RoboSavvy Forum

I2C Compass

2009-10-20T12:25:06+01:00

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

Statistics: Posted by limor — Tue Oct 20, 2009 12:25 pm

I2C Compass

2009-09-07T00:49:03+01:00

phpBB [media]

Statistics: Posted by Gort — Mon Sep 07, 2009 12:49 am

I2C Compass

2009-09-06T20:52:02+01:00

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

Statistics: Posted by Gort — Sun Sep 06, 2009 8:52 pm

I2C Compass

2009-08-30T10:01:47+01:00

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

Statistics: Posted by i-Bot — Sun Aug 30, 2009 10:01 am

I2C Compass

2009-08-30T02:31:31+01:00

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

Statistics: Posted by Gort — Sun Aug 30, 2009 2:31 am

I2C Compass

2009-08-29T13:55:46+01:00

&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.

Statistics: Posted by i-Bot — Sat Aug 29, 2009 1:55 pm

I2C Compass

2009-08-29T02:41:54+01:00

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:.

Statistics: Posted by Gort — Sat Aug 29, 2009 2:41 am

I2C Compass

2009-08-25T13:07:32+01:00

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."

Statistics: Posted by NovaOne — Tue Aug 25, 2009 1:07 pm

I2C Compass

2009-08-23T22:29:29+01:00

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.

Statistics: Posted by Gort — Sun Aug 23, 2009 10:29 pm

I2C Compass

2009-08-23T14:56:11+01:00

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

Statistics: Posted by RoboJeronimo — Sun Aug 23, 2009 2:56 pm

I2C Compass

2009-08-23T04:09:48+01:00

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.

Statistics: Posted by Gort — Sun Aug 23, 2009 4:09 am

I2C Compass

2009-08-15T21:10:57+01:00

Still trying to find time to hook up my compass. I am curious to see the compass reading when displayed on the LCD.

Statistics: Posted by Gort — Sat Aug 15, 2009 9:10 pm

I2C Compass

2009-08-15T19:54:09+01:00

I would of expected that the distribution was largely equal but yes with out calibration you would not be able to know for sure that 127 was 180 degrees etc.
Isn't this the whole point of calibration. These values should be derived from the calibration lookup table not the values direct from the sensor .

John

Statistics: Posted by ProblemChild — Sat Aug 15, 2009 7:54 pm

I2C Compass

2009-08-15T17:44:52+01:00

Hi, I found the problem of my code for turning 180º

The error is I assumed the compass gives 127 (127=255/2) with a 180º angle, but the compass doesn't distribute de values proportinally around the full circle.

So the sentence IF BRUJULA<127 THEN GOSUB LEFT_TURN is wrong

Statistics: Posted by RoboJeronimo — Sat Aug 15, 2009 5:44 pm

I2C Compass

2009-08-14T09:01:21+01:00

I'm under the impression supported by (1) that you only need one set of resistors for the entire bus. I ass -u-me it's on the Arduino .

(1) http://www.robot-electronics.co.uk/htm/ ... 2c_bus.htm

Statistics: Posted by ProblemChild — Fri Aug 14, 2009 9:01 am