HWCTRL.THD --- Copyright 1987 by Phil Wheeler An original compilation of Compuserve Model 100 Forum messages for use by Forum members only. This thread file has two basic, but related, topics. One is use of the Model 100 as a TDD device for the deaf by use of the cassette port (software control of the connections at that port). The other theme is oriented to more general applications of the Model 100 for hardware control, using the RS-232 port. Message range: 152244 to 152539 Dates: 7/9/87 to 7/13/87 TDD Model use of the Model 100 ------------------------------ Sb: #TDD Modem in the M100 Fm: Martin Zimmerman 72757,3076 To: Bob Andersen 70526,1233 Great news! I browsed around the rest of this system and found that there exists some programs for the IBM and the COCO that emulate a TDD modem via thier casstte port. After doing some research on the Model 100 hardware, I have found that the cassette port can be controled 100% from software. Since the TDD is a half duplex device, the computer is NEVER recieving AND transmitting at the same time, this is the capability of the cassette port on the Model 100. The mark and space frequencies are 1200 and 1400 Hz for a TDD modem, and the one that the M100 uses for cassette I/O are 1200 and 2400 Hz. By peeking at the ROM routines that generate these frequencies I can modify them to generate the TDD frequencies. The ROM already has a routine for determining the frequency of a wave-form at the cassette port, so recieving is a simple task. It now looks as though the only harware needed will be an adapter for acoutic cups to a cassette cable or a direct-connection adapter from the cassette port to the phone-line. In the direct connect case, the cassette relay could be used to pulse dial... If we go the acoustic cup connection, then the harware cost of the ENTIRE project is in the under $5.00 range. Not bad for a modem, eh? Camz. Fm: Bob Andersen 70526,1233 To: Martin Zimmerman 72757,3076 A nice piece of work! Would appreciate hearing from you when it is operational. Regards, Bob A. Fm: bob scott 73125,1437 To: Martin Zimmerman 72757,3076 I may be able to help you out. I wrote a dialer routine for the cassette port for an Aussie sig memeber who had a "crippled" export M100 (no dial routines). Only hardware was a 15 cent 600 ohm resistor. bob Fm: Martin Zimmerman 72757,3076 To: bob scott 73125,1437 Great stuff! I think I have to get the Modem software written in the meantime, but when I go to add the dialer bit... I'll get back to you! Thanks! Camz. Fm: Bob Andersen 70526,1233 To: Martin Zimmerman 72757,3076 Interestingly enough, two weeks ago I had disassembled DATAW (Tech. Ref. Manual P.88) at address 6F5B(hex) in order to use the cassette port to generate a sequence of 1 Khz pulse bursts for a test fixture. In order to avoid jitter due to the 4msec clock tics, I ran my routine with interupts disabled. Calculating the frequecies based on a clock of 4.9152 Mhz and 14 T states per software tic, I concur that the frequencies used by the cassette routines are 1200 and 2400 Hz. A possible fly in the ointment is the fact that discriminate between 1200 and 1400 Hz in the presence of telephone line noise is a much more severe requirement than discriminating between 1200 and 2400 Hz assuming a cassette recorder with relatively low noise. In my opinion this translates to a system with poor noise immunity, which is what we might expect from an ultra low cost modem. It may still be worth tracking down the Exar chips in order to compare performance of the two systems. What do you think? Fm: Martin Zimmerman 72757,3076 To: Bob Andersen 70526,1233 True enough. They have done this trick with IBM's and COCO's, I might download the info file on that and see what they say about noise, an Camz. Hardware Control with the Model 100 ----------------------------------- Sb: #hardware control Fm: Jon Payne 76576,2713 To: [F] All I am looking for a controller board to operate some equipment as programmed by the m100. It should plug into the rs232 port and be capable of both receiving input and sending output. Any ideas? Fm: Wayne Day 76703,376 To: Jon Payne 76576,2713 I've forwarded your message to ALL in the hopes that other folks might see it and be able to help you out a bit... You might check through the back issues of BYTE magazine for two things.. ads from companies that do process control equipment (which sounds like basically what you're looking for) as well as articles from Steve Ciarcia's Circuit Cellar. Steve is a homebrewer of the 1st class, and some of his past articles might be what you need. Fm: Ran Talbott 70506,60 To: Jon Payne 76576,2713 Sibec, Single Board Systems, and MicroMint (Steve Ciarcia) all sell small single-board computers based on various micros. All have ads in Byte, as do others whose names escape me at the moment. Some units are based on chips with built-in BASIC interpreters. Another possibility is a MultiBus CPU board. THere are lots of them on the surplus market, and many of them come with one or 2 serial and parallel ports. MultiBus chassis can be had pretty cheaply (as a matter of fact, I'll give you a steal of a deal on one if you're in the San Jose area). This would require some sort of development system for assembling code and burning EPROMs, though.