NOTE: Since Linux-v4.15-rc1, this driver is included in the mainline kernel.



w1_ds28e17 README

This document describes the w1_ds28e17 Linux kernel driver, how to build it,
how to use it with a DS28E17 chip, what the limitations are.

Author: Jan Kandziora <[email protected]>

=== Table of Contents

	=== 1  Introduction
	=== 2  Understanding the DS28E17
	   --- 2.1  Operation
	   --- 2.2  Limitations
	      +++ 2.2.1  Speed
	      +++ 2.2.2  I2C protocol
	      +++ 2.2.3  Host adapters
	   --- 2.3  Interfacing the DS28E17 with a 5V Onewire bus and/or 5V I2C device
	=== 3  Building the driver
	   --- 3.1  Obtaining the w1_ds28e17 driver sources
	   --- 3.2  Patching the driver into an existing kernel source tree
	      +++ 3.2.1  Preparing the kernel sources
	      +++ 3.2.2  Configuring the kernel sources
	      +++ 3.2.3  Rebuilding the "wire" driver module
	      +++ 3.2.4  Building the "w1_ds28e17" driver module
	      +++ 3.2.5  Installing the "wire" and "w1_ds28e17" driver modules
	      +++ 3.2.6  Building and installing additional driver modules
	      +++ 3.2.7  Updating module dependencies
	=== 4  Using the driver
	   --- 4.1  Loading the driver
	      +++ 4.1.1  Driver Parameters
	   --- 4.2  Sysfs properties
	   --- 4.3  Setting up UDEV
	   --- 4.4  Playing with the DS28E17 evaluation kit
	=== 5  Reporting bugs and problems
	=== 6  License


=== 1  Introduction

The Onewire bus is a slow, 15kBaud bus system which can form extensive networks
of hundreds of metres of a one-wire (plus ground) cable, with dozens of slave
devices attached to it. Onewire slave devices usually are single chips or small
circuits only and they are used to monitor temperatures, pressures, battery
charging, and to control remote single-bit inputs and outputs.

The Linux kernel has a "w1" subsystem which allows to connect various kinds of
Onewire host adapters to the computer, including the USB-based ds2490, the I2C
based DS2482 and DS2483 families, and bitbanging the Onewire protocol through a
single GPIO port. The "w1" subsystem also supports various Onewire slave
devices such as thermosensor devices, PIO switches and battery monitors. In
addition, it allows userspace programs such as the "owfs" suite to access and
control the Onewire and perform more complicated functions.

The DS28E17 is a special Onewire slave device which acts as an I2C master
residing on the Onewire bus. It "tunnels" I2C through onewire, integrating your
I2C devices into a Onewire network and thus, allows you to create a "remote I2C
device" with little effort.

This w1_ds28e17 kernel driver makes all the I2C buses offered by the
Onewire-attached DS28E17 chips accessible through the usual kernel structures
and userspace tools. The support is transparent, the new I2C buses aren't much
different from the ones your computer has built in, apart from some minor
limitations introduced by the Onewire bus and the DS28E17 itself.


=== 2  Understanding the DS28E17

First, find the authoritative information about the DS28E17 on
Dallas Semiconductor/Maxim Integrated's website:

https://www.maximintegrated.com/en/products/interface/controllers-expanders/DS28E17.html


There's of course more to say about that. There are a lot of pesky details the
datasheet doesn't describe. And consequences for designing DS28E17 based
circuits and user software.


--- 2.1  Operation

The DS28E17 controls the I2C autonomously, unburdening the host to do so
itself. This includes bus arbitration, Start Condition, slave addressing,
sending out the buffered data at configured I2C speed, and finally Stop
Condition. Same for receiving data. It hands over data from one bus to another
through a 255 byte RAM buffer, first receiving all the data from one side, then
sending it on the other. During the I2C transfer, the Onewire communication
stops and vice versa.

A typical transfer is like this:
-------------------------------------------------------------------------------
Starting on Onewire. The Onewire host writes the following.

