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Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
Recently I'm designing an IMU for a multicopter starting from the basics but I will soon add also altimeter (already implemented) and GPS
The module i use is the AltIMU-10 v4, comprising of: LSM303D - 3d accelerometer and 3d magnetometer L3GD20H - 3d electronic rate gyroscope LPS25H - Pressure sensor for altitude
I already designed all the mathematical routines to handle these data, in particular based on quaternion and vector calculations, along with fast CORDIC-like trigonometry
The communication between the module and the PIC is made by I2C
I'm able to setup, and read correctly the gyroscope (L3GD20H), magnetometer (LSM303D) and the altimeter (LPS25H), but I have no luck with the accelerometer (L3GD20H)
It simply gives random values centered around 24444 (two modules) or 33000 (the other two). The registers are read and written correctly but no meaningful value comes from the accelerometer.... I exclude module malfunction since I tried 4 of them, coming from different sources.
Without the accelerometer I'm unable to correct the gyro drift in the complementary filter....
MEMS communication subroutines:
'****************************************************************
'* Name : MEMS-IMU.BAS *
'* Author : Jonathan FIlippi *
'* Notice : Copyright (c) 2014 CC free license *
'* : All Rights Reserved *
'* Date : 22/9/2014 *
'* Version : 1.0 *
'* Notes : MEMS I2C communication, RAW data transformation *
'* : *
'****************************************************************
'****************************************************************
'*** VARIABLE DECLARATIONS ***
'****************************************************************
M_w1 var word
M_w2 var word
M_s0 var byte
M_s1 var byte
M_s2 var byte
M_b var byte[6]
M_l0 var LONG 'signed
M_l1 var LONG 'signed
M_Accel_RAW var WORD[3] 'vector
M_Magn_RAW var WORD[3] 'vector
M_Gyro_RAW var WORD[3] 'vector
M_Gyro_RAW_OFFSET var LONG[3] 'vector
M_Accel var long[3] 'vector
M_Magn var long[3] 'vector
M_Gyro var long[3] 'vector
M_Altimeter_RAW var LONG
M_Altimeter var LONG
SLAVE_ADDR var byte
ADDR var byte
VALUE var byte
'****************************************************************
'*** ALIASES ***
'****************************************************************
' SLAVE addresses
Symbol MEMS_MagnetAccel_R = %00111011 'SA0 High
Symbol MEMS_MagnetAccel_W = %00111010 'SA0 High
Symbol MEMS_Gyro_R = %11010111 'SA0 High
Symbol MEMS_Gyro_W = %11010110 'SA0 High
Symbol MEMS_Altimeter_R = %10111011 'SA0 High
Symbol MEMS_Altimeter_W = %10111010 'SA0 High
' Generic symbols
Symbol GX = 0
Symbol GY = 1
Symbol GZ = 2
Symbol WHO_AM_I = $0F
' gyro sub-addresses
Symbol GYRO_CTRL1 = $20
Symbol GYRO_CTRL2 = $21
Symbol GYRO_CTRL3 = $22
Symbol GYRO_CTRL4 = $23
Symbol GYRO_CTRL5 = $24
Symbol GYRO_OUT_X_L = $28
Symbol GYRO_OUT_X_H = $29
Symbol GYRO_OUT_Y_L = $2A
Symbol GYRO_OUT_Y_H = $2B
Symbol GYRO_OUT_Z_L = $2C
Symbol GYRO_OUT_Z_H = $2D
Symbol GYRO_LOW_ODR = $39
