Documentation/hwmon/max31827.rst - linux - Git at Google

 .. SPDX-License-Identifier: GPL-2.0

 Kernel driver max31827
 ======================

 Supported chips:

   * Maxim MAX31827

     Prefix: 'max31827'

     Addresses scanned: I2C 0x40 - 0x5f

     Datasheet: Publicly available at the Analog Devices website

   * Maxim MAX31828

     Prefix: 'max31828'

     Addresses scanned: I2C 0x40 - 0x5f

     Datasheet: Publicly available at the Analog Devices website

   * Maxim MAX31829

     Prefix: 'max31829'

     Addresses scanned: I2C 0x40 - 0x5f

     Datasheet: Publicly available at the Analog Devices website


 Authors:
 	- Daniel Matyas <daniel.matyas@analog.com>

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

 The chips supported by this driver are quite similar. The only difference
 between them is found in the default power-on behaviour of the chips. While the
 MAX31827's fault queue is set to 1, the other two chip's fault queue is set to
 4. Besides this, the MAX31829's alarm active state is high, while the other two
 chip's alarms are active on low. It is important to note that the chips can be
 configured to operate in the same manner with 1 write operation to the
 configuration register. From here on, we will refer to all these chips as
 MAX31827.

 MAX31827 implements a temperature sensor with a 6 WLP packaging scheme. This
 sensor measures the temperature of the chip itself.

 MAX31827 has low and over temperature alarms with an effective value and a
 hysteresis value: -40 and -30 degrees for under temperature alarm and +100 and
 +90 degrees for over temperature alarm.

 The alarm can be configured in comparator and interrupt mode from the
 devicetree. In Comparator mode, the OT/UT status bits have a value of 1 when the
 temperature rises above the TH value or falls below TL, which is also subject to
 the Fault Queue selection. OT status returns to 0 when the temperature drops
 below the TH_HYST value or when shutdown mode is entered. Similarly, UT status
 returns to 0 when the temperature rises above TL_HYST value or when shutdown
 mode is entered.

 In interrupt mode exceeding TH also sets OT status to 1, which remains set until
 a read operation is performed on the configuration/status register (max or min
 attribute); at this point, it returns to 0. Once OT status is set to 1 from
 exceeding TH and reset, it is set to 1 again only when the temperature drops
 below TH_HYST. The output remains asserted until it is reset by a read. It is
 set again if the temperature rises above TH, and so on. The same logic applies
 to the operation of the UT status bit.

 Putting the MAX31827 into shutdown mode also resets the OT/UT status bits. Note
 that if the mode is changed while OT/UT status bits are set, an OT/UT status
 reset may be required before it begins to behave normally. To prevent this,
 it is recommended to perform a read of the configuration/status register to
 clear the status bits before changing the operating mode.

 The conversions can be manual with the one-shot functionality and automatic with
 a set frequency. When powered on, the chip measures temperatures with 1 conv/s.
 The conversion rate can be modified with update_interval attribute of the chip.
 Conversion/second = 1/update_interval. Thus, the available options according to
 the data sheet are:

 - 64000 (ms) = 1 conv/64 sec
 - 32000 (ms) = 1 conv/32 sec
 - 16000 (ms) = 1 conv/16 sec
 - 4000 (ms) = 1 conv/4 sec
 - 1000 (ms) = 1 conv/sec (default)
 - 250 (ms) = 4 conv/sec
 - 125 (ms) = 8 conv/sec

 Enabling the device when it is already enabled has the side effect of setting
 the conversion frequency to 1 conv/s. The conversion time varies depending on
 the resolution.

 The conversion time doubles with every bit of increased resolution. The
 available resolutions are:

 - 8 bit -> 8.75 ms conversion time
 - 9 bit -> 17.5 ms conversion time
 - 10 bit -> 35 ms conversion time
 - 12 bit (default) -> 140 ms conversion time

 There is a temp1_resolution attribute which indicates the unit change in the
 input temperature in milli-degrees C.

 - 1000 mC -> 8 bit
 - 500 mC -> 9 bit
 - 250 mC -> 10 bit
 - 62 mC -> 12 bit (default) - actually this is 62.5, but the fil returns 62

 When chip is in shutdown mode and a read operation is requested, one-shot is
 triggered, the device waits for <conversion time> ms, and only after that is
 the temperature value register read. Note that the conversion times are rounded
 up to the nearest possible integer.

 The LSB of the temperature values is 0.0625 degrees Celsius, but the values of
 the temperatures are displayed in milli-degrees. This means, that some data is
 lost. The step between 2 consecutive values is 62 or 63. This effect can be seen
 in the writing of alarm values too. For positive numbers the user-input value
 will always be rounded down to the nearest possible value, for negative numbers
 the user-input will always be rounded up to the nearest possible value.

 Bus timeout resets the I2C-compatible interface when SCL is low for more than
 30ms (nominal).

 Alarm polarity determines if the active state of the alarm is low or high. The
 behavior for both settings is dependent on the Fault Queue setting. The ALARM
 pin is an open-drain output and requires a pullup resistor to operate.

 The Fault Queue bits select how many consecutive temperature faults must occur
 before overtemperature or undertemperature faults are indicated in the
 corresponding status bits.

