Hi, I'm in the thick of designing my test rig. It is now over 350 points mixed between thermocouples and 18b20s. I decided on 3 buses with ds2482-100s to handle this. These and some other things (I2C drivers and power) I need will sit on a beaglebone cape. Everything will be running at 3.3V
I am designing a little board to handle the 8 thermocouples using max31850s and will also have 8 rj45s to handle 18b20s soldered onto the end of ethernet cable. There is power and ground and a data in and out to keep the bus topology. Because I don't know how many will be 18b20s connected, I am putting a dip switch that will allow the bus to bypass open rj45s. This got me thinking about how long a stub I can have running from the bus to the actual device. I know an inch on a board trace is fine, but how long a stub can I get away with and still have the bus being happy? I am wondering if the rj45 cable is 1-2 feet long, could I just leave the switch shorted and plug the cable in? I'm not planning to run it this way, but I was thinking in the case where a configuration changes and someone forgets to open the switch when they plug the cable in. While I'm at it, do people put a pull up resistor on the end of their buses? I haven't done so in the past but am wondering with a setup that really can't fail. If so, what value should it be? I'd just solder a resistor on the end of a stub of ethernet cable then shrink wrap it. thanks, jerry ------------------------------------------------------------------------------ Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server from Actuate! Instantly Supercharge Your Business Reports and Dashboards with Interactivity, Sharing, Native Excel Exports, App Integration & more Get technology previously reserved for billion-dollar corporations, FREE http://pubads.g.doubleclick.net/gampad/clk?id=157005751&iu=/4140/ostg.clktrk _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
