path: root/Documentation/hwmon/lm70

Kernel driver lm70
==================

Supported chips:
  * National Semiconductor LM70
    Datasheet: http://www.national.com/pf/LM/LM70.html
  * Texas Instruments TMP121/TMP123
    Information: http://focus.ti.com/docs/prod/folders/print/tmp121.html

Author:
        Kaiwan N Billimoria <kaiwan@designergraphix.com>

Description
-----------

This driver implements support for the National Semiconductor LM70
temperature sensor.

The LM70 temperature sensor chip supports a single temperature sensor.
It communicates with a host processor (or microcontroller) via an
SPI/Microwire Bus interface.

Communication with the LM70 is simple: when the temperature is to be sensed,
the driver accesses the LM70 using SPI communication: 16 SCLK cycles
comprise the MOSI/MISO loop. At the end of the transfer, the 11-bit 2's
complement digital temperature (sent via the SIO line), is available in the
driver for interpretation. This driver makes use of the kernel's in-core
SPI support.

As a real (in-tree) example of this "SPI protocol driver" interfacing
with a "SPI master controller driver", see drivers/spi/spi_lm70llp.c
and its associated documentation.

The TMP121/TMP123 are very similar; main differences are 4 wire SPI inter-
face (read only) and 13-bit temperature data (0.0625 degrees celsius reso-
lution).

Thanks to
---------
Jean Delvare <khali@linux-fr.org> for mentoring the hwmon-side driver
development.