Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-lcc!ames!pasteur!ucbvax!PCO-MULTICS.HBI.HONEYWELL.COM!Albert From: Albert@PCO-MULTICS.HBI.HONEYWELL.COM Newsgroups: comp.sys.atari.8bit Subject: Re: Serial Interface Message-ID: <881216034421.553809@PCO-MULTICS.HBI.HONEYWELL.COM> Date: 16 Dec 88 03:44:00 GMT Sender: daemon@ucbvax.BERKELEY.EDU Reply-To: Albert%pco@CIM-VAX.HONEYWELL.COM Organization: The Internet Lines: 72 This is being entered for someone who does not have direct access to the net. Reply to me or the list and I will forward, or contact Paul directly. -------------------------- REGARDING THE MESSAGE AT Date: 20 Nov 88 20:23:01 GMT From: killer!netsys!c3pe!charles@ames.arc.nasa.gov (Charles Green) Subject: Re: Serial Interface In 1982 I wanted to build a serial port for my ATARI but didn't have much money, so I investigated building one. Fortunately, I worked for a company that had an agreement to build hardware for ATARI CORP. so I had a complete (preliminary) copy of what became the Technical Reference Manual. I designed and built the hardware, and software drivers, and terminal emulator (complete with XMODEM file transfers) for a "mainly software" serial port. It had 2 ports, hardware/software busy and baud rates of 0-9600 baud. (Due to the clock frequency of the ATARI, the margin of error at 19200 baud was a little too big). The hardware consisted of 3 chips and an external power supply. Today it could be done with 2 chips and no external supply using the MAX-232. On of ATARI's best kept secrets was not so much the fact that the POKEY chip had a serial port built in, but the fact that it was a full standard ASYNC port! There were two problems: 1. The data was TTL not RS-232. 2. When diskette (or other intelligent device) I/O was performed, the serial port needed to be told not to listen. Problem 1 was easy enough. As was stated earlier the voltage-level translation is easily done with the MAX-232 chip. At the time however this chip was not available, so I used the readily available 1488/1489 combination along with a -12v supply. The +12v was available from the SIO connector, and I added the -12v with a $2.95 DC wall transformer (came from an old calculator). Problem 2 was a little more difficult. At first I tried using the cassette motor control line and had no problem telling the serial port to listen. I did have a problem telling the port to NOT listen. It seems that the motor control line decayed too slowly after turning off. It was meant for a device that drew more current than my tri-state buffer was using. After a lot of thought, I decided there was no alternative, so I went ahead and used one joystick port to give me the extra hand-shaking signals that I needed. This also gave me enough signals to add a second serial port along with hardware busy for both ports! Well to make an even longer story a little shorter, I got it completely working, built a few prototypes, and had dreams of getting rich marketing it. (At the time the only game in town was the ATARI 850 at about $175). Needless to say, this didn't happen, and I still use one of my prototypes. I noticed several references to building an ATARI serial port including erroneous data, so I thought that if anyone is interested I will dig this all out of my archives and make it available. If anyone is interested, I will make available the following: 1. Complete Hardware schematics. 2. Software driver including source for two serial ports configured as P:, and R: (user changeable). 3. Terminal emulator capable of 110-9600 baud, user selects type of busy i.e. Hardware/XON XOFF Just send me a blank diskette and a SASE with enough postage to accomodate the bundle. Or, just send $5 and I will send it all to you. Or if you send me three blank disks and a SASE with postage I will include the source for the terminal emulator. Or send me $10 and I'll send you everything above with all the source. It shouldn't cost much more than about $15 in parts to build the hardware. (THE SOFTWARE AND SCHEMATIC ARE NOT PUBLIC DOMAIN THEY ARE ALL COPYRIGHT 1983 PAUL M. WALTERS) My mailing (U.S. mail) address is: Paul M. Walters 1140 N. Higley suite 109-310 Mesa, AZ 85205