ÒÓ-232 ÉÎÔÅÒÆÁÃÉÎÇ ÔÏ ÔÈÅ ÕÓÅÒ ÐÏÒÔ

                                  ÂY ÄOUG ÒEED

(ÁUTHOR'S NOTE: THIS PUBLIC DOMAIN ARTICLE WAS FIRST PRINTED IN THE ÅL-ÓHIFT-ÏH NEWSLETTER, ÁUGUST, 1985. ÉT IS BEING RELEASED TO THE NETS DUE TO THE AVID INTEREST IN ÒÓ-232 MODEMS. ÓOME CHANGES HAVE BEEN MADE FOR COMPLETENESS.)


     ÔHE ÖÉÃ-20, Ã-64, AND Ã-128 ARE EXTREMELY VERSATILE MACHINES IF THE USER HAS THE MEANS AND DETERMINATION TO USE THEM. ÔHE USER PORT CAN BE USED AS A PARALLEL OUTPUT PORT, OR AS AN ÒÓ-232 PORT. ÏUR SCHEME IS TO UTILIZE THE ÒÓ-232.
     ÃOMMODORE HAS, RATHER THAN USE A SPECIALIZED COMMUNICATIONS CHIP AS MOST COMPUTERS USE, CHOSEN TO CONTROL ALL ÒÓ-232 FUNCTIONS USING A STANDARD 6522 ÖERSATILE ÉNTERFACE ÁDAPTER (ÖÉÁ) FOR THE ÖÉÃ, OR 6526 ÃOMPLEX ÉNTERFACE ÁDAPTER (ÃÉÁ) FOR THE 64, AS WELL AS SOME COMPLEX BUILT-IN SOFTWARE. ÔHIS IS NOT WITHOUT LIMITATIONS, MAINLY SPEED, DUE TO THE ÃÐÕ TAKING CARE OF SO MANY HOUSEHOLD TASKS, SUCH AS SCREEN UPDATING, UPDATING JIFFY CLOCKS, ETC. 1200 BAUD IS ABOUT THE MOST THE Ã-64 CAN HANDLE, AND WITH SOME PROGRAMS IT DOESN'T DO THIS SO GOOD. ØMODEM7.3 HAS WORKED ABOUT THE BEST FOR ME (INCLUDING ÖIDTEX).
     ÔO USE THE ÒÓ-232 PORT, YOU MUST USE A SIMPLE HARDWARE INTERFACE BETWEEN THE Ã-64 AND THE ÒÓ-232 DEVICE. ÁS YOU MAY KNOW, ÔÔÌ USES VOLTAGE LEVELS OF APPROXIMATELY Ï-1 VOLTS TO REPRESENT A LOGIC Ï AND 3-4.5 VOLTS TO REPRESENT A LOGIC 1. ×ELL, ÒÓ-232 USES -3 TO -15 VOLTS AS A '1' AND +3 TO +15 AS A 'Ï'. ÁND, AS YOU MAY HAVE FIGURED OUT BY NOW, ÁÌÌ OF THE CHIPS IN THE ÖÉÃ AND 64 ARE ÔÔÌ COMPATABLE, WHICH IS A NOT SO MARVELOUS WAY OF SAYING THEY'RE NOT ÒÓ-232 COMPATABLE. ÉF THIS WEREN'T ENOUGH, OUR FRIENDS AT THE BIG Ã WERE SOMEHOW ABLE TO COMPLICATE MATTERS BY INVERTING SOME OF THESE SIGNALS.
      ÓO, OUR PROBLEM IS TO SHIFT THE COMPUTER'S ÔÔÌ OUTPUT LEVELS TO A STANDARD ÒÓ-232 LEVEL. ÓINCE THE ÖÉÃ-1Ï11Á ÒÓ-232 CONVERTER CARTRIDGE IS SET UP FOR OUTPUTS TO A MODEM, THIS IS HOW THIS CIRCUIT IS SET UP. ÔHE ORIGINAL CIRCUIT COMES FROM THE ÁUGUST 1982 ISSUE OF ÃOMPUTE!. ÔHE ÃOMPUTE! CIRCUIT DID NOT TAKE INTO ACCOUNT THE INVERSION OF FIVE SIGNALS, BUT THESE ARE PROVIDED HERE WITH THE 74Ï4.
      ÔHIS CIRCUIT WORKS WITH A MODEM AS IS, AND NEXT MONTH É WILL HAVE AN ARTICLE TO CONSTRUCT A NULL MODEM ADAPTER SO THAT YOU MAY USE A ÒÓ-232 PRINTER WITH THIS CIRCUIT.
      É ASSUME THAT IF YOU ARE REALLY INTERESTED IN THIS LITTLE PROJECT THAT YOU ALREADY KNOW HOW TO DO SOME ELECTRONIC CONSTRUCTION. ÔHE PARTS WILL TOTAL AROUND TWENTY DOLLARS (LIST), AND YOU PROBABLY ALREADY HAVE SOME IN YOUR SCROUNGE BOX THAT YOU CAN USE. ÔHE ONLY HARD TO FIND PART IS THE CONNECTOR BETWEEN THE BOARD AND THE USER PORT. ÉT IS A 12/24 PIN CONNECTOR WITH .156 INCH LEAD SPACING. ÉF YOU GO TO A SURPLUS ELECTRONICS STORE, LOOK FOR THESE NUMBERS: '5Ï 24Á 3Ï' AND/OR '251 12 3Ï 16Ï'. ÙOU CAN EXPECT TO PAY ABOUT TWO BUCKS ON THIS ONE. ÁN ALTERNATE SOURCE IS ÄIGI-ËEY, PH. 800-344-4539, PART # Ã1-12, $2.90 PLUS $2.00 SERVICE CHARGE. ÔHIS PART WILL NEED SOME SURGERY AS THE CIRCUIT BOARD WILL BE THINNER THAN THE CONNECTOR. ÔRY SOLDERING ALL OF THE PINS ON ONE SIDE OF THE CONNECTOR, THEN BEND THE OTHER SIDE'S PINS DOWN TO THE CIRCUIT BOARD. ÎOW SOLDER THESE. ÙOU'LL ALSO NEED A ÄÂ-25 FEMALE CIRCUIT BOARD CONNECTOR OF EITHER THE SOLDER OR WIRE-WRAP VARIETY, DEPENDING ON HOW YOU GO ABOUT YOUR CONSTRUCTION. ÔHIS AND ALL OTHER PARTS SHOULD BE AVAILABLE AT YOUR LOCAL ÒADIO ÓHACK (TELL THEM THEY'RE FOR YOUR ÃOMMODORE). É HIGHLY RECOMMEND USING SOCKETS FOR THE THREE ÉÃS FOR TWO REASONS: 1) YOU CAN DO ALL YOUR WIRING WITHOUT DAMAGING THE ÉÃS, AND 2) IF YOU HAVE AN ÉÃ GO BAD, IT WILL BE EASIER TO REPLACE.