"Bus Reset"                             ____ (480µs low)
"Presence Pulse"                        ____ (>200µs low) (issued by all slaves)
"Match ROM" bus command                 0x55
DS28E17 slave address                   0x19 0x00 0x00 0x00 0x02 0xDB 0xD8 0x7B
"Write Data with Stop" device command   0x4B
I2C slave address (<<1 | R/-W bit)      0x90 (write to 0x48, a DS7505)
Write length                            0x03 (register number plus two data bytes)
Write data                              0x02 0x17 0x00 (DS28E17 buffers this)
CRC16 (0x4B 0x90 0x03 0x02 0x17 0x00)   0x9E 0x2D (little endian, inverted)

DS28E17 turns over to I2C while Onewire is left high. All the following is sent
by the DS28E17 autonomously. The host driver in the meantime does a usleep,
calculated from the I2C bus speed and number of bytes to send/receive on I2C.
After that lower bound, it actively monitors the Onewire line for end of
transfer condition.

Start condition                         SDA goes low while SCL is high
I2C slave address (<<1 | R/-W bit)      0x90 (write to 0x48, a DS7505)
Write data                              0x02 0x17 0x00
Stop condition                          SDA goes high while SCL is high

DS28E17 waits for a read time slot from the Onewire host to signal the end of
I2C transfer. After that, the Onewire host then reads the following from the
DS28E17.

Transfer status                         0x00 (ok)
Unacknowledged writes                   0x00 (none, ok)

End of Onewire transfer. Onewire stays high until next "Bus Reset".
-------------------------------------------------------------------------------


--- 2.2  Limitations

+++ 2.2.1  Speed

First thing you have to understand is Onewire is designed to be a *reliable but
slow* bus system. It only has a bit rate of approximately 15kBaud. Though the
DS28E17 supports the Onewire "overdrive" mode (roughly 77kBaud), the kernel's
"w1" subsystem doesn't and that "overdrive" mode only works reliably with very
small Onewire networks, rendering it pretty much useless for creating "remote
I2C slave devices". So, take it as set you have to stick to 15kBaud speed. In
addition to this, you can see from the above there is a lot of protocol
overhead on the Onewire side.

To transfer 3 bytes to an I2C slave —which could be done in 60µs on a host
connected 400kBaud I2C— you need about 11,000µs on the DS28E17. (It would
be still 2,200µs at the unimplemented overdrive speed.)

It should be clear that this is only acceptable for small data amounts such as
coming from temperature and pressure sensors or seldomly accessed devices such
as remote single-bit inputs and outputs driving switches, solenoids and such.
For bigger amounts of data like reading a kilobyte chunk of data stored in a
1Mbit I2C eeprom M24M01 you need a different solution (but then, accessing it
in small chunks may be sufficient for your application.)

Placing another DS2482 (or DS2483) I2C to Onewire host adapter chip behind a
DS28E17 is, while technically possible, unadviseable for the same reason. The
protocol overhead doesn't double but it is squared!

You should also recognize the Onewire protocol requires the host to process
a lot of data in a timely manner. Using a ds2490 based host adapter offloads
that and will improve your host's overall performance, while using a simple
GPIO for bitbanging the Onewire protocol will create a lot of interrupts and/or
busy looping and thus, load.


+++ 2.2.2  I2C protocol

The second limitation is about the I2C protocol the DS28E17 is able to produce.
It does so autonomously and there is no way to produce arbitrary I2C protocol
elements, let alone SDA/SCL signal combinations with the DS28E17.

The DS28E17 is able to produce the following I2C sequences:
-------------------------------------------------------------------------------
Write Data with Stop:      S Addr Wr [A]  Data [A] Data [A] ... [A] Data  [A] P
Write Data no Stop:        S Addr Wr [A]  Data [A] Data [A] ... [A] Data  [A]
Write Data only:                          Data [A] Data [A] ... [A] Data  [A]
Write Data only with Stop:                Data [A] Data [A] ... [A] Data  [A] P
Read Data with Stop:       S Addr Rd [A] [Data] A [Data] A  ...  A [Data] NA  P

Key to symbols

S     (1 bit) : Start bit
P     (1 bit) : Stop bit
Rd/Wr (1 bit) : Read/Write bit. Rd equals 1, Wr equals 0.
A, NA (1 bit) : Accept and reverse accept bit.
Addr  (7 bits): I2C 7 bit address. Note that this can be expanded as usual to
                get a 10 bit I2C address.
[..]: Data sent by I2C device, as opposed to data sent by the host adapter.
-------------------------------------------------------------------------------
This list is exhaustive. The amount of data sent or received with one Onewire
command is limited to 1..255 bytes. For the read sequences, the amount of data
to be read from the I2C slave device must be determined by the host. 

