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drivers: hwmon: max31827: add max31875
Add support for MAX31875 Low-Power I2C Temperature Sensor in MAX31827 driver Signed-off-by: John Erasmus Mari Geronimo <[email protected]>
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@@ -29,9 +29,18 @@ Supported chips: | |
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| Datasheet: Publicly available at the Analog Devices website | ||
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| * Maxim MAX31875 | ||
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| Prefix: 'max31875' | ||
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| Addresses scanned: I2C 0x48 - 0x4f | ||
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| Datasheet: Publicly available at the Analog Devices website | ||
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| Authors: | ||
| - Daniel Matyas <[email protected]> | ||
| - John Erasmus Mari Geronimo <[email protected]> | ||
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| Description | ||
| ----------- | ||
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@@ -45,13 +54,20 @@ 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. | ||
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| MAX31827 implements a temperature sensor with a 6 WLP packaging scheme. This | ||
| sensor measures the temperature of the chip itself. | ||
| This driver also supports the MAX31875. Its fault queue is set to 1 and it has | ||
| no alarm polarity. | ||
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| MAX31827 implements a temperature sensor with a 6 WLP packaging scheme while | ||
| MAX31875 has a 4 WLP packaging scheme. This sensor measures the temperature of | ||
| the chip itself. | ||
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| 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. | ||
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| MAX31875 has only an over temperature alarm with an effective value and a | ||
| hysteresis value: +80 and +75 degrees. | ||
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| 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 | ||
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@@ -75,19 +91,22 @@ it is recommended to perform a read of the configuration/status register to | |
| clear the status bits before changing the operating mode. | ||
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| 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. | ||
| a set frequency. When powered on, the MAX31827 measures temperatures with 1 | ||
| conv/s while the MAX31875 measures temperatures with 0.25 conv/s or 1 conv/4s. | ||
| 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: | ||
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| - 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) | ||
| - 4000 (ms) = 1 conv/4 sec (MAX31875 default) | ||
| - 1000 (ms) = 1 conv/sec (MAX31827 default) | ||
| - 250 (ms) = 4 conv/sec | ||
| - 125 (ms) = 8 conv/sec | ||
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| The MAX31875 only supports the last four values above. | ||
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| 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. | ||
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@@ -97,16 +116,16 @@ available resolutions are: | |
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| - 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 | ||
| - 10 bit (MAX31875 default) -> 35 ms conversion time | ||
| - 12 bit (MAX31827 default) -> 140 ms conversion time | ||
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| There is a temp1_resolution attribute which indicates the unit change in the | ||
| input temperature in milli-degrees C. | ||
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| - 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 | ||
| - 250 mC -> 10 bit (MAX31875 default) | ||
| - 62 mC -> 12 bit (MAX31827 default) - actually this is 62.5, but the fil returns 62 | ||
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| 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 | ||
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@@ -125,7 +144,8 @@ Bus timeout resets the I2C-compatible interface when SCL is low for more than | |
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| 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. | ||
| pin is an open-drain output and requires a pullup resistor to operate. The | ||
| MAX31875 does not have this feature. | ||
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| The Fault Queue bits select how many consecutive temperature faults must occur | ||
| before overtemperature or undertemperature faults are indicated in the | ||
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