Derp!  That did the trick.  (See test output below.  It prints the expected 
default values from my sensor.)

Thanks again.  :-)

debian@beaglebone:~$ uname -a
Linux beaglebone 4.4.54-ti-r93 #1 SMP Fri Mar 17 13:08:22 UTC 2017 armv7l 
GNU/Linux
debian@beaglebone:~$ gcc compass.c
debian@beaglebone:~$ ./a.out
Starting HMC6352 Compass Test.
EEPROM reg[0x00] = 0x42
EEPROM reg[0x01] = 0x00
EEPROM reg[0x02] = 0x00
EEPROM reg[0x03] = 0x00
EEPROM reg[0x04] = 0x00
EEPROM reg[0x05] = 0x01
EEPROM reg[0x06] = 0x04
EEPROM reg[0x07] = 0x06
EEPROM reg[0x08] = 0x50


On Sunday, June 18, 2017 at 11:53:30 AM UTC-5, RobertCNelson wrote:
>
> On Sun, Jun 18, 2017 at 10:59 AM, mark whitney <[email protected] 
> <javascript:>> wrote: 
> > Thank you for the reply. 
> > 
> > As a sanity check, I went back to Debian 7.5.  And it just worked 
> without 
> > having to do any extra configuration.  See below for a dump of results. 
>  My 
> > compass device appears at its default address 0x21.  I sent a command 
> (0x72) 
> > to read EEPROM register 0x00 and read back the expected byte (0x42). 
> > 
> > With the Debian 8.7 image, I got error messages when I tried the i2cget 
> and 
> > i2cset commands.  I also noticed that the i2cdetect -y -r 1 command runs 
> > very slowly compared to the Debian 7.5 image, it takes a second or so to 
> > print each address entry. 
> > 
> > Is there some extra configuration I need to do in Debian 8.7?  Like edit 
> the 
> > uEnv.txt file?  Load an overlay?  Or tweak a DTS file? 
> > 
> > Thanks! 
> > 
> > 
> > debian@beaglebone:~$ uname -a 
> > Linux beaglebone 3.8.13-bone50 #1 SMP Tue May 13 13:24:52 UTC 2014 
> armv7l 
> > GNU/Linux 
> > debian@beaglebone:~$ i2cdetect -y -r 1 
> >      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f 
> > 00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
> > 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
> > 20: -- 21 -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
> > 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
> > 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
> > 50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- -- 
> > 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
> > 70: -- -- -- -- -- -- -- -- 
> > debian@beaglebone:~$ i2cset -y 1 0x21 0x72 0x00 
> > debian@beaglebone:~$ i2cget -y 1 0x21 
> > 0x42 
>
> Wrong bus.. 
>
> With 3.8.13 the i2c bus #'s where setup on a first come basis.. 
>
> With newer kernel's the bus #'s actually corresponds to the i2c bus 
> #..  In this case: &i2c2.. 
>
> So use: 
>
> i2cdetect -y -r 2 
>
> Regards, 
>
> -- 
> Robert Nelson 
> https://rcn-ee.com/ 
>

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