Found this:

http://home.kpn.nl/thomas_7/1Wire/1wire_isolating.html

Putting a driver after the DS2482-x00 give more reliability for long lines?

Nico


Ivan Lisenkov wrote:
> Now I am using DS9490R, but it is very unreliable. I now I have 6 
> DS18B20, 2 D2406, DS2408 and 2 DS2438. The network is about 50m long 
> (twisted pair, UTP-5). I can say, that DS9490R is totally not suitable 
> for me. Devices appear and disappear randomly, same device appears 
> multiple times, sometimes it is impossible to read or write a value. 
> As I added one DS2438 more, network became unusable.
>
> It will be great if DS2482-x00 will be more reliable in long networks. 
> I'll try to build adapter provided by Patryk and test it this week.
>
>
> Best Regards,
>
> Ivan, PhD
>
>
> On Mon, Apr 23, 2012 at 1:25 PM, Chris Lautre 
> <chris.lau...@karusoft.com <mailto: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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