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I want to build a RS-232 interface, but I don't know how to. Anyone know how or have any suggestions, and what is the best terminal software I can find?

floopy wrote:I want to build a RS-232 interface, but I don't know how to. Anyone know how or have any suggestions, [...]

If you insist on +/- 12 V for the signal levels (because "TTL level" RS 232 wouldn't do), the schematics of the VIC-1011 VICModem are found here:

ftp://ftp.zimmers.net/pub/cbm/vic20/sch ... 011005.gif

and what is the best terminal software I can find?

Depends on what suits your needs best. >:)

o VICTerm 40

o Mighty Term 8192

o Plus Term

are those which are archived at zimmers, and there has been a lively discussion about RS232 applications in the Programming Section recently.

Plus there is Jim Brain's EZ232, which has some details and schematic here:

http://www.commodoredungeon.com/images/ez232-2.pdf

More details here:

http://jbrain.com/vicug/gallery/ez232?page=1

Works fine on the VIC, I have one in a box somewhere. Dmackey used to make and sell them, he might still have a few:

http://www.n2dvm.com/blog/2016.html

Floopy wrote:I want to build a RS-232 interface, but I don't know how to. Anyone know how or have any suggestions, and what is the best terminal software I can find?

Do you want to build a level shifter so you can use the builtin serial device or a complete replacement interface? The internal interface works but has some limitations

• It's slow, 1200 baud is the top rate that's reliable (and only then from machine code)
• It's inefficient, because it uses bit banging it consumes significant CPU time in the NMI routines
• The hardware flow control is broken (a number of bugs that were eventually fixed in the C64)

For some purposes this is acceptable so all you need is circuitry to shift from TTL to & from +/-12v. This can be done with a single chip (plus a few components) that contains a voltage doubler and inverter such as the MAX232. If you can wait for a couple of weeks you can buy a complete board from China for a little more than a dollar, search eBay for "RS232 to TTL".

If you're more ambitious then building a new RS-232 port using a UART is an option. Hooking up something like a 16550 (as originally used by PCs) is a bit more complex but you can then run at much faster speeds. You do have to write custom software to use it, of course.

I've built and used both solutions, it depends on what your end goal is.

Okay thank you everybody, that's all I wanted to know.
I find this amazing: I ask a question and a day or two later answers come. Sometimes I would spend hours searching for topics.
Thank you everybody for your time and knowledge.

srowe modestly did not mention that they created a wedge that replaces the VIC-20's buggy RS-232 kernal code.

Hardware flow control seems to work with this RS-232 wedge. (At least I can use the RTS line to 'pause' and 'unpause' the modem.)