' accel and magnetometer sub-addresses
Symbol ACCEL_CTRL0 = $1F
Symbol ACCEL_CTRL1 = $20
Symbol ACCEL_CTRL2 = $21
Symbol ACCEL_CTRL3 = $22
Symbol ACCEL_CTRL4 = $23
Symbol ACCEL_CTRL5 = $24
Symbol ACCEL_CTRL6 = $25
Symbol ACCEL_CTRL7 = $26
Symbol ACCEL_OUT_X_L = $28
Symbol ACCEL_OUT_X_H = $29
Symbol ACCEL_OUT_Y_L = $2A
Symbol ACCEL_OUT_Y_H = $2B
Symbol ACCEL_OUT_Z_L = $2C
Symbol ACCEL_OUT_Z_H = $2D
Symbol MAGN_OUT_X_L = $08
Symbol MAGN_OUT_X_H = $09
Symbol MAGN_OUT_Y_L = $0A
Symbol MAGN_OUT_Y_H = $0B
Symbol MAGN_OUT_Z_L = $0C
Symbol MAGN_OUT_Z_H = $0D
' altimeter sub-addresses
Symbol ALTIMETER_RES_CONF = $10
Symbol ALTIMETER_CTRL1 = $20
Symbol ALTIMETER_CTRL2 = $21
Symbol ALTIMETER_CTRL3 = $22
Symbol ALTIMETER_CTRL4 = $23
Symbol ALTIMETER_OUT_XL = $28
Symbol ALTIMETER_OUT_L = $29
Symbol ALTIMETER_OUT_H = $2A
Symbol ALTIMETER_REF_XL = $08
Symbol ALTIMETER_REF_L = $09
Symbol ALTIMETER_REF_H = $0A
'gyro configuration
Symbol GYRO_SENSITIVITY = 2294 '0.07 dps/s/LSB
Symbol GYRO_SENS_DIVIDER = 1 '0.07 dps/s/LSB
Symbol GYRO_2SCOMPLEMENT_MAX = $FFFF
Symbol GYRO_CTRL1_VALUE = %00001111 'DR1-DR0 = 00/BW1-BW0 = 00/PD = 1/
'Zen = 1/Yen = 1/Zen = 1 , data rate 100Hz
Symbol GYRO_CTRL2_VALUE = %00100011 'EXTRen = 0/LVRen = 0/HPM1-HPM0 = 00/ 'high pass filter normal
'HPCF3-HPCF0 = 0011 ' 1 Hz High pass filter cut off freq
Symbol GYRO_CTRL3_VALUE = %00000000 'INT1-IG = 0/INT1-BOOT = 0/H_LACTIVE = 0/PP_OD = 1
'INT2_DRDY = 0/INT2_FTH = 0/INT2_ORun = 0/INT2_Empty = 0
Symbol GYRO_CTRL4_VALUE = %10100000 'BDU = 1/BLE = 0/FS1-FS0 = 10/IMPen = 0/ST2-ST1 = 00/ SIM = 0
'2000 dps full scale
Symbol GYRO_CTRL5_VALUE = %00010000 'BOOT = 0/FIFO_EN = 0/StopOnFTH = 0/HPen = 1/IG_Sel1-IGSel0 = 00
'OUTG_Sel1-OUTGSel0 = 00
Symbol GYRO_LOW_ODR_VALUE = %00000000 '-/-/DRDY_HL = 0/-/I2C_dis = 0/SW_RES = 0/LOW_ODR = 0
'accel & magnetometer configuration
Symbol ACCEL_SENSITIVITY = 3998 '0.122 mG/LSB
Symbol ACCEL_2SCOMPLEMENT_MAX = $FFFF
Symbol MAGN_2SCOMPLEMENT_MAX = $FFFF
symbol MAGN_SENSITIVITY = 5243 ' 0.160 mgauss / LSB
Symbol ACCEL_CTRL0_VALUE = %00000000 'BOOT = 0/FIFO_EN = 0/FTH_EN = 0/0/0/HP_Click = 0/HPIS1 = 0/HPIS2 = 0
Symbol ACCEL_CTRL1_VALUE = %01101111 'ADDR3-ADDR0 = 0000/DBU = 1/AZEN = 1/AYEN = 1/AXEN = 1
' 100 Hz data rate, all channels elabled
Symbol ACCEL_CTRL2_VALUE = %00001000 'ABW1-ABW0 = 00/AFS2-AFS0 = 001/0/AST = 0/SIM = 0
'50 Hz filter bandwith , 4g sensitivity
Symbol ACCEL_CTRL3_VALUE = %00000000 'INT1_BOOT = 0/INT1_Click = 0/INT1_IG1 = 0/INT1_IG2 = 0/INT1_IGM = 0
'INT1_DRDY_M = 0/INT1_DRDY_M = 0/INT1_EMPTY = 0
Symbol ACCEL_CTRL4_VALUE = %00000000 'All interrupts disabled
Symbol ACCEL_CTRL5_VALUE = %11110100 'TEMP_EN = 1/M_RES1-M_RES0 = 11/M_ODR2-M_ODR0 = 101/ IRQ non latched
'100Hz magnetometer data rate
Symbol ACCEL_CTRL6_VALUE = %00100000 'MFS1-MFS= 10 magnetic full scale set to 4gauss
Symbol ACCEL_CTRL7_VALUE = %00000000 'AHPM1-AHPM0 = 00/AFDS = 0/T_ONLY = 0/MLP = 0/MD1-MD0 = 00
'altimeter configuration
Symbol ALTIMETER_SENSITIVITY = 8 '4096 LSB = 1hPa
Symbol ALTIMETER_2SCOMPLEMENT_MAX = $FFFFFF
