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Getting a SuperPET online

I looked over the manual that you sent me the link to via email. There is this passage:

In the RS-232C port of the SuperPET, the Clear To Send (CTS) line must be at the
right voltage level for the transmitter (serial port) to work. The CTS input line is used
to control the transmitter operation. The enable state is with CTS low (TTL +0 volts).
The transmitter is automatically disabled if CTS is high (TTL +5 volts). If the CTS line is
not provided from the DCE, the correct level is achieved by connecting the Request To
Send (RTS) directly to CTS; thereby, the signal going out to pin 4 goes directly back into
pin 5 indicating that it is "clear to send".

Similarly, most software that runs on the SuperPET would expect to receive the
signals Data Set Ready (DSR) and Data Carrier Detect (DCD) (this is illustrated later on
in a programming example). Again, if there are no lines coming from the DCE cable for
these two signals, the correct voltage is achieved by connecting DSR and DCD (pins 6
and 8) directly to Data Terminal Ready (DTR, pin 20). When the SuperPET indicates
DTR on pin 20, this signal feeds pins 6 and 8 of the serial port, thus returning DSR and
DCD respectively.

I suppose you could try wiring RTS to CTS and DSR to DCD and DTR. That would be a terminal software requirement though. Technically, you only need ground, Tx, and Rx, and that's it for the serial port to work. I would really recommend a tester. That would tell us in 10 seconds where the issue is.

edit: it *is* possible that the CTS is tied to a hardware switch on that particular board. If CTS is high, it might actually shut off the transmit output. If we a had schematic for this board it would be easy enough to know. Typically, this is software checked. CTS & DSR are both low by default with the WiModem232. Again, a tester would instantly show this!
 
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JimDrew said:
Howdy! So, which version of the WiModem232 do you have (V1, V2, or PRO)? I don't see any pictures of it in this thread.

Since you have verified that the WiModem232 works with something else, and the SuperPET works with a real modem (which required changes to the DCD in order to see anything), then I would say your cable is "probably" correct. Keep in mind that the WiModem232 emulates the Hayes protocol and interface specification exactly. You will need to have ALL of the lines passed through using a MODEM cable, not a NULL-MODEM cable (as you found out). Just make sure you are not using a DB25->DB25 or DB25-DB9 cable that is missing some lines. I am not sure what the SuperPET requires, but since the real modem works I would expect the cable to be correct.
The WiModem232 supports +/- 15v (+/-25v peak) standard RS232 signal levels. Lines that "float" or have no current load could read a variety of voltages, so you really can't go by voltages for operation. If you have a DB25->DB25 RS-232 tester (little box that goes between the computer and the modem) that will tell you everything about what is going on. My guess is that the computer doesn't like some state that the WiModem232 is in by default, which I find a bit odd because it is the defacto standard. I have never had anyone so far (out of thousands of these in use) not be able to connect to any type of computer system. Here is the magic device I use to look at the RS232 levels:


You can use any of the various devices. This one is handy because you can turn on/off each of the lines. When you are sending data to the WiModem232 the LED blinks with each transmission of bits. Same for receiving. This takes the mystery of what is going on.

Does your WiModem232 have a display? If so, it will show info when you press the RETURN key after entering a command. It will also show you the current baud rate. By default, it is set for 300 baud. Make sure the terminal really matches this baud rate. If you enter data, like ATI and press RETURN you should see "ATI" on the WiModem232's display. If you don't see that then there is no communication TO the WiModem232, which might be caused by the terminal software not thinking that something is connected (like your AT&C0 discovery with the real modem). Let me know what type of WiModem232 you have, and if it has a display.

I will look into the SuperPET. It sounds like it uses the old school 1488/1489 RS232 transmitter/receiver pair like the Amiga. I will have a look at the schematic of the SuperPET.

Have you tried another terminal program?
Click to expand...

Hi Jim,

Thanks for commenting on this thread. I have the V1.1 WiModem232 without the OLED display (just the single LED).

I have checked the 25pin-to-25pin serial cable with a multimeter, and it is indeed a straight-through cable (not null modem).

I'll try to pick up one of those RS-232 break out boxes you mention, as they seem pretty cheap. The model you linked to isn't available on the Canadian Amazon website, though.

I have indeed checked that the SuperPET serial port is in 300 baud mode.

I haven't tried any other terminal software than the terminal software build into the SuperPET's ROM. I will have to try some other software, but that will involve a bit of a learning curve to see how to mount disk images in the 6809 mode of the SuperPET.
 
JimDrew said:
edit: it *is* possible that the CTS is tied to a hardware switch on that particular board. If CTS is high, it might actually shut off the transmit output. If we a had schematic for this board it would be easy enough to know. Typically, this is software checked. CTS & DSR are both low by default with the WiModem232. Again, a tester would instantly show this!
Click to expand...

I believe this is the schematic for the "combined board" version of the SuperPET that I have:

I found it here:
 
The Amiga 1200 uses the same RS232 buffers as the SuperPET. Not the same ACIA.

As a result, I suspect your problems are related to the RS232 handshake signals.

I remember reading that the SuperPET requires the CTS (Clear To Send) signal to be active before the ACIA will transmit anything, but that the WiModem232 may only support half of the RS232 control lines (depending upon which version of the WiModem232 you have).

As a result, a "standard" cable may not do the job, and a bespoke cable may be required. This is why I suggested making up your own 'breakout' cable.

1. Get the SuperPET to work in "loop back" mode first.

2. Get the TX and RX lines correct between the SuperPET and the WiModem232.

3. Work on any hardware handshake lines required by the WiModem232.

4. Work on any modem configuration commands required by the WiModem232.

To aid this process, some LEDs and 270 Ohm series resistors could be useful as a line monitor.

Dave
 
Well, I made a post and went to check for a response and I don't see the post now...weird!

I looked at the schematic and the circuitry does use CTS to toggle the state of the transmitter buffer (enabled/disabled). When CTS is high the transmitter buffer is disabled, which means the WiModem232 would never get any commands. That line should be negative (0 to -15V). You could check that. Typically, this line is always low unless the computer needs to stop the flow of data from the modem. I don't see DTR/DSR causing an issue with transmit or receive. Without a display it's difficult to know what is going on as far as the WiModem232 receiving data, but you could try sending a command to change the LED brightness. Get that tester! :)
 
 
That is the answer regarding the WiModem232, it is the CTS signal in both cases.

The CTS signal needs to be active for the SuperPET to transmit anything itself and the WiModem232 also requires the CTS signal to be active.

I did suggest the use of simple LEDs and resistors above to make an RS232 monitor.

Dave
 
The WiModem232 is a commercial product. I don't release schematics to any of my products. The pinout is the industry standard for RS232.

A schematic is not going to tell you anything that I can't, since I designed this product. :) I can tell you that the WiModem232 holds the CTS line low (which would enable the Tx circuitry of the serial port board) unless there is a reason to bring it high (modem buffer is full, which is only the case really at 230,400 and higher baud rates where RTS/CTS is actually being done during a high speed transfer). Unless the jumper pads for this modem have been cut (to support DTR/DSR) then there should be no issue. Since it does work with the Amiga, I am thinking that the lines are fine. It could be that DTR is needed, but I don't see that in the serial port board's schematic. As I stated before, a simple test would be to tie RTS and CTS together, as well as DTR and DSR together. DCD really should not matter since that line should really not change states until a connection is made. You can tie these together externally at the DB25 connector that plugs into the PET (disconnected on WiModem232 side at the cable).

It could be that the receiver is not working for some reason, so you don't get data. I think a simple test to see if the transmitter is actually working is by issuing a command to the WiModem232 (at 300 baud, the default baud rate) to change the brightness of the LED. AT*OLED0 <RETURN> would turn the LED off. If that works, the transmitter is working and it's the receiver that is not working.


Ral-Clan said:
Hi Jim....

Turns out there's not any options on the Canadian Amazon site for these rs232 testers. And they're more expensive than on the US site. This one is really the only option, would it do the job:

Click to expand...

