.dec(temptemp) 

PUB setAlarm

PUB startup
  ''take count or do x number of loops
  ''wait a while to let things stabilize.  put it is a variable to allow pin entry post stabilization
  index := 0
  repeat index from 0 to numreadings - 1
    Ser.str(String(" init "))
    readingsx[index] := 0
    readingsy[index] := 0
    readingsz[index] := 0
    pitch[index] := 0
    roll[index] := 0
    theta[index] :=0

I have followed the examples from the manual and I cannot run alarmcheck and main at the same time. Sorry about all the extra comments and probably a lack of good comments.

seiko99 · 2012-08-11 14:17

ok, I got it to work, I told the cognew command to start main and then called alarmcheck. Still don't get why it wouldn't work before

JLocke · 2012-08-11 19:02

It appears that in 'start' you set the direction of the 'led' pin. But you don't set the direction of the pin in 'alarmcheck'. Each cog has its own DIR register and has to be set independently. Try moving 'dira[led] := 1 out of the 'start' method and into the 'alarmcheck' method.

seiko99 · 2012-08-11 20:15

That I didn't try. It works. The manual is a little weak on this fact. The loose references in the coginit chapter point to it, but I pulled several hairs out.
Thank you. Your profile pic leads me to think you are a tesla fan. Am I correct? I am in Victoria just south of you.

flipborder · 2012-09-30 09:24

seiko,

did you ever get your spin code working for the BMA180? I just ordered one and it'd be great if I could use your code to take some readings!

bma180 accelerometer with I2C

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