(For the curious: the DS28E17 also has a combined command "Write, Read Data
with Stop" which produces less Onewire protocol overhead than the equivalent
"Write Data no Stop", "Read Data with Stop" sequence. The w1_ds28e17 driver
uses that special command automatically when possible.)


This puts three further limitations to the I2C and SMBus on the DS28E17:

There is no "Read Data without Stop". So, there isn't a way to receive more
than 255 bytes in one transaction. The w1_ds28e17 driver ends the current
transaction with -EIO on an attempt to read more than 255 bytes.

Neither is there a way to turn around from read to write in one transaction.
The w1_ds28e17 driver issues a normal "Read Data with Stop", "Write Data" ...
sequence in that case. This should be fine when no other master operates on the
same I2C bus as the DS28E17.

Another limitation is the missing "Read Data only". The Onewire host always has
to announce the number of bytes to read from the I2C slave device in advance.
The w1_ds28e17 driver issues a normal one byte "Read Data with Stop", followed
by a "Read Data with Stop" with the number of bytes to read taken from the data
byte read in the first. Again, this should be fine when no other master
operates on the same I2C bus as the DS28E17.


+++ 2.2.3  Host adapters

The kernel's w1 subsystem only supports a small selection of available Onewire
host adapters. Most prominently, DS2480B and LINK based adapters are NOT
SUPPORTED, neither are ethernet based ones.

That's a pity, even the current evaluation kits from Maxim feature
such an unsupported DS2480B based adapter.


--- 2.3  Interfacing the DS28E17 with a 5V onewire bus and/or 5V I2C device

IMPORTANT! The DS28E17 is a 3.3V device. It isn't 5V tolerant. When you hook it
up to a 5V circuit it seems to be but once you accidentally lift the Vdd line
while the IO line is still attached, it's fried. Been there, seen that. [-_-;]


If you have to interface a 5V bus line to the DS28E17 (likely), use this
level-shifter circuit:

|
|        +5V ----.           ,-----+---- +3.3V
|                |           |     |
|                \         G |     \
|                /      –––––'     /
|                \    ––– – –––    \
|                |     |  ^  |     |
| 5V bus line ---+-----'  '--+-----+---- 3.3V bus line
|                      D     S
|

The transistor is a small signal N-channel enhancement mode MOSFET, e.g. a
2N7000, BS170 or MMBF170. The value of the two pullup resistors depend on the
pullup current you need, 1.5kΩ to 4.7kΩ is okay for most cases.

Use this circuit on both the SDA and SCL pin of the DS28E17 if you have to
interface 5V I2C devices (but check if they are 3.3V compliant first, many
are.)

Use this circuit on the IO pin of the DS28E17 when you have to interface a
standard 5V Onewire bus as with ds2490, ds2482, and ds2483 based host adapters
for example. You can leave out the 5V pullup in that case, there is one built
into the Onewire host adapter.


=== 3  Building the driver

Building the w1_ds28e17 driver unfortunately is *not* straightforward, as the
w1 subsystem needs to be patched to expose a function needed for operating the
DS28E17. It is still easy however.


--- 3.1  Obtaining the w1_ds28e17 driver sources

Get the w1_ds28e17 driver source archive from github.

[~]$ wget https://github.com/ianka/w1_ds28e17/archive/master.tar.gz -O w1_ds28e17.tar.gz

Unpack the driver sources into your home directory.

