xref: /openbmc/linux/Documentation/hwmon/lm70.rst (revision 0a94608f)
1Kernel driver lm70
2==================
3
4Supported chips:
5
6  * National Semiconductor LM70
7
8    Datasheet: http://www.national.com/pf/LM/LM70.html
9
10  * Texas Instruments TMP121/TMP123
11
12    Information: http://focus.ti.com/docs/prod/folders/print/tmp121.html
13
14  * Texas Instruments TMP122/TMP124
15
16    Information: https://www.ti.com/product/tmp122
17
18  * Texas Instruments TMP125
19
20    Information: https://www.ti.com/product/tmp125
21
22  * National Semiconductor LM71
23
24    Datasheet: https://www.ti.com/product/LM71
25
26  * National Semiconductor LM74
27
28    Datasheet: https://www.ti.com/product/LM74
29
30
31Author:
32	Kaiwan N Billimoria <kaiwan@designergraphix.com>
33
34Description
35-----------
36
37This driver implements support for the National Semiconductor LM70
38temperature sensor.
39
40The LM70 temperature sensor chip supports a single temperature sensor.
41It communicates with a host processor (or microcontroller) via an
42SPI/Microwire Bus interface.
43
44Communication with the LM70 is simple: when the temperature is to be sensed,
45the driver accesses the LM70 using SPI communication: 16 SCLK cycles
46comprise the MOSI/MISO loop. At the end of the transfer, the 11-bit 2's
47complement digital temperature (sent via the SIO line), is available in the
48driver for interpretation. This driver makes use of the kernel's in-core
49SPI support.
50
51As a real (in-tree) example of this "SPI protocol driver" interfacing
52with a "SPI master controller driver", see drivers/spi/spi_lm70llp.c
53and its associated documentation.
54
55The LM74 and TMP121/TMP122/TMP123/TMP124 are very similar; main difference is
5613-bit temperature data (0.0625 degrees celsius resolution).
57
58The TMP122/TMP124 also feature configurable temperature thresholds.
59
60The TMP125 is less accurate and provides 10-bit temperature data
61with 0.25 degrees Celsius resolution.
62
63The LM71 is also very similar; main difference is 14-bit temperature
64data (0.03125 degrees celsius resolution).
65
66Thanks to
67---------
68Jean Delvare <jdelvare@suse.de> for mentoring the hwmon-side driver
69development.
70