Posted By
gc841
on 2013-02-06
10:12:22
|  Modem and rs232
Hi,
I'm wanting to connect a non-Commodore modem to my plus/4 user port. The modem has a standard DB25 connection, so I need an adapter or cable to join the two. I haven't been able to find something suitable.
I've heard that C64 rs232 adapters may not fit the plus/4 user port or if they do that they may not be quick enough to go up to 19.2k. In the Hardware section, there is a "parallel port cable" (for plus/4 to pc). It seems to have the right connections, is this what I need? If so does anyone know where I could get hold of one?
thanks.
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Posted By
gerliczer
on 2013-02-06
10:47:40
| Re: Modem and rs232
Hi gc841,
The cable you are talking about is for direct transfer between a PC and a plus/4 so clearly it is not what you want. I'm not aware of any kind of cable for connecting standard modems to plus/4. Those modems require +/-12V signalling but our computer can provide only +5/0V signals therefore some sort of interface is needed. Some hardware gurus may provide you with a solution. Meanwhile, I'd compare the pin-outs of the user ports on plussy and the 64 to see if the interfaces for the 64 still could be operated somehow. If I'm not mistaken, those only do signal level matching, and the transfer is slow only because it is not hardware but software driven.
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Posted By
Hans
on 2013-02-06
11:06:16
| Re: Modem and rs232
Hi,
As gerliczer said, the cable as shown in the hardware gallery is for a direct link to a PC parallel port. I presume that this piece has been homemade. To the best of my knowledge, there are no commercial offers for this kind of cables.
Since the Plus/4 does provide at the userport only TTL (5 V), you would require a level-converter to cope with the 12 V modem voltage.
The Plus/4 has an UART chip (6651 at position U3), enabling the Plussy to up to 19200 Baud.
So you'd need a cable and a level converter, besides of probably a Plus/4 PRG for communication with the modem.
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Posted By
MMS
on 2013-02-06
13:13:00
 | Re: Modem and rs232
you need a MAX232 IC and build a small circuit on that. On ebay you could find complete,very compact ones with RS232 connector. The other side the 3 signals Can be directly connected to the the proper data lines on user port, but you need rare and expensive user connector. Later may give more details on the pin layout, but i am not a hw guy ( nor a sw, haha!). Btw any team around to finish my user port mouse project? I have all the hardwares i provide free (max232 circuits, user port connectors, rs232 mouses, cables),but just moving to a new flat, and out of free time and energy, and all plussy stuff is boxed till ~june. Resident Driver to be written too
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Posted By
gc841
on 2013-02-06
17:28:51
| Re: Modem and rs232
Thank you for the quick replies and info.
I'll look again at the C64 rs232 interfaces. Some of the early ones didn't implement higher baud rates, but maybe later ones did. I'm not familiar with the MAX232 IC but I'll check it out, although if the connector is expensive I would not go down that route. I already have a working 1670 modem, I was just wanting to see my plus/4 running to it's full potential!
I hope that someone will come forward to take on MMS's user port mouse project, it would be great to see it completed.
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Posted By
gerliczer
on 2013-02-07
02:44:01
| Re: Modem and rs232
Hi gc841,
I took a peek at the pin-outs of the two user ports. Mechanically they are the same, but electrically they look very different to me. If you want to build something new the procurement of the proper connector is a bit problematic AFAIK but maybe it can be purchased from Individual Computers. I seem to remember that they announced years ago the capability to manufacturer such connectors.
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Posted By
gc841
on 2013-02-07
04:53:52
| Re: Modem and rs232
Thanks for checking the pin-outs, gerliczer.
There is an rs232 interface called the 'Omnitronix Deluxe', according to the manual (rev. 3) it is compatible with plus/4. However, the baud rates from 3800 upwards may not be implemented. As you explained, and as the manual indicates there are differences between rs232 c64 and plus/4 operation, so it's unlikely that any interfaces around before the plus/4 appeared would work.
Other interfaces, such as the Aprotek Universal, or the VIC1011a (for Vic20?) don't mention any plus/4 compatibility. I'll see if there are any others out there.
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Posted By
MMS
on 2013-02-07
19:12:41
| Re: Modem and rs232
max232: those are cheap stuff: i bought them below 4€, free postage from China.
User port connector: kinda expensive from Uk, ~3€/piece.
You need a db25->db9 converter. Usually if you buy an rs232->ubs converter for ~4€, you get one free in the package. I think i have one free, i may give to your project.
The rs232 mouse idea is not mine, but from BGSSZ, I linked his page in a previous mouse topic. He had no drawings, circuit diagram or parts, so i started from beginning. He had an unoptimised sw to regularly read position into register. I planned to optimise it and to support paralelly SID mouse too. Sprite emu was not in focus, planned to be used from BASIC with Gshape mouse cursor, in my planned adventure.
