Hello all, I found out that I connected the ground wire to the wrong part! There are two regulators on the board, each connected to a (separated) galvanic isolated output of the powersupply :-(
So, I'll have to do my homework again! But thanks for all your help. Connecting the ground wire and still having trouble (as described above) resulted to some ground bounce in my head, messing up my reference ;-) Kind regards, Elbert Smit. > -----Original Message----- > From: da Silva, Joe [mailto:[EMAIL PROTECTED]] > Sent: dinsdag 24 september 2002 3:49 > To: Multiple recipients of list CHIPDIR-L > Subject: RE: Strange LTC485 behavior > > > The bus should be connected as a "daisy-chain" (ie. no "star" > connections), with a terminating resistor at each end (ie. > two resistors in total). > > A 2V swing is *more* than enough! Your problem is either a > common-mode problem (if you read the standard, it says you > need a common potential/connection between all the nodes, if > you want this stuff to actually work properly), as suggested > by some of the others. The other possibility is noise > pick-up, which you might be missing if your CRO timebase is too long. > > Joe. > > > -----Original Message----- > > From: Peter Vogel [SMTP:[EMAIL PROTECTED]] > > Sent: Friday, September 20, 2002 9:48 AM > > To: Multiple recipients of list CHIPDIR-L > > Subject: Re: Strange LTC485 behavior > > > > Are you terminating the lines at one end or at both ends? My > > recollection is that they should be terminated at one end only. > > > > On Thu, 19 Sep 2002 03:53:29 -0800 > > Elbert Smit <[EMAIL PROTECTED]> wrote: > > > > > Hello Chipdir members, > > > > > > We are using LTC485 RS-485 transceivers and found some strange > > > behavior. > > > > > > > > We have a test setup with two devices, one using a Sipex > RS232/RS485 > > > (selectable) transceiver in a industrial PC, and one of our own > > > devices, using the LTC485. > > > > > > These two devices will only communicate if we remove the > termination > > > resistor of 120 ohm at one side, leaving the bus unterminated. > > > > > > When the resistor is placed, the voltage swing of the A and B > > > channel is still about 2 Volt, which should be > sufficient, according > > > to the RS-485 documentation I have. Only differences > below 200mV are > > > undefined. > > However, > > > the 2 Volt voltage is not enough to operate for some of > the devices. > > > We tried several LTC485's and found out that some of them worked > > > fine with termination, but some didn't. Testcable length is an > > > awsome 50 cm ;-) > > > > > > Any ideas or clues? > > > > > > Kind regards, > > > > > > Elbert Smit > > > -- > > > Author: Elbert Smit > > > INET: [EMAIL PROTECTED] > > > > > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > > San Diego, California -- Mailing list and web hosting services > > -------------------------------------------------------------------- > > - > > To REMOVE yourself from this mailing list, send an E-Mail message > > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > > the message BODY, include a line containing: UNSUB CHIPDIR-L > > (or the name of mailing list you want to be removed from). You may > > also send the HELP command for other information (like subscribing). > > > -- > Author: Peter Vogel > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB CHIPDIR-L (or the > name of mailing list you want to be removed from). You may also send > the HELP command for other information (like subscribing). -- Author: da Silva, Joe INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Author: Elbert Smit INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
