My video about the RS-232 ROM (User-Port) Bug. Help for optimizations requested Hello friwnds,
i did my research in transmitting a binary file to the Plus/4 from a Raspberry Pi over the User-Port using the RS-232 protokoll. Of course i ran into the ROM Bug, but finally after a few weeks of headscratching I did it and learned a lot during this journey. I could not reach the 19200 baud, since i am using Basic, so if somebody has experience to lead me the way how to write a stable the reciever program in assebly, i would apreciate it. I am also going to try the parallel protokoll, but i need some advice prior, because i don't want to fry the userport or the Plus/4. Anyway here is the video:
The Famous RS-232 Bug In this episode i demonstrate binary data transfer with Python from a Raspberry Pi to the Commodore Plus/4 over Userport. We will transfer a picture of a Tie-fighter.
Re: My video about the RS-232 ROM (User-Port) Bug. Help for optimizations requested As I wrote on Facebook, it should be enough to connect the RTS pin from the RasPi to the CTS pin on the +4, then just remove all the delays in the sending program, the transfer should proceed as fast as possible.
There's no way to fry the serial port anyway, it's much easier to fry the pins on the RasPi!
Re: My video about the RS-232 ROM (User-Port) Bug. Help for optimizations requested Reading through the conversations I am a little confused now.
So there was a 6551 HW bug, but it was managed by the Commodore team to put CTSsignal (input of 6551) to a fix ground state. In fact it is well stated on the drawing, though the original documentation from Bil Herd show a timing for that CTS signal too.
On the other hand it is told now the Kernal routine had a failure.
Previously a US scener told, that even the Commodore modems could be used on Plus/4 if one of the signals (if I remember well, the CTS) is covered with a tape, otherwise they will fail to work.
Question: if the 6551 HW bug was rectified by a HW solution on the CTS signal how it may cause a problem with the Commodore modems? Or it is also just an urban legend, that the Commmodore modems does not work (as it is) with Plus/4?
Re: My video about the RS-232 ROM (User-Port) Bug. Help for optimizations requested I think Commodore's fix for /CTS is evident in the original +4 schematics:
You can clearly see that pin K is aligned with the /CTS pin of the ACIA and it's likely that they were connected with a straight line like most other pins. Then they must have noticed the issue and redirected the signal to pin 1 of the parallel port.
Anyway pin K is the same pin where /CTS is expected on the VIC20 and C64 userports, as you can see from the VIC-1011A schematics so I would expect the Commodore modems to be compatible with the +4 without any modifications.
Maintaining compatibility with the old VIC20/C64 peripherals that used the serial port signals is also the easiest explanation for why the parallel port pins are scattered around the userport as they are, since the serial port signals could not be moved.
Re: My video about the RS-232 ROM (User-Port) Bug. Help for optimizations requested @SukkoPera I connected the RTS Pin from the Raspi (you have to configure it) and CTS Pin K (Plus/4, Kernel), it unfortunatly it does not work. Either the configuration did not work or theere must be some further configuratiuon on Plus/4 side. I will look more into into it, after i will try out assembly first.
Re: My video about the RS-232 ROM (User-Port) Bug. Help for optimizations requested You might have to do something on the Python side. For instance, if you are using pySerial, it does not use flow control by default.
My video about the RS-232 ROM (User-Port) Bug. Help for optimizations requested