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Posted By
Litwr
on 2013-02-08
01:08:33
| Re: Modem and rs232
GEOS needs a mouse!
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Posted By
gc841
on 2013-02-08
04:51:32
| Re: Modem and rs232
MMS, thanks for the offer of a DB25-DB9, but I found a cable in the box with my modem. As you probably guessed, I'm more of a 'plug-n-play' type than 'build-it-yourself' so if I can find a completed product, I'll go for it. If they prove to be too rare or expensive, I'll go with your suggestion.
I also looked at the individual computers website, but didn't find the suitable connector. I'll contact them. This is all appreciated, I have enough info to go forward now.
On the software side of rs232, I read recently that the plus/4 rs232 was not tested by Commodore, and there are one or more bugs.
1) According to SVS's memory map, the lines of code at $EAA7 and $EAA9 have to be swapped to allow null characters to be received.
2) In the Aug-87 issue of 'Your Commodore' (available at archive dot org), an article by RC Hemes mentions a bug (bottom of page 83). It describes how the plus/4 crashes when sending the first resume character for XON. The solution is to insert a PLA command at $EB1E. I've looked at the code but don't really understand much of this.
They sound like two different bugs to me? Are there any other known bugs for rs232?
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Posted By
gc841
on 2013-02-10
03:11:26
| Re: Modem and rs232
Spektro,
I had a look at that adapter, but noticed that there are no pins for CTS/RTS. You would pay more for one of these:
http://www.ebay.co.uk/itm/HQ-RS232-to-TTL-5-0V-converter-MAX232-/270758733829?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item3f0a7a6805
then you have CTS/RTS. It would be useful to know what hardware flow control gives you. As you can see, the IC on this board is socketed, so easily replaced.
The old commercial adapters seem to be pretty rare, so I ordered a user port connector yesterday. A UK seller has put some up on ebay (search "Commodore User Port Connector") if anyone is interested. Presumably the connecting leads are standard, easily available.
I'll wait for confirmation from someone that these are suitable, then will get one or the other depending on replies.
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Posted By
MMS
on 2013-02-10
19:23:44
| Re: Modem and rs232
GEOS Mouse: yes, it was in focus, so the driver of 1351 downloaded, also a kind of source code too... I suppose it should not be too complex thingy to change few register values (had no time to investigate), theoretically the c64 GEOS driver of 1351 already capable to support mouse connected to Plus/4 SID Card, if ported to same registers. Though this version is much more expensive than a 10€ Max232 circuit + cheap rs232 mouse, i do not want concurring standards and wanted to support both in the resident driver. I planned to give the adventure free for those folks buying my cart+mouse, or the opposite way 
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Posted By
Spektro
on 2013-02-11
01:16:28
 | Re: Modem and rs232
gc841,
Ah, all the signals are needed. I tried to figure out how to connect the adapter, which you pointed out, to the plus4's user port, but since I'm not a HW person this most likely will go horribly wrong:
Adapter | User port pin
VCC | B?
RxD | M (Transmitted Data)
TxD | B (Received Data)
GND | N (Signal Ground)
CTS | K (Clear to Send)
RTS | D (Request to Send)
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Posted By
gc841
on 2013-02-13
04:45:41
| Re: Modem and rs232
Spektro,
Thanks for the connection info, I'll take a closer look at that when my adapter arrives (ordered yesterday).
It's worth noting that some of the DB9 lines don't appear to be implemented in these modern 232Max boards:
DSR/DTR data set/terminal ready
RI Ring Indicator
CD Carrier Detect
I'm not sure what device(s) you were planning to connect to, but modems can use all three of these, some printers may use DTR/DSR, so workarounds may be required.
MMS, As long as you can connect the mouse to a stock plus/4, I'd want to buy one.
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Posted By
Spektro
on 2013-02-14
09:13:27
| Re: Modem and rs232
I'd be very interested in hearing if you manage to get the adapter working. If you're successful, I'll order one, too
I thought I could try connecting a modem but it turned out that I don't have an external modem anymore  I was pretty sure I had one but I only found an internal modem.
Well, I still have a null modem cable and a mouse to test.
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Posted By
MMS
on 2013-02-14
18:47:02
| Re: Modem and rs232
Hi,
I am also damn sure, that I still have an external modem, and it should lay somewhere here Anyone needs it, just let me know. It is a normal PC modem you are talking about, right?
Did I mention, that I started a page on this matter some time ago?
Certainly with a lot of useless text, as usual, sorry... 
http://my.opera.com/MMSZoli/albums/show.dml?id=11886182
Hardly updated after received my
You can find the link to the original BGSZ RS232 project, click to Fejlesztesek to see some photoes about a working one (left bottom part of page)
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Posted By
gc841
on 2013-02-15
05:18:50
| Re: Modem and rs232
I'll let you know how I get on. The user port connector is coming from US so may take a few weeks to arrive, I'm also waiting for the max232 board and a db9 m/m connector. I have an external pc modem (Multitech 19.2k) with a db25 to db9 cable.
