| Kernel driver w1_ds2438 |
| ======================= |
| |
| Supported chips: |
| * Maxim DS2438 Smart Battery Monitor |
| |
| supported family codes: |
| W1_FAMILY_DS2438 0x26 |
| |
| Author: Mariusz Bialonczyk <manio@skyboo.net> |
| |
| Description |
| ----------- |
| |
| The DS2438 chip provides several functions that are desirable to carry in |
| a battery pack. It also has a 40 bytes of nonvolatile EEPROM. |
| Because the ability of temperature, current and voltage measurement, the chip |
| is also often used in weather stations and applications such as: rain gauge, |
| wind speed/direction measuring, humidity sensing, etc. |
| |
| Current support is provided through the following sysfs files (all files |
| except "iad" are readonly): |
| |
| "iad" |
| ----- |
| This file controls the 'Current A/D Control Bit' (IAD) in the |
| Status/Configuration Register. |
| Writing a zero value will clear the IAD bit and disables the current |
| measurements. |
| Writing value "1" is setting the IAD bit (enables the measurements). |
| The IAD bit is enabled by default in the DS2438. |
| |
| When writing to sysfs file bits 2-7 are ignored, so it's safe to write ASCII. |
| An I/O error is returned when there is a problem setting the new value. |
| |
| "page0" |
| ------- |
| This file provides full 8 bytes of the chip Page 0 (00h). |
| This page contains the most frequently accessed information of the DS2438. |
| Internally when this file is read, the additional CRC byte is also obtained |
| from the slave device. If it is correct, the 8 bytes page data are passed |
| to userspace, otherwise an I/O error is returned. |
| |
| "temperature" |
| ------------- |
| Opening and reading this file initiates the CONVERT_T (temperature conversion) |
| command of the chip, afterwards the temperature is read from the device |
| registers and provided as an ASCII decimal value. |
| |
| Important: The returned value has to be divided by 256 to get a real |
| temperature in degrees Celsius. |
| |
| "vad", "vdd" |
| ------------ |
| Opening and reading this file initiates the CONVERT_V (voltage conversion) |
| command of the chip. |
| |
| Depending on a sysfs filename a different input for the A/D will be selected: |
| vad: general purpose A/D input (VAD) |
| vdd: battery input (VDD) |
| |
| After the voltage conversion the value is returned as decimal ASCII. |
| Note: To get a volts the value has to be divided by 100. |
