we've had great success using a max202. 16-pin IC, w/ integral chgpump
converter,
requires 5 0.1uF caps, & will handle the xmit/recv translation. you tie
the rs232 i/o directly to the pins of a 9-pin DSUB (don't have the pin
#'s devoted to memory.)

Jason Sachs
Electrical Engineer

Deka Research & Development
340 Commercial Street
Manchester, NH 03101
(603) 669 5139 x327

> -----Original Message-----
> From: Istvan, Retaller [SMTP:ha5bwh@HA5KFU.SCH.BME.HU]
> Sent: Thursday, April 23, 1998 12:25 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      RS232 PC-PIC
>
> Message-Id: 14080_ha5kfu
> From: ha5bwh@ha5kfu.#bp.hun.euro (Istvan, Retaller)
> To: piclist@mitvma.mit.edu
>
> Ints Mikelsons asks:
>
> Have anybody tried to connect PIC to PC COM port directly? How does
>
> schematic look like?
>
>
>
> Hi,
>
> I built a few different boards connecting PIC to PC. Unfortunately I'm
>
> unable to remember where the info came, but it says, PC's RS32 is of a
>
> "shifted-zero" level port, which means you can drive it with TTL
> levels.
>
> For the PIC input port I used to connect a 22k...100k serial resistor
>
> to limit incoming level swing to appropriate level. You may forget
>
> clamping diodes, because PIC's input diodes handle this problem.
>
> For PIC output I use another serial resistor, value is about 100 ohms.
>
> This is just save PIC against accidental shorts sometimes I make
>
> during my job.
>
> It was not tested at a lot of PC-s, but I'm sure, 15-20 PC's already
>
> worked this way quite correctly.
>
>                                    Istvan