Using a QMC5883L 3 axis compass sensor – 50 days old

[basparky]

Hi,

I bought a 3 axis compas magnetometer sensor and would like to use it in a project.

The sensor is mounted on a breakout board See:http://wiki.sunfounder.cc/index.php?title=QMC5883L

I have connected the board to a dspic33FJ128MC706A with the pullups on the sda and scl lines. There is also an external eeprom connected to these lines which functions as expected.

Following the datasheet https://www.tinytronics.nl/shop/image/data/Producten/Sensoren/Magnetisch veld/Datasheet-QMC5883L-1.0 .pdf
it tells me on page 13 the registers i need to setup.
I made:

Proc InitCompass()BStart
BusOut 011010
BusOut 0xB
BusOut 0x01
BStop


BStart
BusOut 011010
BusOut 0x9
BusOut 0x1D
BStop


BusOut 011010
BusOut 0xA
BusOut 0x80
BStop
DelayMS 5


EndProc

Following this datasheet on page 15 it tells me how to write and read.

I thought by doing above for writing the config registers and this for reading the data registers i would be able to get some data from the module...

BStart BusOut 011010,[0x00]
DelayMS 1
BStart
BusIn 011011,[0x00]
BusIn XCom1
BusAck
BusIn XCom2
BStop

This doesnt give any results.

Does anyone has some experience with this compass sensor?

Thanks for any help!

[basparky]

Got it working!
Different approach as above with success:
At startup i do:

Proc InitCompass()    
    BusOut 011010, 0xB,[0x01]        'Set reset period, Datasheet page 13 for application example.
    DelayMS 5
    BusOut 011010, 0x9,[000001]   'Continuous measurement mode
EndProc

then i read every 100ms the first 6 registers. Datasheet page 16 and calculate the heading:

Proc GetCompass()     
     BusIn  011011,0x00,[XCom.LowByte,XCom.HighByte, YCom.LowByte,YCom.HighByte,ZCom.LowByte,ZCom.HighByte]
     Heading = ReadHeading()
EndProc

Proc ReadHeading(),WordDim x As SWord
Dim y As SWord
Dim fx As Float
Dim fy As Float
Dim Heading As SWord
Dim DeclinationAngle As Float


    If XCom < Xlow Then Xlow = XCom
    If XCom > XHigh Then XHigh = XCom
    If YCom < Ylow Then Ylow = YCom
    If YCom >YHigh Then YHigh = YCom
    
    If Xlow = XHigh Or Ylow = YHigh Then 
        Heading = 0
        Result = 0
        Return
    EndIf
    
    DeclinationAngle = (1 + (56/60))/(180/pi)  'For Grootebroek in the Netherlands;)
    
    x = XCom - (XHigh + Xlow) /2
    y = YCom - (YHigh + Ylow) /2
    
    fx = x/(XHigh - Xlow)
    fy = y/(YHigh - Ylow)
        
    Heading = 180 * ATan2( fy,fx)/ Pi
    Heading = Heading - 80 ; Somehow i need to correct with -80 (compared to telephone compass which looks ok).   
    If Heading <=0 Then Heading = Heading + 360
    
    HRSOut "Xcom= ",SDec XCom," xlow= ",SDec Xlow," xhigh=",Dec XHigh," x= ",SDec x," fx= ",SDec fx," Heading= ",Dec Heading ,"DeclinationAngle= ",SDec DeclinationAngle,"\r\n"
    
Result = Heading


EndProc

There is a huge error from +80 for the calculated heading which i still need to fix somehow..

[top204]

Excellent code! Proton makes it look so easy, even though it is not. :-)

Make sure you are converting degrees to radians for the compiler's trig procedures, and back again for viewing etc...

I've been caught out like that in the past, when I forgot to convert, or didn't get the divisions etc in the correct place. LOL

I can see a 180 and 360 values and Pi in the code, so make sure they are in the correct positions for radian/degrees conversions etc...

[david]

Proton certainly makes OUR code look easy and there are times when I think it's ridiculously concise compared to other languages.
I've not used the QMC5883L (Chinese knock-off) but have used the original Honeywell HMC5883. The two are almost identical with only some minor changes in the config set up.

