On 1/5/2012 11:36 AM, Jan-Erik Soderholm wrote:
>
> Charles Craft wrote 2012-01-05 17:02:
>   =20
>> What happens if you only connect the grounds - no TX ->   RX connection?
>> I think your going to need something (resistor?) between the PIC and a
>> RS-232 pin.
>>     =20
> No, one need a proper RS232/TTL-CMOS converter, such as MAX232.
> And since he has one (right?), this is a non-issue.
>
>   =20

Nice to have but not a must have.
Google "rs-232 ttl transistor" and look at the schematic images.
Somewhere around here I've got a temperature sensor built into a DB-25=20
shell running a PIC that's powered by DTR.
A diode, 2950 LDO regulator, couple resistors and a transistor to drive=20
the transmit line.
No room or power available for a MAX-232 chip. Works just fine on=20
laptops and a Sun server.

chuckc

--=20
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