[~]$ tar -xf w1_ds28e17.tar.gz


--- 3.2  Patching into a kernel source tree

+++ 3.2.1  Preparing the kernel sources

First, you need matching kernel sources, the gcc compiler suite, make,
ncurses-devel etc. Read the manual of your Linux distribution on how to set all
this up. Assumed you have the kernel sources of your current kernel unpacked
at ~/linux-4.1.23/ and want to build the w1_ds28e17 driver for the running
kernel, do

[~]$ cd ~/linux-4.1.23

First you have to patch the existing "wire" driver sources inside your kernel
source tree.

[~/linux-4.1.23]$ patch -p1 <~/w1_ds28e17-master/w1.diff

Next step is to patch the Kconfig and Makefile inside drivers/w1/slaves to
enable the config options and build of the w1_ds28e17 driver.

[~/linux-4.1.23]$ patch -p1 <~/w1_ds28e17-master/Kconfig.diff
[~/linux-4.1.23]$ patch -p1 <~/w1_ds28e17-master/Makefile.diff

Last step is to copy the w1_ds28e17 driver source file into the kernel tree.

[~/linux-4.1.23]$ cp ~/w1_ds28e17-master/w1_ds28e17.c drivers/w1/slaves/

When all this succeeded you can configure the kernel sources.


+++ 3.2.2  Configuring the kernel sources

Start with the configuration of the running kernel.

[~/linux-4.1.23]$ zcat /proc/config.gz >.config

NOTICE: when you don't want to rebuild your whole kernel, make sure you aren't
turning anything from < > to <*>, <M> to <*> or vice versa. The only allowed
change is from < > to <M> then. Please note when "Device Drivers->Dallas's
1-wire support" was <*> at the very beginning, you have to rebuild your whole
kernel, install the new image it and reboot. That is because the basic "wire"
driver has to be patched for the "w1_ds28e17" driver to work.

Start the ncurses based configuration program.

[~/linux-4.1.23]$ make menuconfig

Check "Device Drivers->I2C Support". If you want your new DS28E17 based I2C
bus to be accessible from user space (likely), you also have to check "Device
Drivers->I2C Support->I2C device interface".

Check "Device Drivers->Dallas's 1-wire support".You may want "Device
Drivers->Dallas's 1-wire support->Userspace communication over connector" to be
switched on for making userspace tools like owfs to be able to access the
kernel's w1 subsystem.

Switch on "Device Drivers->Dallas's 1-wire support->1-wire Bus Masters" and the
host adapter you have:

Matrox G400           - unlikely you have this
DS2490 USB            - sold as DS9490 (blue conish USB plug)
Maxim DS2482          - for DS2483, too
Maxim DS1WM           - unlikely you have this
GPIO 1-wire busmaster - depends on "Device Drivers->GPIO support"

Switch on "Device Drivers->Dallas's 1-wire support->1-wire slaves
->1-wire-to-I2C master bridge (DS28E17)". This is the actual w1_ds28e17 driver.

Remember which modules you had to switch on, as you have to build and install
them later, too. Exit to top level and save your current kernel configuration
to ".config".


+++ 3.2.3  Rebuilding the "wire" driver module.

As written, the w1_ds28e17 driver needs another symbol to be exported from the
kernel's "wire" module. That is why you have to patch it (done above) and
rebuild it before building the actual w1_ds28e17 driver module you want.


NOTICE: You can always rebuild the whole kernel, and modules by doing
"make bzImage && make modules && make modules_install", and install and run
that. The following is just a shortcut procedure.


Prepare your kernel sources for rebuilding the modules. Build the wire.ko
module a first time to get the symversion line of the new w1_touch_bit symbol.

[~/linux-4.1.23]$ make modules_prepare
[~/linux-4.1.23]$ make drivers/w1/wire.ko
[~/linux-4.1.23]$ grep w1_touch_bit Module.symvers >Module.symvers.w1_touch_bit

Now rebuild wire.ko including both the default Module.symvers and the new
Module.symvers.w1_touch_bit. Most distributions save the Modules.symvers file
of their default kernel at the /boot directory. Look for that file if the zcat
line below fails.

