> No, not so, Gene. As already pointed out, RS485 is the multipoint > > version of RS422, so balanced enough to pass a "walk the dotted line" > > DUI test. ;-) Seriously, the 'A' and 'B' balanced line labels can be > > seen on the PCB at the above link. > > If the above link= > <http://www.ebay.com/itm/2PCS-MAX485-Module-RS-485-Module- > TTL-to-RS-485-Converter-For-Arduino/131694536431?_trksid= > p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo% > 3DSIC.MBE%26ao%3D2%26asc%3D40130%26meid%3De519e5e6252c4e40b7d0fa2b19dc > d5fc%26pid%3D100005%26rk%3D6%26rkt%3D6%26mehot%3Dag%26sd%3D112076449800> > > Yes, I see that now. That I assume means its half-duplex, but the spi is > too. > > Thats a great price. There is also this 5 pack available: > <http://www.ebay.com/itm/5-MAX485-Module-RS485-Module- > TTL-to-RS-485-Module-Converter-Board-TS/172176974958?_trksid=p2047675. > c100005.m1851&_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao% > 3D2%26asc%3D40130%26meid%3D23e1633c0ba04d319d14c7ad895c > f7e1%26pid%3D100005%26rk%3D1%26rkt%3D6%26sd%3D13169453> > > Now, do we have an hm2 driver for the pi's gpio? > > And in one of the adds it mentions slew rate limited, so I wonder what > its top speed is? >
The 585 is "limited slew rate" so as to minimize EMI. This limits speed to about 250K buad Other version of the chip with different numbers can go to about 10X faster 2.5M baud but then you are sending square waves down a wire and radiating the bits into space. Twist the pairs and shield it. I pointed out that product on eBay as an example of what you can get. Just about ANYTHING is available on a little breakout board for a price close enough to free that you should not care. (yes 50 cents or free, it is about the same thing) Just use normal RS422 drivers. You can find those too. Search eBay based on the MAX chip part number. Br sure to read the data sheet for the chips involved. These Chinese vendors know NOTHING about what they are selling. The vendors are typically some guy working out of his apartment. > > And if that slew rate is in the form of a capacitor, could it be removed? > > Has anyone here used this one? What for & how fast? > > Since this stuff is best described as volatile, I'll buy the 5 pack so > I've some to "play with". > > Lots of questions... > > ... > > > > > And its data rate must be pretty slow, its slew rated but not in any > > > usefull way. > > > > Ah, yes, the MAX485 will limit you to 2.5 Mb/s, and tolerance of > > "improperly terminated cables" isn't something we'd need. The jabber > > about "reduced EMI" sounds dubious too, as properly terminated twisted > > pair ought not radiate alarmingly. > > > > > > People are using Cat5 (Ethernet cable) for all types of serial > > > > links now. It just works better as most links are now balanced > > > > pairs. > > > > Yes, a reel of that stuff is buried somewhere in any good components > > stash, I hold. > > > > Erik > > > > ---------------------------------------------------------------------- > >-------- Check out the vibrant tech community on one of the world's > > most engaging tech sites, Slashdot.org! http://sdm.link/slashdot > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > Genes Web page <http://geneslinuxbox.net:6309/gene> > > ------------------------------------------------------------ > ------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
