Searching \ for 'Request for info on PIC <--> RS232 interfacing.' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/microchip/ios.htm?key=rs232
Search entire site for: 'Request for info on PIC <--> RS232 interfacing.'.

Truncated match.
PICList Thread
'Request for info on PIC <--> RS232 interfacing.'
1995\05\19@100227 by Chris Madden

flavicon
face
RS232 interfacing made easy.

What you need:
--------------
               1. MAX232 / MAX233

Why you need:
-------------
               1. VOLTAGE LEVEL CONVERSION
                  -------------------------
                  The MAX232/3 acts as a voltage level converter.
                   It converts the 0/5V TTL level of the PIC to
                   +12/-12V level of the RS232 target system.
                  The MAX232 employs a charge pump to achieve the
                   larger voltage. The charge pump requires external
                   resistors / capacitors for the MAX232.
                  The MAX233 has these resistors / capacitors on chip &
                   therefore offers a SINGLE CHIP TTL <--> RS232 VOLTAGE
                   LEVEL CONVERTER.

What you need to know:
----------------------
               The MAX232/3 contains two receive & two transmit buffers
                (ie you can convert two different TTL signals to RS232 &
                two different RS232 signals to TTL).
               For a bare-bones-up-and-running-quickly implementation
                you need only one transmit and one receive buffer.
               For handshaking (if it's necessary) the spare transmit and
                receive buffer can be used for CLEAR_TO_SEND (CTS) and
                REQUEST_TO_SEND (RTS) signals.
                Using these spare buffers in this way will improve
                 communication reliability.


Example (My first attempt at ascii art!) :
--------
BARE-BONES-UP-AND-RUNNNG-QUICKLY IMPLEMENTATION:


       [RS232:+12/-12V]                              [TTL:0/5V]
                            MAX232/3                      PIC
                               ___                        ___
                                |   +5V                    |   +5V
                            ---------                   -------
                           |         |          RB0    |       |
       TARGET TX           |   |\    |          PIC RX |       |
               ________\___|___| \___|__\______________|       |_____
                       /   |   | /   |  /              |       |     |
                           |   |/    |                 |       |    ----
                           |         |          RB1    |       |    ||||
       TARGET RX           |    /|   |          PIC TX |       |    ----
               ________/___|___/ |___|__/______________|       |_____|
                       \   |   \ |   |  \              |       | crystal
                           |    \|   |                 |       |
                           |         |                 |       |
                            ---------                   -------
                                |                           |
                                |      Ground              ----
                              ----                         \  /
                              \  /                          \/
                               \/


       TARGET GROUND                                   PIC GROUND

                 _______________________________________
                |                                       |
                |                                       |
              ----                                     ----
              \  /                                     \  /
               \/                                       \/

The PIC exteranal interrupt pin may be used to signal the receipt of a START
bit. The remaining bits are then received in software from this pin.


Where to find out more:
-----------------------
               1. PIC AN510 application note: "implementation of an
                  asynchronous Serial I/O" at various PIC ftp sites.
               2. Serial communications FAQs:
            http://www.paranoia.com/~filipg/HTML/LINK/PORTS/F_Parallel.html




       Take Care,
               Chris Madden


1995\05\19@121750 by Paul Greenwood

flavicon
face
> RS232 interfacing made easy.
>
> What you need:
> --------------
>                 1. MAX232 / MAX233

Anyone know of a solution like this that allows you to tri-state the RS232
outputs?  (The +/-12V side - NOT the TTL side.)

--
           -- Paul Greenwood --  (spam_OUTpabloTakeThisOuTspamaustin.ibm.com)
For an idea to be fashionable is ominous, since it must afterwards be
always old-fashioned.

"His super power is to turn into a scotch terrier."

1995\05\20@182158 by Timothy McDonough DIAL UP1

flavicon
face
Some of the Linear Technology RS232 transcievers let you externally
shut down the chip, I don't recall if it puts the inputs and outputs
in a high-Z state.

On Fri, 19 May 1995, Paul Greenwood wrote:

{Quote hidden}

1995\05\21@173840 by Doug Sellner

flavicon
face
>> RS232 interfacing made easy.
>>
>> What you need:
>> --------------
>>                 1. MAX232 / MAX233
>
>Anyone know of a solution like this that allows you to tri-state the RS232
>outputs?  (The +/-12V side - NOT the TTL side.)
>
>--
>            -- Paul Greenwood --  (pablospamKILLspamaustin.ibm.com)
>For an idea to be fashionable is ominous, since it must afterwards be
>always old-fashioned.
>
>"His super power is to turn into a scotch terrier."


I'm no expert but I might try using a diode to turn the RS232 Level to
pullup only and use a terminating resistor to pull the line low at the end
of your chain of devices.

Doug Sellner
Beach Tech
4131 Vincent Avenue South
Minneapolis MN 55410

Voice (612) 924-9193 x 521
Fax   (612) 926-1145

Internet: .....dsellnerKILLspamspam.....embay.com

More... (looser matching)
- Last day of these posts
- In 1995 , 1996 only
- Today
- New search...