Re: Firecracker and USB-Serial

[isw <isw@xxxxxxxxxxx>]

In article <i925vs$o50$1@xxxxxxxxxxxxxxxxxxxxxxxxxx>,
 "petem" <petem001@xxxxxxxxx> wrote:

> "isw" <isw@xxxxxxxxxxx> a écrit dans le message de groupe de discussion :
> isw-DA72EE.21034411102010@[216.168.3.50]...
> > In trying to get this combination to work on my Mac with heyu, I've
> > discovered that DTR is never going high. With a 'scope, I can see the
> > "1" signal on RTS pulsing merrily, but the "0" signal on DTR never
> > moves. Which probably explains why the Firecracker isn't working...
> >
> > Can anyone shed any light on this problem? I understand that some
> > USB-Serial adapters won't work with the Firecracker, but I never was
> > able to find out precisely why (though there seemed to be an assumption
> > that it had to do with "low signal levels"). That is not the case here
> > -- the signal on RTS swings a full 5 volts.
> >
>
> Dont know if the firecracker need more then 5 volt, but if I am right the
> voltage for rs232 are supposed to be -12 to +12 volts..not 0 to 5 volts.

The spec does not specify voltages, only ranges. And there is a "legal"
method for making 0 and +5V work just fine. A problem *could* arise if
one end of the link assiduously adhered to the +/- 12 volt swing *plus*
the rarely used hysteresis offset, while the other end used 0/+5.

Isaac