Emax

Indeed, the SN pin connections you mentioned are correct - this means that only on the two MAX485 the + and - signals should be swapped.
Once modified I would expect that there's a big chance the circuit should work, even without any resistors and capacitors.

Except for the LED resistors and the signal shaping capacitors C4 and C5 on the EmuSer schema, the other resistors and capacitors are mainly added for signal leveling/protection purposes (avoiding too high voltages on input pins and avoiding peaks). But in normal circumstances - given the voltage range specifications of all involved ICs (the absolute maximums and the tresholds for L and H) - direct connections between the ICs should work too... I would have to double check but I think this is true both for the ICs and Teensy you have used, and the ones that are used in the EMuSer schema.
I remember though that I had problems with alternative designs with more or less resistors on the board, so I decided to stick as much as possible to the original design by Julian H (co-member of this forum). 

It will be interesting to learn about any possible differences between the two schemas !

///E-Synthesist




--- In emax@yahoogroups.com, "Adam" <fake@...> wrote:
>
> First of all, thank you for caring!
> 
> i had the idea, that on the MAX'es the +/- things should be swapped.
> but why on the SN?
> 
> In the meantime i've ordered the original ICs you used from the US, because i could see these nowhere around. I'll definietly going to compare these part by part, and will let you know if we found out something!
> 
> thanks,
> 
> adam
> 
> --- In emax@yahoogroups.com, "esynthesist" <esynthesist@> wrote:
> >
> > I just did a quick comparison of the ICs you used with the ones as specified for the EmuSer. At first sight they should be compatible, although yours are a bit slower...
> > 
> > However when checking your connections mentioned in your message below, I think you have swapped the inverting and non-inverting pins.
> > I think the RXD+/RXD- and TXD+/TXD- must be swapped on the MAX and SN ICs...
> > 
> > ///E-Synthesist
> > 
> > --- In emax@yahoogroups.com, "Adam" <fake@> wrote:
> > >
> > > well, it starts to make sense! it really looked disappointing, now there are new things to check. 
> > > 
> > > meanwhile i switched to an Emulator II+HD to do the tests, because i know that works well with SD thru DB25. is it fair to assume that it has a healthy port and will work with the EMXP too?
> > > 
> > > i put this back to the bench and will check if there were any signals coming in and out on the TX-RX stuff. i havent included the LEDs on this design.
> > > 
> > > since the UA9637AC is not available around, i replaced it. i did not use any capacitors and resistors though. i assume you used it to shape the signal (apart from those to support the LEDs). if there were any other reasons, please let me know, i need to check that.
> > > 
> > > i am going to list the short description of my version in a very easy way. everything is connected direct, no resistors or capacitors used. please see below if you were interested in.
> > > 
> > > "So, what error do you actually get in EMXP ?   "
> > > 
> > > When receiving from the EII it says: Errorcode 990. There is a communication problem with the EII. ReasonCode is 3.
> > > 
> > > i am going to post it quick, so maybe you had more time to check and think, and now i'll return to measure the circuitry.
> > > 
> > > and now the connections:
> > > 
> > > 
> > > 
> > > RECEIVER (RX): MAX RS485
> > > ---------------------
> > > TXD+ (Emax: pin8) -> Teensy RXD+ (RS422:3) -> RS485:7 (B)
> > > TXD- (Emax:pin9) -> Teensy RXD- (RS422:4) -> RS485:6 (A)
> > > GND (Emax:pin3) -> Teensy (RS422:5) -> RS485:5 (GND) 
> > > RS485:pin1 (R0) -> Teensy PD2 (RXD1)
> > > RS485:pin2 (NRE) -> L 
> > > RS485:pin3 (D) -> L  
> > > RS485:pin4 (DI) ->  not connected 
> > > 
> > > TRANSCIVER (TX): MAX RS485
> > > ------------------------
> > > Teensy TXD (PD3) -> RS485:pin4 (DI)
> > > RS485:pin6 (A) -> Emax:pin5 (RXD-)
> > > RS485:pin7 (B) -> Emax:pin4 (RXD+)
> > > RS485:1 (R0) -> not connected
> > > RS485:2 (NRE) ->H
> > > RS485:3 (DE) ->H
> > > 
> > > CLOCK (CLK): SN75176B
> > > ------------------------
> > > CLK (Emax:5) -> SN75176B Pin6 (A) 
> > > SN75176B:pin7: B -> L
> > > SN75176B:pin1: R -> Teensy PD5  (XCK)
> > > SN75176B:pin4 (D) -> not connected
> > > SN75176B:pin3 (DE) -> L 
> > > SN75176B:pin2 (NRE) -> L
> > >
> >
>