                                   ÐARTS ÌIST

     1 - 74Ï4 (ÒADIO ÓHACK #276-18Ï2)
     1 - 75188 OR ÍÃ1488 (#276-252Ï)
     1 - 75189 OR ÍÃ1489 (#276-2521)
     3 - 1Î4ÏÏ1 DIODES (#276-11Ï1)
     3 - 47UÆ, 16Ö CAPACITORS (#272-1Ï27)
     1 - 1ÏUÆ, 16Ö CAPACITOR (#272-1Ï25)
     4 - 1Ï KOHM, .25× RESISTORS (#271-1335)
     1 - CIRCUIT BOARD (É RECOMMEND ÒADIO
         ÓHACK'S #276-154 3 VOLTAGE BOARD.)

€*JU1
     É THINK THAT MOST OF THE WIRING IS STRAIGHTÀFORWARD FROM THE DIAGRAM. ÓOME ITEMS THAT SHOULD BE MENTIONED:
€*JU0;
     1) Ã1 IS THE 1Ï UÆ CAPACITOR.
     2) Ã2 - Ã4 ARE THE 47 UÆ CAPACITORS.
     3) ÇROUND IS CONNECTED TO:
          74Ï4  - PIN 7
          75188 - PIN 7
          75189 - PIN 7
     4) +5Ö IS CONNECTED TO:
          74Ï4  - PIN 14
          75189 - PIN 14
     5) +ÖÃÃ IS CONNECTED TO: 75188 - PIN 14
     6) -ÖÃÃ IS CONNECTED TO: 75188 - PIN 1
     7) ÃONNECT ONE SIDE OF EACH OF THE RE-
        SISTORS TO +5Ö. ÃONNECT THE OTHER
        SIDE INDIVIDUALLY TO THE 75189 AT
        PINS 2, 5, 9, AND 12.
€*JU1;
     ÃHECK WITH AN OHMMETER THAT THE +ÖÃÃ, -ÖÃÃ, +5Ö, AND GROUND LINES ARE NOT SHORTED TO EACH OTHER BEFORE YOU PLUG IT INTO YOUR COMPUTER. ÉF YOU HAVE MADE NO WIRING ERRORS, IT SHOULD WORK FINE WITH ANY ÒÓ232 MODEM. ÇOOD LUCK.