Don't forget, that the I²C bus-master can drive much less capacity load on
cable (I measured a max of only 8,9nF which represent about 89m IY(ST)Y
cable)
The USB bus-master based with DS9490R is able to drive 28nF - so
theoretically about 280m cable

On Mon, Apr 23, 2012 at 11:25, Chris Lautre <chris.lau...@karusoft.com>wrote:

>
> I would be very interested in a USB to 1Wire Hub with 8 1 Wire ports.
> This would eb much better than using multiple  DS9490R.
>
> Chris
>
>
> On 22/04/2012 10:42, Patryk wrote:
> > I propose a new USB 1-wire adapter.
> > The DS2490 native USB 1-wire adapter is no longer in production. I think
> > you can still buy built adapters from Hobbyboards but if You want to
> build
> > your own it's nearly impossible to source this chip. The popular solution
> > is to use DS2480B with some serial to USB converter like FT232 it behaves
> > then like native DS2490.  However if one plans to have w big 1-wire
> > network with multiple branches the better way seems be DS2482-800 which
> is
> > basically a 1-wire master with one bus  connected to a 8 port hub. You
> can
> > have then a star topology. Again You can still(not sure) buy a hub from
> > Hobbyborad to achieve the same goal but the hub chip is also out of
> > production. So if you are familiar with soldering iron this is a solution
> > for you.
> >
> > The DS2482-800 uses I2C bus. The conversion form I2C to USB is handled by
> > Atmega8A  which is a 8 bit microcontroller and runs a special program.
> > It's a very popular chip it costs about $2(at least in Poland). However
> > You have to upload the firmware to it for which you need a programmer. If
> > you don't have one but you have an old PC with parallel port you can
> build
> > one with few resistors and a plug. Also Raspberry Pi can program AVR
> chips.
> > First I run i2c-tiny-usb
> > http://www.harbaum.org/till/i2c_tiny_usb/index.shtml on Atmega8
> > but there was a performance issue. The read from DS18B20 took about 3
> > seconds
> > and without specifying the bus about 10. Compared to 1.5 with DS2480 and
> > similar
> > time connected to vga i2c port.
> > Fortunately there is a derivative project from Till's i2-usb-tiny it's
> > called OSFI(Open Source InterFace) . It's part of a project called
> > OpenServo http://www.openservo.com/StepByStep
> > It uses Atemga8 and has better performance because it uses some built in
> > i2c(do not know exactly).
> >
> > Here is the whole circuit. I think it's pretty explanatory. For testing
> > You can omit the voltage regulator and power it directly from USB and not
> > using the diodes should be fine for most computers. I done my prototype
> on
> > a breadboard and it works fine.
> > http://ubuntuone.com/6uM1yQRB36zgGEFDxrTc7c
> >
> >
> > On the 1-wire side DS9503 are not essential to get it running they just
> > protect the bus from electrostatic discharges. However they are cheap. I
> > used RJ-12 connectors (telephone) There are different standard's of
> wiring
> > the additional +5V the RJ45 are also popular. You can use screw
> connectors
> > as well. I think I will use 4 RJ45 for longer cables and if more power is
> > needed and  RJ12 for thermometers.
> >
> > After assembling it on a breadboard You have to program the uC the
> > firmware can be downloaded from OpenServo cvs.
> >
> http://www.openservo.com/viewcvs/OpenServo/Interfaces/OpenServo_InterFace/driver/Version_2/firmware/?root=cvs
> > You need main.hex
> > avrdude -c usbasp -p atmega8 -U lfuse:w:0x9f:m -U hfuse:w:0xc9:m -U
> > flash:w:main.hex
> >
> > Then you can test if it's recognized by the system
> > lsusb shows
> > Bus 001 Device 005: ID 1964:0001
> > There is no name for it
> >
> > Then you have to compile kernel module
> >
> http://www.openservo.com/viewcvs/OpenServo/Interfaces/OpenServo_InterFace/driver/Version_2/kernel/?root=cvs
> > make
> > sudo make install
> > sudo depmod -a
> >
> > sudo modprobe osif
> >
> > sudo modprobe i2c-dev
> >
> > then
> > sudo i2cdetect -l
> > should show something like this
> > i2c-0 i2c             OSIF at bus 001 device 005              I2C adapter
> >
> > Then you can run owfs
> > sudo owfs –i2c=/dev/i2c-0 /mnt/owfs
> > You can also use the parameter
> > --i2c=ALL:ALL  and owfs will look at every i2c device. However there is
> > some bug in older version an you might get segmentation fault. It is now
> > fixed in CVS
> >
> > The you should get something like this
> > sudo ls /mnt/owfs
> > bus.0
> > bus.1
> > bus.2
> > bus.3
> > bus.4
> > bus.5
> > bus.6
> > bus.7
> > settings
> > structure
> > uncached
> > statistics
> > system
> >
> > Here's the whole Eagle project the board is half done
> > http://ubuntuone.com/32tUJtqRyNr3ngTsApwW83
> > and how it looks like on a breadboard
> > http://ubuntuone.com/0CUuACUSJMW69aK2FznM6i
> >
> >
> > Pleas give tips how to improve this tutorial. The board is on the way.
> >
>
>
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