Symbol ALTIMETER_RES_CONF_VALUE = %00001111 'Reserved/AVGT1 = 1/AVGT0 = 1/AVGP1 = 1/AVGP0 = 1
Symbol ALTIMETER_CTRL1_VALUE = %11000100 'PD = 1 / ODR2-ODR0 = 100 / DIFF_EN = 0 / BDU = 1 / RESET_AZ = 0 / SIM = 0
Symbol ALTIMETER_CTRL2_VALUE = %00000000 'BOOT = 0 / FIFO_EN = 0 / WTM_EN = 0 / FIFO_MEAN_DEC = 0 / SWRESET = 0 / AUTO_ZERO = 0 / ONE_SHOT = 0
Symbol ALTIMETER_CTRL3_VALUE = %00000000 'INT_H_L = 0 / PP_OD = 0/ Reserved / INT1_S2-INT1_S1 = 00
Symbol ALTIMETER_CTRL4_VALUE = %00000000 '0/0/0/0/ P1_EMPTY = 0/ P1_WTM = 0 / P1_Overrun = 0 / P1_DRDY = 0
' pin assignements
SYMBOL I2C_DATAPIN = PORTB.1 ' data assigned to PORTB.1
SYMBOL I2C_CLOCKPIN = PORTB.0 ' clock assigned to PORTB.0
'****************************************************************
'*** I/O PORT ASSIGNMENTS ***
'****************************************************************
TRISB.1 = 0
TRISB.0 = 0
goto Q_skipmems:
'******************************************************************************
'********** M_READGYRO_RAW -> vector M_Gyro_RAW[WORD]
'********** this subroutine reads the on-board IMU gyroscope
'**********
'******************************************************************************
M_READGYRO_RAW:
SLAVE_ADDR = MEMS_Gyro_W
ADDR = GYRO_CTRL1
value = GYRO_CTRL1_VALUE
gosub M_I2CWRITE:
for M_s1 = 0 to 5
SLAVE_ADDR = MEMS_Gyro_R
ADDR = GYRO_OUT_X_L + M_s1
gosub M_I2CREAD:
M_B[M_s1] = VALUE
next
for M_s1 = 0 to 4 step 2
M_Gyro_RAW[M_s1>>1] = M_b[M_s1+1] << 8 | M_b[M_s1]
next
return
'******************************************************************************
'********** M_READALTIMETER_RAW -> RAM pressure value[LONG]
'********** this subroutine reads the on-board IMU barometric altimeter
'**********
'******************************************************************************
M_READALTIMETER_RAW:
SLAVE_ADDR = MEMS_Altimeter_W
ADDR = Altimeter_CTRL1
value = Altimeter_CTRL1_VALUE
gosub M_I2CWRITE:
for M_s1 = 0 to 2
SLAVE_ADDR = MEMS_Altimeter_R
ADDR = Altimeter_OUT_XL + M_s1
gosub M_I2CREAD:
M_B[M_s1] = VALUE
next
M_Altimeter_Raw = ((M_B[2] << 8 + M_B[1]) << 8) + M_B[0]
return
'******************************************************************************
'********** M_READALTIMETER -> pressure value[LONG] (hPa)
'********** this subroutine reads the on-board IMU barometric altimeter
'**********
'******************************************************************************
M_READALTIMETER:
gosub M_READALTIMETER_RAW:
if M_Gyro_RAW[M_s1] > altimeter_2SCOMPLEMENT_MAX >> 1 then ' sign negative 2's complement value
M_l1 = (altimeter_2SCOMPLEMENT_MAX - M_altimeter_RAW) * ALTIMETER_SENSITIVITY
else
M_l1 = M_Altimeter_Raw * ALTIMETER_SENSITIVITY
endif
'average of 16 values
if m_altimeter = 0 then
M_Altimeter = M_l1
else
M_Altimeter = ( M_Altimeter << 4 - M_Altimeter + M_l1 ) >> 4
endif
return
'******************************************************************************
'********** M_READGYRO -> vector M_Gyro[LONG] , angle rate in mdegrees/s
'********** this subroutine reads the on-board IMU gyroscope
'**********
