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Rockbox mail archiveSubject: Re: AW: JB not starting with remote pin connected ?Re: AW: JB not starting with remote pin connected ?
From: <Matthias.Klumpp_at_gmx.de>
Date: Wed, 23 Jun 2004 20:52:18 +0200 (MEST) Hi Sophana, > >I had a more close look to the signal. In fact there is a short send > command > > > that's probably your problem Not probably, it IS my problem ;-)) > >If you apply 5V direct to the remote input of the JB, there were no > >damages? > > > I use a 10k pull up resistor. applying 5v through a resistor will never > damage your device, since it is protected by clamping transistors for > electrostatic protection. > Very often, 3.3v devices are made direct compatible with 5v devices by > using special transistors on the positive side. Hmmmmm...... > >Ah, so my low level of 0,7V is maybe too close to Vil, that might cause > >communication problems in some models....... > >I think, I should modify that OC stage to soemthing that has a real 0V > >low state.... > > > the more you will be close to the voltage limit, the less your design > will be tolerant to noise induced by several environemental factors. > But it can work that way. I once did a test with a JBR of a friend of mine who bought it at Ebay. The remote was not working, but I'm not sure if it was due to a connection problem or maybe exactly because of the low level passing beyond TTL's 0,8V level..... In my JB Studio I don't have problems at all. > >What do you think would be better: > >- Simply connecting the UART 5V directly to the remote pin (without OC > >stage > >at all) ? > > > This can work and I even think it is the best and simplest solution. > Simply place a 2k to 10k resistor for protection between both pins. > Do you use bidirectionnal communication? > If not there will be no problem at all since there is only 1 transmitter > so no electrical conflict. > If yes, collisions (if any) will be protected by the resistor you will > place between both outputs. > > >- Designing a double npn transistor stage with last trans. as "real" OC ? > > > If you want a "real" open collector this is the solution indeed. But a > lot of components: 3 resistors + 2 transistors. > This is only needed if you absolutly want to have a real low level > during collisions of 2 transmissions. > Some protocols need that low level. > You don't need it here... I'll think about it.... THX Matthias -- ---------------------------------------------------------------------- Sent by: Matthias Klumpp E-Mail : Matthias.Klumpp_at_gmx.de ---------------------------------------------------------------------- ACHTUNG : Diese E-Mailbox wird nur einmal wöchentlich gelesen ! ATTENTION: This E-Mail account is read only once a week ! ATENCAO : Este box e-mail será lido apenas uma vez por semana ! ---------------------------------------------------------------------- +++ Jetzt WLAN-Router für alle DSL-Einsteiger und Wechsler +++ GMX DSL-Powertarife zudem 3 Monate gratis* http://www.gmx.net/dsl _______________________________________________ http://cool.haxx.se/mailman/listinfo/rockboxReceived on 2004-06-23 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |