problem with HMC6352 compass

Hello,

I tried to port this code from a BS2, to get it to work on a 16F877A. I am experiencing erratic
behavior. The display flickers terribly and the values are meaingless. What am I missing?

Code:

INCLUDE "Modedefs.Bas" @ Device pic16F877A, HS_OSC, LVP_OFF, WDT_OFF,protect_off DEFINE OSC 20 ; Set port direction and turn off unused peripherals CMCON = 7 ' shut offcomparators TRISA = %00000000 ' Set PORTA to input "1" or output "0" TRISB = %00000000 ' set portB to output "0" or input "1" TRISC = %00000000 TRISD = %00000000 TRISE = %00000000 ; initialize all ports to low portA = %00000000 portB = %00000000 portC = %00000000 portD = %00000000 portE = %00000000 ; define LCD 4 line x 20, 4 bit interface Define LCD_DREG PORTD Define LCD_DBIT 0 Define LCD_RSREG PORTD Define LCD_RSBIT 4 Define LCD_EREG PORTD Define LCD_EBIT 5 Define LCD_BITS 4 Define LCD_LINES 4 define LCD_COMMANDUS 1500 DEFINE LCD_DATAUS 44 'main2: ' Lcdout $fe, 1, $fe, $80 ' Clear LCD screen ' Lcdout $FE, $80, "testing" ' Pause 2000 ' Wait .5 second ' goto main2 ' -----[ Pins/Constants/Variables ]------------------------------------------- SDA VAR portB.0 ' PB0 transceives to/from SDA SCL VAR portB.1 ' PB1 sends clock pulses HMC6352_READ CON $43 ' HMC6352 read address HMC6352_WRITE CON $42 ' HMC6352 write address GET_HEADING CON $41 ' Read in the calculated heading START_CALIB CON $43 ' Start the calibration routine END_CALIB CON $45 ' Finish the calibration routine Heading VAR Word ' Heading read from compass I2C_DATA VAR Byte ' Temporary I2C variable I2C_LSB VAR Bit ' Temporary I2C variable ' -----[ Main Routine ]------------------------------------------------------- DO pause 500 GOSUB Compass_Get_Heading ' Get angle ;DEBUG HOME, "Heading = ", DEC Heading / 10, " degrees" ' Print aingle Lcdout $fe, 1, $fe, $80 ' Clear LCD screen Lcdout $FE, $80, "Heading = ", DEC Heading / 10, " deg" LOOP ' -----[ Subroutines ]-------------------------------------------------------- Compass_Get_Heading: ' Compass module subroutine GOSUB I2C_Start ' Start communications on the I2C buss I2C_DATA = HMC6352_WRITE GOSUB I2C_Write ' Address the HMC6352 in write mode I2C_DATA = GET_HEADING GOSUB I2C_Write ' Send the get heading command GOSUB I2C_Stop ' End communications on the I2C buss GOSUB I2C_Start ' Start communications on the I2C buss I2C_DATA = HMC6352_READ GOSUB I2C_Write ' Address the HMC6352 in read mode PAUSE 6 ' Give the HMC6352 time to calculate the heading GOSUB I2C_Read Heading.HIGHBYTE = I2C_DATA ' Read in the high byte GOSUB I2C_ACK GOSUB I2C_Read Heading.LOWBYTE = I2C_DATA ' Read in the low byte GOSUB I2C_NACK GOSUB I2C_Stop ' End communications on the I2C buss RETURN I2C_Start: LOW SDA ' Pull SDA low LOW SCL ' Pull SCL low RETURN I2C_Stop: LOW SDA ' Pull SDA low INPUT SCL ' Let SCL float high INPUT SDA ' Let SDA float high RETURN I2C_ACK: LOW SDA ' Pull SDA low INPUT SCL ' Let SCL float high LOW SCL ' Pull SCL low INPUT SDA ' Let SDA float high RETURN I2C_NACK: INPUT SDA ' Let SDA float high INPUT SCL ' Let SCL float high LOW SCL ' Pull SCL low RETURN I2C_Read: SHIFTIN SDA, SCL, MSBPRE, [I2C_DATA] ' Read in 8 bits, MSB first RETURN I2C_Write: I2C_LSB = I2C_DATA.BIT0 ' Store the status of the LSB I2C_DATA = I2C_DATA / 2 SHIFTOUT SDA, SCL, MSBFIRST, [I2C_DATA\7] ' Write out the first 7 bits, MSB first IF I2C_LSB THEN INPUT SDA ELSE LOW SDA ' Write the 8th bit endif INPUT SCL ' Using an open collector output LOW SCL INPUT SDA ' Leave SDA as an input INPUT SCL ' Ignore the ACK bit LOW SCL RETURN

At a quick glance you didn't turn off the analog inputs. Get the datasheet.

BobK

I added ADCON1 = 7, still nothing. It's actually irrelevent because I am not even using port A for
anything. There are no interrupts in the code or timers. I can't tell if it's the module or the code that
is the issue. I ported the code from a BS2......it was not THAT drastic of a change over...so I assume
the code should work. Does anyone have test code for this module?

Nick

Do you have pull up resisters on your I2C, clock and data lines? Also I
find it helps not to clear the LCD on each loop and just over write to the location
that is changing. This helps avoid flicker.

Regards

I have a couple 10K pull ups on the lines. Still works erratically, then freezes. I am running my MCU
at 20 MHz, could it operate too quickly porting it to PIC? Maybe the timing is all messed up?

Nick

Fixed it

OK...found the problem. I added a delay in the screen update. Also timing within the I2C was off. I
corrected it. See working code below.