This is what I used to read the bare sensor values of the HMC5883-

Declare Hbus_Bitrate 100 '100kHz or 400kHz


'************* I2C comms set up **************************************
SSPCON1=%00111000 'enable port, 7 bit address, master mode


'*********** Set up *********************
Symbol MAG_W= %11110000 'Device address and write
Symbol MAG_R= %11110001 'Device address and read 7 6 5 4 3 2 1 0


'********** ADC variables ******************
Dim MAGX As Word
Dim MAGY As Word
Dim MAGZ As Word


'initialize
HBusOut MAG_W,[0,112] 'Write, Reg 0, 112 112=8avg, 15Hz rate
HBusOut MAG_W,[1,160] 'Write, Reg 1, Gain 5


begin:
HBusOut MAG_W,[2,1] 'Write, Reg 2, Single shot mode
DelayMS 10 'pointer auto increments
HBusIn MAG_R,[MAGX, MAGY, MAGZ] 'returns 16 bit value of 3 mag axis



'*************** output data ****************************


HRSOut "X=",Dec MAGX," ","Y=",Dec MAGY, " ","Z=",Dec MAGZ,13 '9600 direct - no inverter.
DelayMS 500
GoTo begin

If you take away the comments there's not much left. Proton really is a work of art.

Cheers,
David

[top204]

I've just noticed your code is:

Proc ReadHeading(),WordDim x As SWord

I know this is a forum thread issue that has removed a carriage return from the line, so I'll just alter it for other users. It should have read:

Proc ReadHeading(),Word

Dim x As SWord

Again.... Excellent code from basparky and David. It is such a good feeling when people with skills and knowledge are using a language I created and finding it useful. :-)

[flosigud]

A HMC5883L library that I adapted from somewhere.

'    ----------------------------------------------------------------------------'    Name    : HMC5883L.INC                                      
'    Author  : Flosi Guðmundsson                                                          
'    Date    : 24.10.2020                                        
'    Version : 1.0                                               
'    Notes   :                                                   
'            :                                                   
'    ----------------------------------------------------------------------------




'    HMC5883L_init
'    Float = GetHeading




'
'    HMC5883 registers
'    ----------------------------------------------------------------------------
'
    Symbol HMC5883_CRA_REG            = 0        ' Configuration_Register_A
    Symbol HMC5883_CRB_REG            = 1        ' Configuration_Register_B
    Symbol HMC5883_MR_REG            = 2        ' Mode_Register
    Symbol HMC5883_OUT_X_H            = 3        ' Data_Output_X_MSB_Register
    Symbol HMC5883_OUT_X_L            = 4        ' Data_Output_X_LSB_Register
    Symbol HMC5883_OUT_Z_H            = 5        ' Data_Output_Z_MSB_Register
    Symbol HMC5883_OUT_Z_L            = 6        ' Data_Output_Z_LSB_Register
    Symbol HMC5883_OUT_Y_H            = 7        ' Data_Output_Y_LSB_Register
    Symbol HMC5883_OUT_Y_L            = 8        ' Data_Output_Y_MSB_Register
    Symbol HMC5883_SR_REG            = 9        ' Status_Register_Read
    Symbol HMC5883_IRA_REG            = 10    ' Identification_Register_A
    Symbol HMC5883_IRB_REG            = 11    ' Identification_Register_B
    Symbol HMC5883_IRC_REG            = 12    ' Identification_Register_C
    Symbol HMC5883_TEMP_OUT_H        = $31    '
    Symbol HMC5883_TEMP_OUT_L        = $32    '


    
    Symbol X_MSB = $03                         ' Read Register, Output of swXaxis MSB 8-bit value.
    Symbol X_LSB = $04                        ' Read Register, Output of swXaxis LSB 8-bit value.
    Symbol Z_MSB = $05                        ' Read Register, Output of swZaxis MSB 8-bit value.
    Symbol Z_LSB = $06                        ' Read Register, Output of swZaxis LSB 8-bit value.
    Symbol Y_MSB = $07                        ' Read Register, Output of swYaxis MSB 8-bit value.
    Symbol Y_LSB = $08                        ' Read Register, Output of swYaxis LSB 8-bit value.


    Symbol WRITE_ADDRESS = $3C                ' Requests Write operation
    Symbol READ_ADDRESS = $3D                ' Requests Read operation
    Symbol MODE = $02                        ' Mode setting register
    Symbol Pi = 3.141592654
    Symbol Pi2 = 6.283185307
   
    Symbol DeclinationAngle = -13.233333333333333/57.295779
    
'
'    HMC5883L_init()
'    ----------------------------------------------------------------------------
'
    $define HMC5883L_init _HMC5883L_init    
    Proc _HMC5883L_init()
'        Global Dim swXaxis As SWord                        ' swXaxis sensor measured value
'        Global Dim swYaxis As SWord                        ' swYaxis sensor measured value
'        Global Dim swZaxis As SWord                        ' swZaxis sensor measured value
    
