Documentation/hwmon/lm70


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47

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
  * National Semiconductor LM71
    Datasheet: http://www.ti.com/product/LM71
  * National Semiconductor LM74
    Datasheet: http://www.ti.com/product/LM74

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 LM74 and TMP121/TMP123 are very similar; main difference is 13-bit
temperature data (0.0625 degrees celsius resolution).

The LM71 is also very similar; main difference is 14-bit temperature
data (0.03125 degrees celsius resolution).

Thanks to
---------
Jean Delvare <jdelvare@suse.de> for mentoring the hwmon-side driver
development.