'******************************************************************************
M_READGYRO:
gosub M_READGYRO_RAW:
for M_s1 = 0 to 2
if M_Gyro_RAW[M_s1] > GYRO_2SCOMPLEMENT_MAX >> 1 then ' sign negative 2's complement value
M_Gyro[M_s1] = (-(GYRO_2SCOMPLEMENT_MAX - M_Gyro_RAW[M_s1]) - M_Gyro_RAW_OFFSET[M_s1]) * GYRO_SENSITIVITY / GYRO_SENS_DIVIDER
else
M_Gyro[M_s1] = (M_Gyro_RAW[M_s1] - M_Gyro_RAW_OFFSET[M_s1]) * GYRO_SENSITIVITY / GYRO_SENS_DIVIDER
endif
next
return
'******************************************************************************
'********** M_CONFIGGYRO
'********** configurates the Gyroscope device
'**********
'******************************************************************************
M_CONFIGGYRO:
SLAVE_ADDR = MEMS_Gyro_W
ADDR = GYRO_CTRL1
value = GYRO_CTRL1_VALUE
gosub M_I2CWRITE:
ADDR = GYRO_CTRL2
value = GYRO_CTRL2_VALUE
gosub M_I2CWRITE:
ADDR = GYRO_CTRL3
value = GYRO_CTRL3_VALUE
gosub M_I2CWRITE:
ADDR = GYRO_CTRL4
value = GYRO_CTRL4_VALUE
gosub M_I2CWRITE:
ADDR = GYRO_CTRL5
value = GYRO_CTRL5_VALUE
gosub M_I2CWRITE:
ADDR = GYRO_LOW_ODR
value = GYRO_LOW_ODR_VALUE
gosub M_I2CWRITE:
gosub M_READGYRO:
return
'******************************************************************************
'********** M_CONFIGALTIMETER
'********** configurates the barometric altimeter
'**********
'******************************************************************************
M_CONFIGALTIMETER:
SLAVE_ADDR = MEMS_ALTIMETER_W
ADDR = ALTIMETER_CTRL1
value = ALTIMETER_CTRL1_VALUE
gosub M_I2CWRITE:
ADDR = ALTIMETER_CTRL2
value = ALTIMETER_CTRL2_VALUE
gosub M_I2CWRITE:
SLAVE_ADDR = MEMS_ALTIMETER_R
ADDR = ALTIMETER_RES_CONF
gosub M_I2CREAD:
M_s1 = value >> 4
VALUE = M_s1 << 4 + ALTIMETER_RES_CONF_VALUE
SLAVE_ADDR = MEMS_ALTIMETER_W
ADDR = ALTIMETER_RES_CONF
gosub M_I2CWRITE:
M_Altimeter = 0
return
'******************************************************************************
'********** M_CONFIGGYRO
'********** calculates the gyroscope offset
'**********
'******************************************************************************
M_CONFIGGYROOFFSET:
' offset calibration
for M_s0 = 0 to 2
M_Gyro_RAW_OFFSET[M_s0] = 0
for M_s2 = 0 to $FF
gosub M_READGYRO_RAW:
M_Gyro_RAW_OFFSET[M_s0] = M_Gyro_RAW_OFFSET[M_s0] + M_Gyro_RAW[M_s0]
pause 2
next M_s2
M_Gyro_RAW_OFFSET[M_s0] = M_Gyro_RAW_OFFSET[M_s0] >> 8
if M_Gyro_RAW_OFFSET[M_s0] > GYRO_2SCOMPLEMENT_MAX >> 1 then ' sign negative 2's complement value
M_Gyro_RAW_OFFSET[M_s0] = -(GYRO_2SCOMPLEMENT_MAX - M_Gyro_RAW[M_s0])
else
M_Gyro_RAW_OFFSET[M_s0] = (M_Gyro_RAW[M_s0] )
endif
next M_s0
return
'******************************************************************************
'********** M_READACCEL_RAW -> vector M_Accel_RAW[WORD]
'********** this subroutine reads the on-board IMU accelerometer
'**********
'******************************************************************************
M_READACCEL_RAW:
'SLAVE_ADDR = MEMS_MagnetAccel_W
' ADDR = ACCEL_CTRL0
'value = ACCEL_CTRL0_VALUE
'gosub M_I2CWRITE:
for M_s1 = 0 to 5
SLAVE_ADDR = MEMS_MagnetAccel_R