Thanks for the link, MMS. It is interesting to see your project coming together.
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Posted By
MMS
on 2013-02-17
15:16:07
| Re: Modem and rs232
my max232 came from hongkong, and it took 4 weeks to arrive with smailmail
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Posted By
Litwr
on 2013-02-19
10:23:24
| Re: Modem and rs232
IMHO the absence of mouse is the greatest disadvantage of +4. I used mouse with my first PC. It was without hdd, had CGA monitor but it was with a mouse.
If I am right SID card gives possibility to use C1351 so if there will be drivers then emulators may provide support for the mouse. The idea of RS232 mouse looks too good for our reality.
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Posted By
DeadTED
on 2013-02-19
19:02:47
| Re: Modem and rs232
Gc841, I have made a plus 4 serial port using the max232 chip and successfully used it to transfer data to my pc via basic, if you can't gets yours to work, happy to make one for you.
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Posted By
gc841
on 2013-03-07
05:49:04
| Re: Modem and rs232
DeadTed, thanks for the offer. I'll see how I get on, I'm just waiting for the user port connector now.
UPDATE:
I now have everything set up, but no response back from AT commands to the modem. So I tested the following:
pc --> modem two way comms work
pc [running minicom] --> usb to serial --> ttl adapter --> plus/4 [running higgyterm] works one way only, plus/4 to pc
So it seems that the ttl adapter to plus/4 is the problem (rxd). I tried using pin b only and pin c only for rxd, but do not have
the means currently to test using pins b+c together. The C64 needs both b+c, but I can't find any specific info for the plus/4 requirements.
Any help would be appreciated, thanks.
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Posted By
DeadTED
on 2013-03-09
20:58:24
| Re: Modem and rs232
Ok I'll tell you what I am going to compile all the information I used to build and test mine and compile it into a write up to post on the site including the basic programs I used to transfer files between the plus 4 and a PC. I also used the sample basic program in the user manual on page 212 to send AT commands to a connected modem. Also if it helps the circuit I built was adapted from a c64 design, all I had to do was change the connections to the userport as thy are different between the c64 and plus/4.
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Posted By
DeadTED
on 2013-03-10
05:06:03
| Re: Modem and rs232
if you are handy with th soldering iron this interface is exactly the same as th one I made and can b easily modified to make work with the plus 4
http://www.ebay.com.au/itm/Interfaccia-seriale-RS232-per-Commodore-64-128-Serial-Interface-Adapter-/261182681206?pt=Vintage_Apple_Macintosh&hash=item3ccfb37076&_uhb=1#ht_500wt_922
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Posted By
gc841
on 2013-03-10
07:03:30
| Re: Modem and rs232
I've now got two way communication and managed to login to my pc from my plus/4. More than 40 columns would be nice, pc was expecting a VT102 so running lynx (browser) & alpine (mail) wasn't great. I'll test modem to plus/4 later. I wrapped some wire around pins b+c as a temporary solution, but also had to disable hardware flow control for it to work. So I still don't know whether connecting both pins was required. Will update when I know.
DeadTed, it would be great if you could make your docs available, thanks The Plus/4 Encyclopedia section would be the right place to add your docs, you would need a login though. If not, I can add them.
The serial interface looks good, but I've already bought a max232IC board, user port connector etc (and I'm not much of a solderer), it may be useful for others though.
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Posted By
DeadTED
on 2013-03-11
11:24:31
| Re: Modem and rs232
OK the rs232 interface I created has now been fully documented, who do I email the PDF doc to to have published? BTW the +4Man alias = DeadTed. I had some difficulties with the site recently and started using DeadTed instead :)
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Posted By
MMS
on 2013-03-11
19:47:43
| Re: Modem and rs232
congrats! I will surely read it as soon as it reaches HW section.
BTW the mouse pretty much simplier as communicates one way only. The only issue is power need of mouse, so i ordered MAX232 boards have possibility to connect external psu too
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Posted By
DeadTED
on 2013-03-11
22:45:05
| Re: Modem and rs232
Yeah the circuit I have document uses the MC1488 and MC1489 chips, it's old fashioned but works great.
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Posted By
gerliczer
on 2013-03-21
13:47:40
| Re: Modem and rs232
I had quickly paged through the new issue (68) of Commodore Free and the Comet64 advertisement caught my eyes. A quick googling yielded these two links: http://www.commodoreserver.com/Products.asp and http://cometplus.net/. The second, although plus/4 compatibility is specifically mentioned, is not a final product yet but maybe it is worth to ask the Comet64 guys about using their modem with plus/4.
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