Code:

INCLUDE "Modedefs.Bas" @ Device pic16F877A, HS_OSC, LVP_OFF, WDT_OFF,protect_off DEFINE OSC 20 ; Set port direction and turn off unused peripherals ADCON1 = 7 CMCON = 7 ' shut offcomparators TRISA = %00000000 ' Set PORTA to input "1" or output "0" TRISB = %00000000 ' set portB to output "0" or input "1" TRISC = %00000000 TRISD = %00000000 TRISE = %00000000 ; initialize all ports to low portA = %00000000 portB = %00000000 portC = %00000000 portD = %00000000 portE = %00000000 ; define LCD 4 line x 20, 4 bit interface Define LCD_DREG PORTD Define LCD_DBIT 0 Define LCD_RSREG PORTD Define LCD_RSBIT 4 Define LCD_EREG PORTD Define LCD_EBIT 5 Define LCD_BITS 4 Define LCD_LINES 4 define LCD_COMMANDUS 1500 DEFINE LCD_DATAUS 44 'main2: ' Lcdout $fe, 1, $fe, $80 ' Clear LCD screen ' Lcdout $FE, $80, "testing" ' Pause 2000 ' Wait .5 second ' goto main2 ' -----[ Pins/Constants/Variables ]------------------------------------------- SDA VAR portB.0 ' PB0 transceives to/from SDA SCL VAR portB.1 ' PB1 sends clock pulses HMC6352_READ CON $43 ' HMC6352 read address HMC6352_WRITE CON $42 ' HMC6352 write address GET_HEADING CON $41 ' Read in the calculated heading START_CALIB CON $43 ' Start the calibration routine END_CALIB CON $45 ' Finish the calibration routine Heading VAR Word ' Heading read from compass I2C_DATA VAR byte ' Temporary I2C variable I2C_LSB VAR Bit ' Temporary I2C variable ' -----[ Main Routine ]------------------------------------------------------- DO GOSUB Compass_Get_Heading ' Get angle ;DEBUG HOME, "Heading = ", DEC Heading / 10, " degrees" ' Print aingle Lcdout $fe, 1, $fe, $80 ' Clear LCD screen Lcdout $FE, $80, "Heading = ", DEC Heading / 10, " deg " pause 200 LOOP ' -----[ Subroutines ]-------------------------------------------------------- Compass_Get_Heading: ' Compass module subroutine GOSUB I2C_Start ' Start communications on the I2C buss I2C_DATA = HMC6352_WRITE GOSUB I2C_Write ' Address the HMC6352 in write mode I2C_DATA = GET_HEADING GOSUB I2C_Write ' Send the get heading command GOSUB I2C_Stop ' End communications on the I2C buss GOSUB I2C_Start ' Start communications on the I2C buss I2C_DATA = HMC6352_READ GOSUB I2C_Write ' Address the HMC6352 in read mode PAUSE 6 ' Give the HMC6352 time to calculate the heading GOSUB I2C_Read Heading.HIGHBYTE = I2C_DATA ' Read in the high byte GOSUB I2C_ACK GOSUB I2C_Read Heading.LOWBYTE = I2C_DATA ' Read in the low byte GOSUB I2C_NACK GOSUB I2C_Stop ' End communications on the I2C buss RETURN I2C_Start: LOW SDA ' Pull SDA low LOW SCL ' Pull SCL low pause 1 RETURN I2C_Stop: LOW SDA ' Pull SDA low INPUT SCL ' Let SCL float high INPUT SDA ' Let SDA float high pause 1 RETURN I2C_ACK: LOW SDA ' Pull SDA low INPUT SCL ' Let SCL float high LOW SCL ' Pull SCL low INPUT SDA ' Let SDA float high pause 1 RETURN I2C_NACK: INPUT SDA ' Let SDA float high INPUT SCL ' Let SCL float high LOW SCL ' Pull SCL low pause 1 RETURN I2C_Read: SHIFTIN SDA, SCL, MSBPRE, [I2C_DATA] ' Read in 8 bits, MSB first RETURN I2C_Write: I2C_LSB = I2C_DATA.BIT0 ' Store the status of the LSB I2C_DATA = I2C_DATA / 2 SHIFTOUT SDA, SCL, MSBFIRST, [I2C_DATA\7] ' Write out the first 7 bits, MSB first IF I2C_LSB THEN INPUT SDA ELSE LOW SDA ' Write the 8th bit endif INPUT SCL ' Using an open collector output LOW SCL INPUT SDA ' Leave SDA as an input INPUT SCL ' Ignore the ACK bit LOW SCL RETURN

It's a little late now, as you have yours working nicely. But I was not sure if you saw this or not. It looks to be a bit unfinished. Thought you might be interested anyways:

http://www.picbasic.co.uk/forum/showthread.php?t=8310

I saw that code. I actually have one module that is useless because I tried using that code to
calibrate. I don't know exactly what happened, maybe the timing is off on that routine also, but
the module never worked the same since. I will tweek the calibration code and see if I can restore
the calibration to a useable level.

Nick

Re: problem with HMC6352 compass

Hello,

I have any problem with my code.
I am working with HMC6352 in PROTON but i have any problem with the sensor. I don`t know what happen, Please could you help me?

This is the code

device = 16f876
xtal 20

declare SDA_PIN PORTB.0
DECLARE SCL_PIN PORTB.1

DIM LSB AS WORD
DIM MSB As WORD
Main:
BusouT $42,[$43]
DELAYUS 10
DELAYMS 10000
BUSOUT $42,[$45]
DELAYMS 14
BUSOUT $42,[$4F]
DELAYMS 6
while 1=1
busout $42,[$41]
delayms 10
busin $43,[MSB, LSB]
HRSOUT "VALOR MSB ", DEC mSB, "LSB ", DEC LSB, 13
DELAYMS 500
wend
GOTO mAIN

The problem is that LSB date is incorrect. It is not read. Always show 65535 as value of LSB.