I2C Compass

[Gort]

I have had no luck so far getting my compass to work using NovaOne's code. I am using the PWM ports 0 and 1. The compass value being displayed on my LCD is always 255? Not sure what I am doing wrong.

[RoboJeronimo]

At the beggining I had the same problem. That's wrong port conection. Are your constants...

CONST SDA = 0 'Use port 0 for Data, constant SDA
CONST SCL = 1 'Use port 1 for Clock, constant SCL

or

CONST SDA = 1 'Use port 0 for Data, constant SDA
CONST SCL = 0 'Use port 1 for Clock, constant SCL

[Gort]

My constants are

CONST SDA = 46 'Use port 46 for Data, constant SDA
CONST SCL = 47 'Use port 47 for Clock, constant SCL

I should have said that I am using the PWM connections 0 and 1 which are ports 46 and 47.

[NovaOne]

I'd like to help Gort...but its all in this thread...my cards are on the table....

as Dr. Lanning said..."I'm sorry. My responses are limited. You must ask the right questions."

[Gort]

My issue is the compass address. NovaOne is using the CMPS03 which has an address of 0x60. I am using the HMC6352 which has a compass address of 0x42. I also have two more questions about NovaOne's code. He sets the I2cAddr in Main: too &Hc0 which I think is a pointer variable, like in C. Can I use a hex number instead for my compass address which is 0x42 or do I need to use a pointer variable? The other question is I am not sure what I2cReg = 1 is doing in Main:.

[i-Bot]

&H is just the prefix to say the number is in HEX to the Robobasic compiler so &HC0 is 0x0c and &H42 would be 0x42 in C speak.

I2cReg = 1 specifies the register to be read from the compass in the I2cByteRead subroutine. The CMPS03 appears as a bank of memory over the I2C bus.

Your HMC6352 is different using a seperate command and response. This means the I2CByteRead routine will not work for you.

You need a couple of new subroutines:
DIM I2cData as INTEGER

WriteA:
GOSUB I2cStart
I2cBuf = I2cAddr
GOSUB I2cOutByte
I2cBuf = "A"
GOSUB I2cOutByte
RETURN

ReadBearing:
GOSUB I2cStart
I2cBuf = I2cAddr OR 1 ' or in the read bit to address
GOSUB I2cOutByte
GOSUB I2cInByte
I2cDataWord = I2cBuf * 256
GOSUB I2cInByte
I2cDataWord = I2cDataWord + I2CInByte
GOSUB I2cStop
RETURN

Then from Main call these with the required delay between.

I didn't check these and my head is in C mode today, so you need to work on them.

[Gort]

Thanks I-Bot, here is my code so far. Now the issue is that I am alwas getting a value of 10 for the compass.

Main:
I2cAddr = &H42 'Default address of compass
I2cReg = 1 'Register containing Compass bearing as a single Byte
GOSUB WriteA
DELAY 100
GOSUB ReadBearing
PRINT &HFE,&H01
PRINT "heading = "
PRINT FORMAT (I2cDataWord, DEC)
DELAY 4000
GOTO Main

WriteA:
GOSUB I2cStart
I2cBuf = I2cAddr
GOSUB I2cOutByte
I2cBuf = "A"
GOSUB I2cOutByte
PRINT &HFE,&H01
PRINT "Done with WriteA"
DELAY 1000
RETURN

ReadBearing:
GOSUB I2cStart
I2cBuf = I2cAddr OR 1 ' or in the read bit to address
GOSUB I2cOutByte
GOSUB I2cInByte
I2cDataWord = I2cBuf * 256
GOSUB I2cInByte
I2cDataWord = I2cDataWord + I2cData
GOSUB I2cStop
PRINT &HFE,&H01
PRINT "Done with ReadBearing"
PRINT FORMAT (I2cData, DEC)
DELAY 1000
RETURN

[i-Bot]

Try this:
Main:
I2cAddr = &H42 'Default address of compass
'I2cReg = 1 '!!Not needed for HMC
GOSUB WriteA
DELAY 100
GOSUB ReadBearing
PRINT &HFE,&H01
PRINT "heading = "
PRINT FORMAT (I2cDataWord, DEC)
DELAY 4000
GOTO Main

WriteA:
GOSUB I2cStart
I2cBuf = I2cAddr
GOSUB I2cOutByte
I2cBuf = "A"
GOSUB I2cOutByte
GOSUB I2cStop ' !! I missed the stop
PRINT &HFE,&H01
PRINT "Done with WriteA"
DELAY 1000
RETURN

ReadBearing:
GOSUB I2cStart
I2cBuf = I2cAddr OR 1 ' or in the read bit to address
GOSUB I2cOutByte
I2cAckBit = 0 'NAck !!Proper handling of response
GOSUB I2cInByte
I2cDataWord = I2cBuf * 256
I2cAckBit = 1 'Ack last byte
GOSUB I2cInByte
I2cDataWord = I2cDataWord + I2cData
GOSUB I2cStop
PRINT &HFE,&H01
PRINT "Done with ReadBearing"
PRINT FORMAT (I2cData, DEC)
DELAY 1000
RETURN

[Gort]

The code in the below PDF is not perfect but it works with the SparkFun I2C HMC6352 compass. Thanks I-Bot and NovaOne for your help.

http://robosavvy.com/Builders/Gort/Spar ... on%201.pdf

[Gort]

phpBB [media]

[limor]

I updated the Robonova Knowledgebase and added this Sparkfun module solution link. btw: The module is available at RoboSavvy.com/store