[~/linux-4.1.23]$ zcat /boot/symvers-$(uname -r).gz | cat - Module.symvers.w1_touch_bit >Module.symvers
[~/linux-4.1.23]$ make SUBDIRS=drivers/w1 wire.ko


+++ 3.2.4  Building the "w1_ds28e17" driver module

From what you have prepared until now, building the w1_ds28e17 module finally
*is* straightforward. \[o_o]/

[~/linux-4.1.23]$ make SUBDIRS=drivers/w1/slaves w1_ds28e17.ko


+++ 3.2.5  Installing the "wire" and "w1_ds28e17" driver modules

Finally copy them to a location where the module tools can find them

[~/linux-4.1.23]$ sudo cp drivers/w1/wire.ko /lib/modules/$(uname -r)/kernel/drivers/w1/
[~/linux-4.1.23]$ sudo cp drivers/w1/slaves/w1_ds28e17.ko /lib/modules/$(uname -r)/kernel/drivers/w1/slaves/


IMPORTANT: *NEVER* use "make modules_install" when you followed these shortcut
instructions. That is because "make modules_install" will then *remove* all the
modules from /lib/modules/... but "wire" and "w1_ds28e17". If you do that, most
likely your system will not boot anymore.


+++ 3.2.6  Installing additional driver modules

This is straightforward as with the "w1_ds28e17" driver.

If you had to select the i2c subsystem, you now have to build and install the
driver modules selected.

[~/linux-4.1.23]$ make SUBDIRS=drivers/i2c i2c-core.ko i2c-dev.ko
[~/linux-4.1.23]$ sudo cp drivers/i2c/*.ko /lib/modules/$(uname -r)/kernel/drivers/i2c

If you had to select a Onewire host adapter driver, you now have to build and
install the driver modules selected.

[~/linux-4.1.23]$ make SUBDIRS=drivers/w1/masters
[~/linux-4.1.23]$ sudo cp drivers/w1/masters/*.ko /lib/modules/$(uname -r)/kernel/drivers/w1/masters


+++ 3.2.7  Updating module dependencies

A last step, you have to refresh the module dependencies file to make
"modprobe" work as expected.

[~/linux-4.1.23]$ sudo depmod -A



  _̣*_
\[o_o]/  Finally done with building and installing!
  [:]    You can use the driver now.
  / \



=== 4  Using the driver

--- 4.1  Loading the drivers

Please note nothing about the Onewire subsystem is autoloaded when you plug in
a device. You have to load the necessary drivers by hand.

First, load the "w1_ds28e17" driver module. This automatically loads the "wire"
and "i2c-core" drivers (the latter only if it's not built-in, which often is
the case.)

# modprobe w1_ds28e17

Then load a Onewire host adapter driver. If you have a DS9490R host adapter (the
blue conish usb plug), "ds2490" is the driver you need.

# modprobe ds2490

If you want to have userspace applications access the I2C devices connected to
your DS28E17 (likely), you need the "i2c-dev" driver, too.

# modprobe i2c-dev

Check the kernel log with

# dmesg | tail
...
usbcore: registered new interface driver DS9490R
w1_slave_driver 19-00000002dbd8: i2c speed set to 400 kBaud.
i2c /dev entries driver
#

All fine!


+++ 4.1.1  Driver Parameters

The "w1_ds28e17" driver has three global parameters, which can be passed from
the module tools (insmod command line or /etc/modprobe.d/ files) or the kernel
command line. These are:

speed:
	This sets up the default I2C speed a DS28E17 get configured for as soon
	it is connected. The power-on default	of the DS28E17 is 400kBaud, but chips
	may come and go on the Onewire bus without being de-powered and as soon
	the "w1_ds28e17" driver notices a freshly connected, or reconnected
	DS28E17 device on the Onewire bus, it will re-apply this setting.

	Valid values are 100, 400, 900 [kBaud]. Any other value means to leave alone
	the current DS28E17 setting on detect. The default value is 100.

stretch:
	This sets up the default stretch value used for freshly connected DS28E17
	devices. It is a multiplier used on the calculation of the busy wait time
	for an I2C transfer. This is to account for I2C slave devices which make
	heavy use of the I2C clock stretching feature and thus, the needed timeout
	cannot be pre-calculated correctly. As the w1_ds28e17 driver checks the
	DS28E17's busy flag in a loop after the precalculated wait time, it should be
	hardly needed to tweak this setting.

