[Elecraft] Advice needed: Remote Station Enhancement

[Don Wilhelm]

I believe that logic can quickly merge into the idea that "the first to 
introduce BCD Band Data" will "set the standard".  I for one do not 
believe that is the best approach, and certainly not sufficient to 'set 
a standard', which may have serious flaws when extended beyond that 
manufacturer's realm.

The Yaesu method (I cannot call it a standard) will inter-operate with 
other Yaesu gear and 3rd party gear designed to inter-operate with it, 
but that does not constitute a "standard"

The "standard" for data communication has been established in the 
digital world for many, many years, and pre-dates the Yaesu system.

Drivers do not source voltage (they use open collector and open drain 
devices), and there is one pullup resistor at the end of the signal line 
- there may be multiple receivers monitoring the signal line, but there 
can be only one driver active at a time - which for a multiple driver 
situation means an external source of control is necessary for gating 
the drivers.
I was working with those "rules" when designing computer console 
circuits for a IBM large system back in 1969, and the same principals 
had been devised since the advent of IBM SLT logic modules in the late 
1950s.

So if anyone wants to apply "the first guy sets the standard", I think 
Yaesu was not the first, but they made the mistake of having the drivers 
source voltage.  That is only practical for very short signal lines and 
a very limited number of receivers listening on the signal line(s).

Efforts to continue the "Yaesu method" will result in further confusion 
as amateur box to box communications develops further and more and more 
incorporates design principles previously applied to computer systems 
and communications lines.  Even the IBM terminal communications plugged 
the "pullup" resistors at only one terminal (they were called line 
terminators) - at the end of the communications line.  That is a long 
established principle that works even today if done right.  What I am 
saying is that Yaesu did not "do it right" and creates limitations to 
expansion and the advancement of technology within the amateur community 
today.

So get out the cutters and remove the collector and drain resistors from 
the Yaesu drivers, and put pullup resistors only at the far end of the 
lines, and you can have the Yaesu "system" without any of the problems.

There are other systems that do allow multiple drivers on the same 
signalling line(s) - I2C is one example - whichever driver grabs the 
signalling first gets priority is a simplified version of the operation. 
  Ethernet is another example, but in any of these systems, the protocol 
must define which driver gets priority.  That requires a bit more 
sophistication than a simple driver on the communication line.

I believe the original K3 "did it right" to use open drain drivers on 
the band data lines - but succumbed to the hue and cry that it did not 
work with the various versions of the Yaesu system and Elecraft then 
added pullup resistors to the drivers.
The result has been a bastardized "system" that in many cases requires 
the addition of steering diodes and/or the removal of pullup resistors 
from external devices to make it work right.

73,
Don W3FPR

On 3/2/2018 6:17 PM, Joe Subich, W4TV wrote:
> 
>> As far as older Yaesu transceivers are concerned, their design is 
>> proprietary and cannot be brought into the mold without serious
>> converters (which should frankly be easily constructed by the serious
>> amateur).
> Yaesu's transceivers were the *first* to use BCD "band data".  As such,
> it should be incumbent on anyone using that interface to be electrically
> compatible with Yaesu's interface (source +5/+12V for logic high, open
> circuit for logic low).  Even the amateur DOS based logging software
> that provided "band data" on a computer LPT port duplicated that
> interface.
>