[lm-sensors] Using the I2C kernel layer

[lm-sensors] Using the I2C kernel layer

[Michael Rumpf]

Hi,

I have an external Hygrometer which stores temperature
and humidity snapshots on the device and which can be
read by a Windows software. I would like to write a
Linux program to access the device and read the
values.

After analyzing the Windows software I found out that
they are using a really "simple" I2C interface to the
device, the plain serial port. Especially the status
lines DTR (SCL), CTS (SDA Write), DSR (SDA Read). The
chip that stores the values is an eeprom Atmel
AT24C128/256 (?).

After digging through the I2C/lm_sensors code/docs I
found that much of the infrastructure for accessing
eeproms has already been implemented in a modular way.

Unfortunately I had to read about some restrictions,
like that eeproms with more than 256Bytes (?) capacity
are not supported and that there is not write support
for eeproms. The device probably needs write support
to reset the values in the ring-buffer.

Because I'm new to I2C and kernel driver development I
ask myself about the best approach to access the
device, described above. There are currently too many
unknown variables in my approach, so it would be kind
if someone with good knowledge of the kernel I2C
infrastructure could shortly explain what the best
approach would be to write a driver for the device.
Would it be possible to write a simple bus-driver,
like the parport(-light) driver and use an extended
version of the eeprom client driver to access the
device?

I would prefer this approach as it would allow me to
use all the user-space I2C tools that access the
I2C/lm_sensors APIs. But if the effort for extending
the eeprom driver is high I need to investigate other
possibilities as I would like to get something working
really fast.

Thanks in advance,
   Michael


Michael Rumpf # Meissener Str. 4 # 71065 Sindelfingen # Germany
Tel/Fax +49 7031 415883/884
WWW http://fsinfo.cs.uni-sb.de/~miru
              Misraet Dir voll Dein Tagesplan,
              sei Abends Dir als Trost bekraeftigt,
              Du hast zwar heute nichts getan,
              doch warst den ganzen Tag beschaeftigt.

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com 

[lm-sensors] Using the I2C kernel layer

[Mark Studebaker]

the userspace eeprom writing tools in prog/eepromer may help you.
also see the documents in http://www2.lm-sensors.nu/~lm78/docs.html

Michael Rumpf wrote:
> Hi,
> 
> I have an external Hygrometer which stores temperature
> and humidity snapshots on the device and which can be
> read by a Windows software. I would like to write a
> Linux program to access the device and read the
> values.
> 
> After analyzing the Windows software I found out that
> they are using a really "simple" I2C interface to the
> device, the plain serial port. Especially the status
> lines DTR (SCL), CTS (SDA Write), DSR (SDA Read). The
> chip that stores the values is an eeprom Atmel
> AT24C128/256 (?).
> 
> After digging through the I2C/lm_sensors code/docs I
> found that much of the infrastructure for accessing
> eeproms has already been implemented in a modular way.
> 
> Unfortunately I had to read about some restrictions,
> like that eeproms with more than 256Bytes (?) capacity
> are not supported and that there is not write support
> for eeproms. The device probably needs write support
> to reset the values in the ring-buffer.
> 
> Because I'm new to I2C and kernel driver development I
> ask myself about the best approach to access the
> device, described above. There are currently too many
> unknown variables in my approach, so it would be kind
> if someone with good knowledge of the kernel I2C
> infrastructure could shortly explain what the best
> approach would be to write a driver for the device.
> Would it be possible to write a simple bus-driver,
> like the parport(-light) driver and use an extended
> version of the eeprom client driver to access the
> device?
> 
> I would prefer this approach as it would allow me to
> use all the user-space I2C tools that access the
> I2C/lm_sensors APIs. But if the effort for extending
> the eeprom driver is high I need to investigate other
> possibilities as I would like to get something working
> really fast.
> 
> Thanks in advance,
>    Michael
> 
> 
> Michael Rumpf # Meissener Str. 4 # 71065 Sindelfingen # Germany
> Tel/Fax +49 7031 415883/884
> WWW http://fsinfo.cs.uni-sb.de/~miru
>               Misraet Dir voll Dein Tagesplan,
>               sei Abends Dir als Trost bekraeftigt,
>               Du hast zwar heute nichts getan,
>               doch warst den ganzen Tag beschaeftigt.
> 
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around 
> http://mail.yahoo.com 
> 
> _______________________________________________
> lm-sensors mailing list
> lm-sensors@lm-sensors.org
> http://lists.lm-sensors.org/mailman/listinfo/lm-sensors