robert@uop.UUCP (Robert McCaul--The Equalizer) (07/23/87)
the other day i was musing over something that had me abit angry a few months back... even with the prices plummeting, would it be cheaper to build a modem? where would i go about getting parts? i have lots of chip catalogs that list such things as modem chips.. but would it really be worth it? just curious, as this 300 baud beastie is *real* slow... i thought a fun project would be to throw a modem together on a weekend or two... please send e-mail, i will summarize if there is enough interest. "He reads all the time....is that healthy??" ...sun!ptsfa!cogent!uop!robert ...seismo!lll-crg!ucdavis!uop!robert
larry@kitty.UUCP (Larry Lippman) (07/23/87)
In article <426@uop.UUCP>, robert@uop.UUCP (Robert McCaul--The Equalizer) writes: > even with the prices plummeting, would it be cheaper to build a > modem? It might be theoretically cheaper in component cost, but you would spend a hell of a lot of time doing it. > where would i go about getting parts? > i have lots of chip catalogs that list such things as modem chips.. Assuming that you want an "auto-dial" modem, there is much more to the modem that the actual modem IC. You need a DTMF or rotary-pulse dialer, call progress tone detection, telephone line interface, and logic to handle commands and do dialing. This logic is much too complex to perform with discrete components, so it requires a microprocessor - like an 8051. As an example, consider the Silicon Systems SSI-K212 modem IC. This IC comes out with a microprocessor data bus interface - so it MUST be used with a microprocessor. While this IC has a built-in DTMF dialer and call progress tone detector, it has no telephone line interface, and still requires a rotary dial pulsing circuit. As I see it, writing the microprocessor code to make this IC work is not a trivial task. I would guess that you would require at least 500 lines of 8051 code to emulate a Hayes modem command set. > but would it really be worth it? In my opinion, no. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rocksanne|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
rex@otto.COM (Rex Jolliff) (07/28/87)
Summary: Expires: Sender: Followup-To: Distribution: Keywords: In article <426@uop.UUCP> robert@uop.UUCP writes: >the other day i was musing over something that had me abit >angry a few months back... > >even with the prices plummeting, would it be cheaper to build a >modem? > >where would i go about getting parts? If I remember correctly, there was a curcuit cellar article in an issue of BYTE magazine several months ago that talked about this axact thing. He didn't actually discuss the construction of the modem because it was too simple. The modem only used one chip! I believe the chip was called 'MOSART' or something like that. It did some amazing things according to the article, like detecting busy/disconnected/ring signals, and even direct control of A/D and D/A converters connected to the audio channel(I think). The article made this chip sound like it had everything but the kitchen sink. If you wnat the name of the company and you can't find the right mag., let me know and I'll dig it out of my pile of old bytes. Rex -- Rex Jolliff (rex@otto.UUCP, {akgua,ihnp4,mirror,sdcrdcf}!otto!rex) The Sun Newspaper - |Disclaimer: The opinions and comments in Nevada's Largest Daily Morning | this article are my own and in no way Newspaper | reflect the opinions of my employers. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - What happened to our superior space program?