[lm-sensors] TI TMP421 chip address

Jean Delvare khali at linux-fr.org
Wed May 27 13:59:01 CEST 2009


On Wed, 27 May 2009 13:08:19 +0200, Hans de Goede wrote:
> 
> 
> On 05/27/2009 11:15 AM, Andre Prendel wrote:
> > Hi Hans,
> >
> > looking in the datasheet of the TMP421 sensor chip
> >
> > http://focus.ti.com/docs/prod/folders/print/tmp421.html,
> >
> > I saw the following addresses.
> >
> > TMP421  100 11xx
> > TMP422  100 11xx
> > TMP423A 100 1100
> > TMP423B 100 1101
> >
> > But the preliminary driver of your students uses 0x2a.
> >
> >   /* Addresses to scan */
> >   static unsigned short normal_i2c[] = { 0x2a, I2C_CLIENT_END };
> >
> > 0x2a == 010 1010b, right?
> >
> 
> Right.
> 
> > Do I misunderstand something?
> 
> No, what my students did in there was wrong, they only put the
> address in there to which the sample I gave them is wired
> 
> The addresses to scan should be:
> static unsigned short normal_i2c[] = { 0x1c, 0x1d, 0x1e, 0x1f,
>    0x2a, 0x4c, 0x4d, 0x4e, 0x4f, I2C_CLIENT_END };
> 
> But we better run those past Jean, to see if any of
> those are dangerous to scan by default, Jean ?

0x2a and 0x4c-0x4f are very popular addresses for hardware monitoring
chips and can be scanned. 0x1c-0x1f is something new, sensors-detect
doesn't even scan 0x1c-0x1e at the moment, only 0x1f is scanned (for
the Maxim MAX6650/MAX6651.)

Where do the 0x1c-0x1f and 0x2a addresses come from? The possible
addresses listed above by Andre were only 0x4c-0x4f.

On which systems are these chips found? If only on embedded systems and
not on PC, the safe option would be to only scan 0x2a and 0x4c-0x4f. On
embedded systems, probing won't be used anyway, so devices can be
instantiated at any address, regardless of what the driver lists.

Please add detection of these chips to sensors-detect, for addresses
0x2a and 0x4c-0x4f, and add them to the wiki.

-- 
Jean Delvare




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