Kernel driver lm70¶
National Semiconductor LM70
Texas Instruments TMP121/TMP123
Texas Instruments TMP122/TMP124
National Semiconductor LM71
National Semiconductor LM74
Kaiwan N Billimoria <firstname.lastname@example.org>
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/TMP122/TMP123/TMP124 are very similar; main difference is 13-bit temperature data (0.0625 degrees celsius resolution).
The TMP122/TMP124 also feature configurable temperature thresholds.
The LM71 is also very similar; main difference is 14-bit temperature data (0.03125 degrees celsius resolution).