ADDR = ACCEL_OUT_X_L + M_s1
gosub M_I2CREAD:
M_B[M_s1] = VALUE
next
for M_s1 = 0 to 4 step 2
M_Accel_RAW[M_s1>>1] = M_b[M_s1+1] << 8 | M_b[M_s1]
next
return
'******************************************************************************
'********** M_READACCEL -> vector M_Accel[LONG] , acceleration in g
'********** this subroutine reads the on-board IMU accelerometer
'**********
'******************************************************************************
M_READACCEL:
gosub M_READACCEL_RAW:
for M_s1 = 0 to 2
if M_Accel_RAW[M_s1] > ACCEL_2SCOMPLEMENT_MAX >> 1 then ' sign negative 2's complement value
M_Accel[M_s1] = -(ACCEL_2SCOMPLEMENT_MAX - M_Accel_RAW[M_s1]) * ACCEL_SENSITIVITY
else
M_Accel[M_s1] = M_Accel_RAW[M_s1] * ACCEL_SENSITIVITY
endif
next
return
'******************************************************************************
'********** M_READMAGN_RAW -> vector M_Magn_RAW[WORD]
'********** this subroutine reads the on-board IMU accelerometer
'**********
'******************************************************************************
M_READMAGN_RAW:
SLAVE_ADDR = MEMS_MagnetAccel_W
ADDR = ACCEL_CTRL0
value = ACCEL_CTRL0_VALUE
gosub M_I2CWRITE:
for M_s1 = 0 to 5
SLAVE_ADDR = MEMS_MagnetAccel_R
ADDR = MAGN_OUT_X_L + M_s1
gosub M_I2CREAD:
M_B[M_s1] = VALUE
next
for M_s1 = 0 to 4 step 2
M_MAgn_RAW[M_s1/2] = M_b[M_s1+1] << 8 | M_b[M_s1]
next
return
'******************************************************************************
'********** M_READMAGN -> vector M_Magn[LONG] , magnetic axes in gauss
'********** this subroutine reads the on-board IMU accelerometer
'**********
'******************************************************************************
M_READMAGN:
gosub M_READMAGN_RAW:
for M_s1 = 0 to 2
if M_Magn_RAW[M_s1] > 32768 then ' sign negative 2's complement value
M_Magn[M_s1] = -(MAGN_2SCOMPLEMENT_MAX - M_MAGN_RAW[M_s1]) * MAGN_SENSITIVITY
else
M_Magn[M_s1] = M_Magn_RAW[M_s1] * MAGN_SENSITIVITY
endif
next
return
'******************************************************************************
'********** M_CONFIGACCELMAGN
'********** configurates the Accelerometer & Magnetometer device
'**********
'******************************************************************************
M_CONFIGACCELMAGN:
SLAVE_ADDR = MEMS_MagnetAccel_W
ADDR = ACCEL_CTRL0
value = ACCEL_CTRL0_VALUE
gosub M_I2CWRITE:
ADDR = ACCEL_CTRL1
value = ACCEL_CTRL1_VALUE
gosub M_I2CWRITE:
ADDR = ACCEL_CTRL2
value = ACCEL_CTRL2_VALUE
gosub M_I2CWRITE:
ADDR = ACCEL_CTRL3
value = ACCEL_CTRL3_VALUE
gosub M_I2CWRITE:
ADDR = ACCEL_CTRL4
value = ACCEL_CTRL4_VALUE
gosub M_I2CWRITE:
ADDR = ACCEL_CTRL5
value = ACCEL_CTRL5_VALUE
gosub M_I2CWRITE:
ADDR = ACCEL_CTRL6
value = ACCEL_CTRL6_VALUE
gosub M_I2CWRITE:
ADDR = ACCEL_CTRL7
value = ACCEL_CTRL7_VALUE
gosub M_I2CWRITE:
return
'******************************************************************************
'********** M_I2CWRITE
'********** This function writes a byte VALUE into ADDR at the SLAVE_ADDR
'**********
'******************************************************************************
