diff options
| author | Luiz Sampaio <sampaio.ime@gmail.com> | 2021-05-19 19:30:46 -0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-05-21 14:51:33 +0200 |
| commit | c999fbbdcf778c2ea77f59e26d7448a1ab8fa8a2 (patch) | |
| tree | 5b34a7edafc482b89659100a27383abb748edfe5 /Documentation | |
| parent | fd6ec5d79507f99639c94f107e8a98550c9e1cf6 (diff) | |
w1: ds2438: support for writing to offset register
Added a sysfs entry to support writing to the offset register on page1.
This register is used to calibrate the chip canceling offset errors in the
current ADC. This means that, over time, reading the IAD register will not
return the correct current measurement, it will have an offset. Writing to
the offset register if the two's complement of the current register while
passing zero current to the load will calibrate the measurements. This
change was tested on real hardware and it was able to calibrate the chip
correctly.
Signed-off-by: Luiz Sampaio <sampaio.ime@gmail.com>
Link: https://lore.kernel.org/r/20210519223046.13798-7-sampaio.ime@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/stable/sysfs-driver-w1_ds2438 | 7 | ||||
| -rw-r--r-- | Documentation/w1/slaves/w1_ds2438.rst | 11 |
2 files changed, 17 insertions, 1 deletions
diff --git a/Documentation/ABI/stable/sysfs-driver-w1_ds2438 b/Documentation/ABI/stable/sysfs-driver-w1_ds2438 index fa47437c11d9..d2e7681cc287 100644 --- a/Documentation/ABI/stable/sysfs-driver-w1_ds2438 +++ b/Documentation/ABI/stable/sysfs-driver-w1_ds2438 @@ -4,3 +4,10 @@ Contact: Luiz Sampaio <sampaio.ime@gmail.com> Description: read the contents of the page1 of the DS2438 see Documentation/w1/slaves/w1_ds2438.rst for detailed information Users: any user space application which wants to communicate with DS2438 + +What: /sys/bus/w1/devices/.../offset +Date: April 2021 +Contact: Luiz Sampaio <sampaio.ime@gmail.com> +Description: write the contents to the offset register of the DS2438 + see Documentation/w1/slaves/w1_ds2438.rst for detailed information +Users: any user space application which wants to communicate with DS2438 diff --git a/Documentation/w1/slaves/w1_ds2438.rst b/Documentation/w1/slaves/w1_ds2438.rst index ac8d0d4b0d0e..5c5573991351 100644 --- a/Documentation/w1/slaves/w1_ds2438.rst +++ b/Documentation/w1/slaves/w1_ds2438.rst @@ -22,7 +22,7 @@ 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): +except "iad" and "offset" are readonly): "iad" ----- @@ -52,6 +52,15 @@ 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. +"offset" +------- +This file controls the 2-byte Offset Register of the chip. +Writing a 2-byte value will change the Offset Register, which changes the +current measurement done by the chip. Changing this register to the two's complement +of the current register while forcing zero current through the load will calibrate +the chip, canceling offset errors in the current ADC. + + "temperature" ------------- Opening and reading this file initiates the CONVERT_T (temperature conversion) |