>-----Original Message-----
>From: Mark Mynsted [mailto:mmynsted_news@GBRONLINE.COM]
>Sent: 16 April 2004 06:05
>To: PICLIST@MITVMA.MIT.EDU
>Subject: [EE:]TTL to/ From rs232 for 16F628 circuit
>
>
>I am new to this and want to be able to connect my circuit to
>my pc to provide nice informaiton for debugging etc.  The
>16F628 has a AUSART but I need to alter the voltage. I found
>the following here at piclist:
>http://www.piclist.com/techref/io/serial/ttl->rs232.htm
>
>TTL
>To/From rs232
>http://www.botkin.org/dale/rs232_interface.htm
>
>This looks great, but has anybody else used this?  I thought
>that MOSFETs were really sensitive to ESD.  I really like the
>low cost, few parts, and no electrolitics.  (In case I want to
>later embed in potting
>resin.)
>
>Also I could not find the exact MOSFETs he shows.  Locally I
>can get NTE semiconductors from FRYs (at high cost) but I am
>not sure if their NTE491 is really the same.  Is it close
>enough to work? http://www.nteinc.com/specs/400to499/NTE491.html
>
>(I may get these from Dale's site but I would rather get the
>parts now, and not use paypal.)


Nice low component count, but this circuit does not produce the negative
voltages specified for RS232.  In that respect it's not much better than a
simple transistor inverter working off the PIC's supply rail.

Personaly I tend to use one of the Maxim drivers with the built in caps.
They are a little expensive, but the convienience factors outweighs that for
me by a large margin.  Unless you are making thousands of a very low cost
product where every cent/penny counts, then I would tend towards a solution
that you know is going to be reliable and work under all conditions.

Regards

Mike




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