Hello,
I use my BeagleBord Black to monitor my heating-system.
I use DS18S20 as temperature sensors.
In the moment there are 7 sensors connected but I need more of them. The 1-wire bus supports only 10.
How can I have an other pin as a 1-wire-bus-master ?
BTW: I describe my system on my webpage: http://www.powershell.pub/ds18b20/
It is in German language…
Thank you
Robert
Unfortunately, I don’t read German so I couldn’t read the description of your project.
The 1-wire bus will support much more than 10 devices. I’m not sure where that information originated. The only real limitations, other than software, would be power supply and bus length/capacitance. If you’re powering the devices parasitically you will likely need an external pass transistor to provide power during conversions. The sensors require 1.5 mA each during conversion.
I’m not sure how the drivers are implemented on the BBB, but I presume they are bit-banging a port pin. Probably not the best way to do it…
If it were me, I would interface to the 1-wire bus with one of the handy interface devices available from Maxim. The DS2482-100 and DS2482-800 are I2C to 1-wire and I2C to 1-wire X 8 interfaces respectively. They also have a UART to 1-wire, the DS2480B. Also there is a USB to 1-wire dongle (DS2490R) which works quite nicely. I’m not sure what the deal is with Linux drivers, though.
That should have read “DS9490R” not “DS2490R”…
Thanks for your answer.
My project goes only about a software solution to put all the data into an mysql and draw nice pictures with it J
The BeagleBoard has already an software device driver for w1 but this is imitated to 10 slaves per master and I have found somebody who talks about multiple w1-master-pins on one board but nobody writes an article how to configure it.
The DS2482 series work really well, letting it manage the 1-wire bus (or 8 of them for the -800 version) and communicating with it via I2C is a good strategy and very easy to implement in software. Here’s an old blog post about doing this with an Atmel NGW100:
http://www.dgmo.org/1-wirecircuits
The author made the Eagle files available for the circuit he built:
http://randomtechmakings.blogspot.com/2009/07/belated-files.html
You could easily adapt this to a BBB cape, in fact there’s even a breakout board for this:
http://www.inmojo.com/store/inmojo-market/item/1-wire-driver-ds2482-800/