	Leave it at 1 unless you get ETIMEDOUT errors and a "w1_slave_driver
	19-00000002dbd8: busy timeout" in the kernel log.

	Valid values are 1 to 9. The default is 1.

Setting up parameters with insmod:

# insmod /lib/modules/$(uname -r)/kernel/drivers/w1/slaves/w1_ds28e17 speed=400
Setting up parameters for use with modprobe: create a file in /etc/modprobe.d/ containing

options w1_ds28e17 speed=400

Setting up parameters on the kernel command line (boot options).

... w1_ds28e17.speed=400 ...


--- 4.2  Sysfs properties

The kernel's w1 subsystem automatically creates a device subdirectory for any
Onewire slave connected to a host adaptor.

If your DS28E17 isn't detected in an instant, initiate a search by hand, then
reset to the default continous search.

# echo  1 >/sys/bus/w1/devices/w1_bus_master1/w1_master_search
# echo -1 >/sys/bus/w1/devices/w1_bus_master1/w1_master_search

For details, see Documentation/w1/w1.generic inside the kernel source tree.

# ls -l /sys/bus/w1/devices
total 0
lrwxrwxrwx 1 root root 0 Jul  9 20:03 19-00000002dbd8 -> ../../../devices/w1_bus_master1/19-00000002dbd8
lrwxrwxrwx 1 root root 0 Jul  9 20:03 81-0000002ce7cf -> ../../../devices/w1_bus_master1/81-0000002ce7cf
lrwxrwxrwx 1 root root 0 Jul  9 20:03 w1_bus_master1 -> ../../../devices/w1_bus_master1

The 19-nnn subdirectory contains the sysfs subtree of your DS28E17.

# ls -l /sys/bus/w1/devices/19-00000002dbd8/
total 0
lrwxrwxrwx 1 root root    0 Jul  9 20:03 driver -> ../../../bus/w1/drivers/w1_slave_driver
drwxr-xr-x 4 root root    0 Jul  9 20:03 i2c-5
-r--r--r-- 1 root root 4096 Jul  9 20:03 id
-r--r--r-- 1 root root 4096 Jul  9 20:03 name
drwxr-xr-x 2 root root    0 Jul  9 20:03 power
-rw-r--r-- 1 root root 4096 Jul  9 20:03 speed
-rw-r--r-- 1 root root 4096 Jul  9 20:03 stretch
lrwxrwxrwx 1 root root    0 Jul  9 20:03 subsystem -> ../../../bus/w1
-rw-r--r-- 1 root root 4096 Jul  9 20:03 uevent

driver, id, name, power, subsystem, and uevent are standard sysfs properties.

The speed and stretch values are the current settings of the parameters
described at section 4.1.1  Driver Parameters. You can tweak them individually
for each DS28E17.

i2c-5 is the name of the associated I2C master device node. If your udev daemon
is set up to handle I2C buses (likely), you can find the DS28E17 I2C bus char
device node at /dev/i2c-5 in that case. If you have more than one DS28E17
connected to your Onewire bus, each one gets its own char device node. Values
aren't fixed but may be enumerated differently between reboot, so it's
necessary to check for the actual char device name in this directory.

Or set up udev to create stable symlinks for each DS28E17 in your Onewire
network.


--- 4.3  Setting up UDEV

Create a file /etc/udev/rules.d/91-ds28e17.rules as follows:
-------------------------------------------------------------------------------
SUBSYSTEM=="i2c-dev", KERNEL=="i2c-[0-9]*", ATTRS{name}=="w1-19-*", \
        SYMLINK+="i2c-$attr{name}"
-------------------------------------------------------------------------------

Then reload the udev rules.

