pwong@batcomputer.tn.cornell.edu (Patrick Wong) (05/12/89)
Hi, guys,
The result is in ! Finally, instead of buying a standard rs-232 interface
for my c64, I bought a "COM-MODEM" adaptor for just under $25 (US) including
shipping. I use this adaptor to interface between the c64 and a 2400 baud
Hayes comp. modem. This adaptor is basically a 3"x3" board with the
following components: A DB25 female connector, an edge connector for
the c64 user port, a chip, a switch that allows me to select between
1670 emulation and Hayes, and a ON/Off switch. The bottom side of
the circuit is coated with a blue stuff (so that no one can find out
the circuitry of this gadget) and the label on the chip has been masked
by a black marker pen. If I find a safe way to remove the marker ink
in the future, I would gladly tell anyone who wants to know. For the
coating , that's another story though.....
I have used the above configuration with two communication software:
CCGMS 6.0 and C64KERMIT. With CCGMS, it works beautifully all the way
up to 2400 baud !!! Though I have not tried up/down load at that
rate. With KERMIT , I only have limited success. KERMIT can allow
work up to 1200 baud. When I tried to use 2400 baud rate, the
only thing I got on the monitor after connecting with the school
mainframe was a series of control characters - i.e. meaningless stuff !
Some time ago on this group, someone posted something about this, I
believe. Can those knowledgeable people shed some light on me please ?
It is nice to be able to connect with all the local BBS at 2400 baud
rate and do some up/downloading. However, my true need is to be able
to use my system and KERMIT to connect with the mainframe to do some
graduate research work while at home. Please help !!!!
PS -> I did not notice any difference between the Hayes mode and the
1670 emulation mode on the adaptor while I was using CCGMS.
Perhaps 1670 is a Hayes comp. device anyway, so there is no
noticeable difference ! But then why does the manufacturer put
this switch in ? I wonder...
Patrick Wong (the novice)
pcw@squid.tn.cornell.edujgreco@csd4.milw.wisc.edu (Joe Greco) (05/13/89)
In comp.sys.cbm article <7932@batcomputer.tn.cornell.edu>, pwong@batcomputer.tn.cornell.edu (Patrick Wong) wrote: ]the circuitry of this gadget) and the label on the chip has been masked ]by a black marker pen. If I find a safe way to remove the marker ink ]in the future, I would gladly tell anyone who wants to know. For the ]coating , that's another story though..... Anybody wanting to design a *cheap* RS232 interface should be using the MAX232 chip, which is no big secret. I believe Steve Ciarcia outlined it's use a few years ago. It generates the needed voltages from a single +5v supply, and should be a snap to use. I haven't actually tried one, since they must be ordered mail order, but I would expect the price to be a fair amount less than a 1488/1489 and support circuitry. -- jgreco@csd4.milw.wisc.edu Joe Greco at FidoNet 1:154/200 USnail: 9905 W Montana Ave PunterNet Node 30 or 31 West Allis, WI 53227-3329 "These aren't anybody's opinions." Voice: 414/321-6184 Data: 414/321-9287 (Happy Hacker's BBS)
brownd@thor.acc.stolaf.edu (David H. Brown) (05/14/89)
In article <7932@batcomputer.tn.cornell.edu> pwong@batcomputer.tn.cornell.edu (Patrick Wong) writes: >the circuit is coated with a blue stuff (so that no one can find out >the circuitry of this gadget) and the label on the chip has been masked >by a black marker pen. If I find a safe way to remove the marker ink [...] If you mean by 'label' the printing directly on the black plastic chip case, I've had some success with a Q-Tip dabbed in denatured alcohol. Yes, you need to be careful-- normal coatings on PC boards wouldn't like an alcohol bath (that's why I use a Q-Tip)-- but it should work. If you mean a printed paper label, I don't know what to tell you. Also, you might want to wait a day or two to give anybody a chance to tell me that this is a dumb idea-- I'm not a tech. or anything like that :-) St. Olaf College has very little to | M M | M M M | M M | M M M | M M | do with the things I talk about! | M M | M M M | M M | M M M | M M | | M M | M M M | M M | M M M | M M | Dave Brown: brownd@thor.acc.stolaf.edu | | | | | | | | | | | | | | | | | | "I _like_ programming the DX-7!" |_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|
elg@killer.Dallas.TX.US (Eric Green) (05/14/89)
in article <2502@csd4.milw.wisc.edu>, jgreco@csd4.milw.wisc.edu (Joe Greco) says: > Anybody wanting to design a *cheap* RS232 interface should be using > the MAX232 chip, which is no big secret. I believe Steve Ciarcia > outlined it's use a few years ago. It generates the needed voltages > from a single +5v supply, and should be a snap to use. The company that my brother works for, SolaCom/CSI, makes modems amongst other things (specialty modems for RF communications, but, still, modems). They're using the MAX232 chip for the design they're currently working on, which consists of an entire remote telemetry unit stuffed into a 6-inch-square space. If they didn't have those space limitations, they'd be using the old-fashioned 1488/1489 pair. Reason? In quantity 100, they can get the 1488/1489 for around 50c apiece. One 1488 and one 1489 are necessary. The MAX232 chip, on the other hand, is close to $2 apiece in that low of a quantity (and, mail order, the cheapest I've seen them is around $3-$4). Mail order, I can get 1488s and 1489s for 65c apiece, and the circuitry to feed them +/-10v (or nearbouts) consists of a couple of diodes and a couple of capacitors, for a total cost of maybe 50c. Note that you need two MAX chips for a complete RS232 interface, so you have a cost of $1.50 vs. a cost of $5. That's at least a $10 difference in retail price (and probably closer to $15). You won't sell a interface based around the MAX chip for $28, that's fer sure.... Moral of the story: "New and improved" doesn't necessarily mean "cost-effective". The MAX chip is cost-effective in the absense of a rectifiable 9vAC power source... power supplies cost money. But on the C-64, where you can readily obtain the voltages necessary, it just don't make sense. -- | // Eric Lee Green P.O. Box 92191, Lafayette, LA 70509 | | // ..!{ames,decwrl,mit-eddie,osu-cis}!killer!elg (318)989-9849 | | // Join the Church of HAL, and worship at the altar of all computers | |\X/ with three-letter names (e.g. IBM and DEC). White lab coats optional.|