 Notes
 -----

 PEC is not implemented.
	.. SPDX-License-Identifier: GPL-2.0

	Kernel driver max31827
	======================

	Supported chips:

	* Maxim MAX31827

	Prefix: 'max31827'

	Addresses scanned: I2C 0x40 - 0x5f

	Datasheet: Publicly available at the Analog Devices website

	* Maxim MAX31828

	Prefix: 'max31828'

	Addresses scanned: I2C 0x40 - 0x5f

	Datasheet: Publicly available at the Analog Devices website

	* Maxim MAX31829

	Prefix: 'max31829'

	Addresses scanned: I2C 0x40 - 0x5f

	Datasheet: Publicly available at the Analog Devices website


	Authors:
	- Daniel Matyas <daniel.matyas@analog.com>

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

	The chips supported by this driver are quite similar. The only difference
	between them is found in the default power-on behaviour of the chips. While the
	MAX31827's fault queue is set to 1, the other two chip's fault queue is set to
	4. Besides this, the MAX31829's alarm active state is high, while the other two
	chip's alarms are active on low. It is important to note that the chips can be
	configured to operate in the same manner with 1 write operation to the
	configuration register. From here on, we will refer to all these chips as
	MAX31827.

	MAX31827 implements a temperature sensor with a 6 WLP packaging scheme. This
	sensor measures the temperature of the chip itself.

	MAX31827 has low and over temperature alarms with an effective value and a
	hysteresis value: -40 and -30 degrees for under temperature alarm and +100 and
	+90 degrees for over temperature alarm.

	The alarm can be configured in comparator and interrupt mode from the
	devicetree. In Comparator mode, the OT/UT status bits have a value of 1 when the
	temperature rises above the TH value or falls below TL, which is also subject to
	the Fault Queue selection. OT status returns to 0 when the temperature drops
	below the TH_HYST value or when shutdown mode is entered. Similarly, UT status
	returns to 0 when the temperature rises above TL_HYST value or when shutdown
	mode is entered.

	In interrupt mode exceeding TH also sets OT status to 1, which remains set until
	a read operation is performed on the configuration/status register (max or min
	attribute); at this point, it returns to 0. Once OT status is set to 1 from
	exceeding TH and reset, it is set to 1 again only when the temperature drops
	below TH_HYST. The output remains asserted until it is reset by a read. It is
	set again if the temperature rises above TH, and so on. The same logic applies
	to the operation of the UT status bit.

	Putting the MAX31827 into shutdown mode also resets the OT/UT status bits. Note
	that if the mode is changed while OT/UT status bits are set, an OT/UT status
	reset may be required before it begins to behave normally. To prevent this,
	it is recommended to perform a read of the configuration/status register to
	clear the status bits before changing the operating mode.

	The conversions can be manual with the one-shot functionality and automatic with
	a set frequency. When powered on, the chip measures temperatures with 1 conv/s.
	The conversion rate can be modified with update_interval attribute of the chip.
	Conversion/second = 1/update_interval. Thus, the available options according to
	the data sheet are:

	- 64000 (ms) = 1 conv/64 sec
	- 32000 (ms) = 1 conv/32 sec
	- 16000 (ms) = 1 conv/16 sec
	- 4000 (ms) = 1 conv/4 sec
	- 1000 (ms) = 1 conv/sec (default)
	- 250 (ms) = 4 conv/sec
	- 125 (ms) = 8 conv/sec

	Enabling the device when it is already enabled has the side effect of setting
	the conversion frequency to 1 conv/s. The conversion time varies depending on
	the resolution.

	The conversion time doubles with every bit of increased resolution. The
	available resolutions are:

	- 8 bit -> 8.75 ms conversion time
	- 9 bit -> 17.5 ms conversion time
	- 10 bit -> 35 ms conversion time
	- 12 bit (default) -> 140 ms conversion time

	There is a temp1_resolution attribute which indicates the unit change in the
	input temperature in milli-degrees C.

	- 1000 mC -> 8 bit
	- 500 mC -> 9 bit
	- 250 mC -> 10 bit
	- 62 mC -> 12 bit (default) - actually this is 62.5, but the fil returns 62

	When chip is in shutdown mode and a read operation is requested, one-shot is
	triggered, the device waits for <conversion time> ms, and only after that is
	the temperature value register read. Note that the conversion times are rounded
	up to the nearest possible integer.

	The LSB of the temperature values is 0.0625 degrees Celsius, but the values of
	the temperatures are displayed in milli-degrees. This means, that some data is
	lost. The step between 2 consecutive values is 62 or 63. This effect can be seen
	in the writing of alarm values too. For positive numbers the user-input value
	will always be rounded down to the nearest possible value, for negative numbers
	the user-input will always be rounded up to the nearest possible value.

	Bus timeout resets the I2C-compatible interface when SCL is low for more than
	30ms (nominal).

	Alarm polarity determines if the active state of the alarm is low or high. The
	behavior for both settings is dependent on the Fault Queue setting. The ALARM
	pin is an open-drain output and requires a pullup resistor to operate.

	The Fault Queue bits select how many consecutive temperature faults must occur
	before overtemperature or undertemperature faults are indicated in the
	corresponding status bits.

	Notes
	-----

	PEC is not implemented.