Re: [stella] compact send-only serial subroutine

Subject: Re: [stella] compact send-only serial subroutine
From: Mark De Smet <de-smet@xxxxxxxxxxxxxxx>
Date: Fri, 12 Aug 2005 23:04:26 -0400
 > --- Fred Quimby <c9r@xxxxxxxxxxx> wrote:
 >>As for a cable, I would think that you'd just need
 >>to connect two wires:

Glenn Saunders wrote:

> Wouldn't something like these would be necessary for
> the TTL level conversion:

Correct.  RS232 serial ports (the standard variety) signal with +/-12V 
logic(I think it is inverted so -12V corresponds to a 1)

+/-10V has been more common for quite a while, and almost all RS232 
chips inputs can take anything from +/-5V to +/-15V.  Common RS232 chips 
use a charge pump to generate the +/-10V from the system voltage, 
typically 5 or 3.3V.

Thus, TTL logic with +5 to 0V signaling will not work.(reliabily.  You 
may get it to work a little, but not reliably.)

Either of those products would be exactly what you need.  Just connect 
the tty level signal to the I/Os of the joystick port, and the power and 
grounds togather to power the chip.

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