        Global Dim Heading As Float
        HBusOut WRITE_ADDRESS, HMC5883_CRA_REG, [$70]    ' (8-average, 15 Hz default, normal measurement)
        HBusOut WRITE_ADDRESS, HMC5883_CRB_REG, [$A0]    ' Gain=5
        HBusOut WRITE_ADDRESS, HMC5883_MR_REG, [$00]    ' Send continuous output command
    EndProc


' 
'    GetHeading()
'    ----------------------------------------------------------------------------
'
    $define GetHeading _GetHeading
    Proc _GetHeading(), Float
        HBusIn READ_ADDRESS, $03, [swXaxis.HighByte, swXaxis.LowByte, swZaxis.HighByte, swZaxis.LowByte, swYaxis.HighByte, swYaxis.LowByte]
        Dim fXaxis As Float = swXaxis                    ' Convert the numbers to Float
        Dim fYaxis As Float = swYaxis                    ' Else Result will be garbage
        Dim swXaxis As SWord                            ' swXaxis sensor measured value
        Dim swYaxis As SWord                            ' swYaxis sensor measured value
        Dim swZaxis As SWord                            ' swZaxis sensor measured value
        Result = ATan2(fYaxis, fXaxis)                    ' Calculate the ATan2
        Result = Result + DeclinationAngle                ' DeclinationAngle is different in every place
        If Result < 0 Then Result = Result + Pi2        ' Add 2 * Pi
        If Result > Pi2 Then Result = Result - Pi2        ' Subtract 2 * Pi
        Result = Result * 57.295779                        ' Convert radians to degrees
    EndProc

This is how I use it.

'    ----------------------------------------------------------------------------'    Name    : HMC5883L_demo.BAS                                      
'    Author  : Flosi Guðmundsson                                           
'            : All Rights Reserved                               
'    Date    : 10.7.2020                                         
'    Version : 1.0                                               
'    Notes   :                                                   
'            :                                                   
'    ----------------------------------------------------------------------------


'    Include "..\..\33fj128GP802.inc"
    Include "..\..\33FJ12MC202.inc"
'    Include "..\..\..\33FJ32MC302.inc"


'    ----------------------------------------------------------------------------


    Include "HMC5883L.Inc"




    HMC5883L_init()
    DelayMS 200
    Do
        Heading = GetHeading()
        HRSOut "Heading : ",Dec Heading," N   ",13
        DelayMS 200
    Loop 
    
'    ----------------------------------------------------------------------------

[basparky]

Hi,

I noticed the following:
If i use:

     
Dim wHeading as Sword

If wHeading < -90 Then wHeading = -90
If wHeading > 90 Then wHeading = 90

wHeading is always -90

If i use:

     
Dim MinH As SWordMinH = -90
If wHeading < MinH Then wHeading = -90
If wHeading > 90 Then wHeading = 90

It works as expected.

Is this my mistake?

[top204]

I've just ran a test on an 18F device and an enhanced 14-bit core device and the comparison is working as expected. With this code snippet:

    Dim wHeading As SWord

    wHeading = -100
    If wHeading < -90 Then
        HRSOutLn "Less Than"
    Else
        HRSOutLn "Greater or Equal"
    EndIf

It transmits the corrects texts for the correct comparison depending on what value is loaded into wHeading

[basparky]

Thanks for your time.

If i test the following in a dsPic33FJ32MC204 i always get the value -90 as result. Doenst matter what value i put in ActualHeading..

Dim ActualHeading As SWord


ActualHeading = 500
If ActualHeading < -90 Then ActualHeading = -90
If ActualHeading > 90 Then ActualHeading = 90 


HRSOut SDec ActualHeading,"\r\n"

If i use your code with the value 500 in wHeading i also get "Less than" as result

If is use the following it works as i thought it should and gives me as result "Greater or Equal"

    Dim wHeading As SWord
    Dim Value As SWord
    Value = -90
    wHeading = 500
    If wHeading < Value Then
        HRSOutLn "Less Than"
    Else
        HRSOutLn "Greater or Equal"
    EndIf

[top204]

This is in the Proton ver 3 section of the forum, so I automatically assumed it was a possible anomaly with an 8-bit device!

I'll check out Proton24 now.

[basparky]

Sorry! did not realize i was in the wrong section

[top204]

There is an anomaly in Proton24 for this comparison. The compiler is producing the negative constant value as 32-bit within its source, so it does not see the values correctly when negative.

Change the variable "ActualHeading" to an SDword type and the comparison works as expected.

I've now corrected the anomaly and looked for any more that may cause the issue with negetive constants on Byte and Word comparisons and will have an update for the anomaly fix ASAP.

Thanks for spotting that obscure anomaly. :-)