M_I2CWRITE:
I2CWRITE I2C_DATAPIN,I2C_CLOCKPIN,SLAVE_ADDR,ADDR,[VALUE]
return
'******************************************************************************
'********** M_I2CREAD
'********** This function writes a byte VALUE into ADDR at the SLAVE_ADDR
'**********
'******************************************************************************
M_I2CREAD:
I2CREAD I2C_DATAPIN,I2C_CLOCKPIN,SLAVE_ADDR,ADDR,[VALUE]
return
Q_skipmems:
I didn't include the mathematical subroutines since they aren't used yet.
Registered Member #84
Joined: Thu Feb 09 2006, 01:06PM
Location: Dallas, TX
Posts: 47
I have the AltIMU-10 v3 and everything works fine with example program that Pololu provides. Maybe you can use it to verify that your board actually works?
In my application, I used a Teensy 3.0 to log the data to an SD card for my model rocket.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Im so interested in things like this, i even bought some real good accel, gyros, and mags. i just wish i new more about I2C and SPI, i even have a I2C LiDAR.
Registered Member #14
Joined: Thu Feb 02 2006, 01:04PM
Location: Prato/italy
Posts: 383
ACtually I have finished the AHRS part (10-DOF) including the filtering of the gyro data with accelerometer and magnetometer and the determination of global acceleration components to filter the barometric data (it needs some tuning). The filtering is done with a variable gain complementary filter (adjusts the gain depending on how much the accelerometer data is off), i didn't use kalman since it is too slow for this hardware. I have also changed the PIC18f2680 to a PIC18F26k80 running at 64 MHz and moved the I2C bus on the hardware bus increasing the clock frequency to 1MHz, obtaining an imu update rate of 150-180 Hz.
Actually i'm working on the GPS part. I'm able to read it at 10Hz rate but it is very difficult to sinch with the IMU (since there are no background processes in those type of PIC). I want to minimize the time the the USART bus (hardware) waits for the NMEA String since it will ruin the IMU update rate greatly, even if the duty cycle is very low (7%). In optimal conditions, the NMEA string reading takes 7ms every 100ms so it needs very careful sinching by using the hardware clock of the PIC (i'm already using TMR1 driven by PIC instruction clock with a 64 prescale value, each LSB corresponds to 4us).
If the GPS falls out of sinch (and it is very likely since there is also some unpredictable duty cycle devoted to printing the data on an LCD screen) the IMU freezes for 100ms that means instant crash for an UAV :D :D :D
I hate USART ... I2C GPS would be much more useful...
Anyways if the problem cannot be solved I will be forced to add a second PIC to work as a front-end for the GPS, the PPM, D-Bus receiver and the AI, while the core pic will take care only of the IMU and the output to the ESCs taking angle setpoints from the other pic...
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IMU with AltIMU-10 v4
... I2C GPS would be much more useful...