Yes, that will work! That shows the state of all of the lines are are concerned with.

You could also look at Aliexpress, Bangood, or one of the other Chinese cheapo supply places.

One thing a tester will do is tell you if there was any difference between how the lines are in the default state with your real modem vs. the WiModem232.
 
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Jim,

>>> The WiModem232 is a commercial product. I don't release schematics to any of my products.

That is fine. I didn't know whether the schematic had been released or not.

>>> The pinout is the industry standard for RS232.

I used to make a living from fixing communication issues at work - it is amazing how many ways people can screw up communications links :)...

I had one 'customer' who believed the salesman for an RS232 touch screen product when he said it was "plug and play". What my customer didn't say to the salesman was that he was plugging the touch screen product into a PDP-11 NOT a PC. He needed some software in the PDP-11 (which I had originally quoted for) but my customer didn't believe he needed. Go figure! Of course, once I explained to the salesman that his unit was going to be used with a PDP-11 and not a PC, he just said that my customer needed software and he needed what I had quoted him for! My price just went up :)!

The WiModem232 appears to be an unmodified V1.1 unit - so the PCB RTS/CTS links are the default.

We have got the SuperPET working fine by joining pins 4 and 5 at the SuperPET. See posts #7 (SuperPET documentation) and #13 (prototype SuperPET loopback connector with 2-3, 4-5, and 6-8-20 - as per the SuperPET documentation).

We also appear to have got the TX and RX lines the right way around.

So, your thought is that the WiModem232 should work by linking pins 4 and 5 at the WiModem232?

It is only running at 300 BAUD, so we should be able to get some sort of communication using this wiring arrangement.

Dave
 
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Pins 4 & 5 (RTS/CTS) being joined together just drives CTS low and enables the transmitter full time. The WiModem232 does this by default. This can be confirmed with a tester. But hey, I have seen stranger things so it would not hurt to just tied 4 & 5 together manually. You won't damage the WiModem232 by doing this. Really without some type of tester, or OLED screen on the WiModem232, there is not much we can do to determine what is going on. Perhaps @Ral-Clan can try sending the command to turn off the LED. If that works then there is some issue on the PET sending data... we need to figure out which end of the puzzle is broken. :)
 
Agreed.

I suspect, somewhere above, that more than one thing has changed during a single step. This may have fixed one thing and broken another... This is why I like to just change one thing at once - hence a 232 breakout box is invaluable.

Dave
 
I thought this as well.. fix one, breaks another, with the end result appearing to be the same. :)

@Ral-Clan - get that tester!
 
Sorry about the pause in responses....I can focus on this project again. Turns out the RS-232 tester I linked to on Amazon.ca isn't available anymore.
Would either of these be good:

www.ebay.ca

DB25 Male/Female RS232 Serial 7-LED Multi-Line Status Mini Tester, TS-R07 | eBay

Find many great new & used options and get the best deals for DB25 Male/Female RS232 Serial 7-LED Multi-Line Status Mini Tester, TS-R07 at the best online prices at eBay! Free shipping for many products!
www.ebay.ca

or

www.ebay.ca

RS-232 Check Tester - VTG computer jack | eBay

Find many great new & used options and get the best deals for RS-232 Check Tester - VTG computer jack at the best online prices at eBay! Free shipping for many products!
www.ebay.ca

The second one has more lines displayed....but the shipping to me is $27CAD!!
 
The one you ordered will be fine. Those LEDs are bi-colorl. So, they will light up either green for a LOW signal or red for a HIGH signal. The versions that have more LEDs are just separate green and red instead of having bi-color.
 
Plug the tester into the SuperPET and see which LEDs illuminate and what colour.

Then do the same for the WiModem232.

Post the results (or post the photographs).

Dave
 
Ok...got the RS232 tester today.

On the Wimodem232 (which is in a TicTac container):

20240910_205112.jpg

And plugged into the straight-through serial cable coming out of the SuperPet:

20240910_205317.jpg
 
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