# udevadm control -R

After de-registering your DS28E17

# echo 19-00000002dbd8 >/sys/bus/w1/devices/w1_bus_master1/w1_master_remove

and initiating a search by hand, then resetting to the default continous search,

# echo  1 >/sys/bus/w1/devices/w1_bus_master1/w1_master_search
# echo -1 >/sys/bus/w1/devices/w1_bus_master1/w1_master_search

you get a nice, stable symlink

# ls -l /dev/i2c-*
crw------- 1 root root 89, 0 Jul  9 20:03 /dev/i2c-0
crw------- 1 root root 89, 1 Jul  9 20:03 /dev/i2c-1
crw------- 1 root root 89, 2 Jul  9 20:03 /dev/i2c-2
crw------- 1 root root 89, 3 Jul  9 20:03 /dev/i2c-3
crw------- 1 root root 89, 4 Jul  9 20:03 /dev/i2c-4
crw------- 1 root root 89, 5 Jul  9 23:24 /dev/i2c-5
lrwxrwxrwx 1 root root     5 Jul  9 23:24 /dev/i2c-w1-19-00000002dbd8 -> i2c-5

which is created from the factory id number of the DS28E17.


--- 4.4  Playing with the DS28E17 evaluation kit

The DS28E17 evaluation kit as offered from Maxim has a DS7505 I2C temperature
sensor chip on the same board as the DS28E17. You can play with that chip to
get a feeling how to deal with the DS28E17 and I2C. There are some sample
userspace test programs for the DS7505 chip in the driver source directory.

[~]$ cd w1_ds28e17-master
[~/w1_ds28e17-master]$ make
...
[~/w1_ds28e17-master]$ sudo ./ds7505-readtemp /dev/i2c-w1-19-00000002dbd8 0x48
22.500

Touch the chip, the temperature should increase.

[~/w1_ds28e17-master]$ sudo ./ds7505-readtemp /dev/i2c-w1-19-00000002dbd8 0x48
23.5000

Set up higher resolution and the thermostat trip points.

[~/w1_ds28e17-master]$ sudo ./ds7505-configure /dev/i2c-w1-19-00000002dbd8 0x48 0x60 24.5 23.0

Read configuration.

[~/w1_ds28e17-master]$ sudo ./ds7505-readconfig /dev/i2c-w1-19-00000002dbd8 0x48
0x60 24.5000 23.0000

Recall the configuration from EEPROM.

[~/w1_ds28e17-master]$ sudo ./ds7505-recall /dev/i2c-w1-19-00000002dbd8 0x48
[~/w1_ds28e17-master]$ sudo ./ds7505-readconfig /dev/i2c-w1-19-00000002dbd8 0x48
0x00 80.0000 75.0000

Change configuration again, store into EEPROM, reset, change, recall.

[~/w1_ds28e17-master]$ sudo ./ds7505-configure /dev/i2c-w1-19-00000002dbd8 0x48 0x60 24.5 23.0
[~/w1_ds28e17-master]$ sudo ./ds7505-store /dev/i2c-w1-19-00000002dbd8 0x48
[~/w1_ds28e17-master]$ sudo ./ds7505-reset /dev/i2c-w1-19-00000002dbd8 0x48
[~/w1_ds28e17-master]$ sudo ./ds7505-readconfig /dev/i2c-w1-19-00000002dbd8 0x48
0x60 24.5000 23.0000
[~/w1_ds28e17-master]$ sudo ./ds7505-configure /dev/i2c-w1-19-00000002dbd8 0x48 0x40 55 -10
[~/w1_ds28e17-master]$ sudo ./ds7505-readconfig /dev/i2c-w1-19-00000002dbd8 0x48
0x40 55.0000 -10.0000
[~/w1_ds28e17-master]$ sudo ./ds7505-recall /dev/i2c-w1-19-00000002dbd8 0x48
[~/w1_ds28e17-master]$ sudo ./ds7505-readconfig /dev/i2c-w1-19-00000002dbd8 0x48
0x60 24.5000 23.0000


=== 5  Reporting bugs and problems

There is not bounty on bugs but I think you are still as happy as I am to have
them fixed. So, if you encounter a bug, please report it.

If you encounter problems with building or using the w1_ds28e17 or the ds7505-*
test programs, feel free to contact me by email to [email protected]. Please provide
as much information as you can about your problem.


=== 6  License

The w1_ds28e17 Linux kernel driver is free software, written and copyrighted by
Jan Kandziora <[email protected]>. You may use, distribute and modify it under the
terms of the attached GPLv2 license. See the file COPYING for details.