[time-nuts] GPDSO is working

[Brian Alsop]

Hi Bob,

Here is my experience.  I had a PIC that output RS232 at 0-5 volt 
levels.  It actually worked with my computer directly.  When I added a 
MAX 232 to make the levels something like -10/+10 volts.  It didn't 
work.  That's because the MAX232 inverts the polarity.  Look at the data 
sheet, the level converters are clearly inverters.

The fix in my case was to invert the RS232 stream output by the PIC and 
all was fine.

I'm not sure exactly what you have but a scope sorts it out quickly.

73 de Brian/K3KO

On 7/13/2013 01:12, Bob Stewart wrote:
> Hi Brian,
>
> I don't understand.  Are you saying that I need to add still more parts to get an RS-232 to TTL adapter to work?  Here's the circuit for what I'm currently using, and it looks like it's inverter based.  I'm not using it, because it's the only one I have and I want to keep it available for other use.
>
> http://www.scienceprog.com/wp-content/uploads/2006i/RS232_ALT/interface_schematic.gif
>
> Bob - AE6RV
>
>
>
>
>
>> ________________________________
>> From: Brian Alsop <alsopb at nc.rr.com>
>> To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
>> Sent: Friday, July 12, 2013 7:36 PM
>> Subject: Re: [time-nuts] GPDSO is working
>>
>>
>> Max 232's invert the polarity.  You have to follow with an inverting
>> gate if the TTL stuff worked.
>>
>> Brian
>>
>>
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