1050-2-PC cable wiring - is DTR required or can I use RTS?

[VW]

I have been having a horrible time trying to wire up my Raspberry Pi's serial port to work with 8-bit hardware. I bought a serial port add-on board for the Pi and tested it using minicom connecting to an old Cisco router and that worked so I think the port is ok but atariserver and atarixfer don't work at all. I looked deeper and various online diagrams for the 1050-2-PC cable use 5 wires (Tx, Rx, VCC, GND, and another one I have seen labeled as CTS, RTS or DTR).  I just realized that my Pi's serial port only has 4 wires connecting to the Pi's GPIO (Tx,Rx, VCC, GND). I have read that DTR is not possible on the Pi but RTS is.  Can I get by with RTS? My add-on board has a small pin I think I could get to work with another connector. I am using an old (bought 15-20 years ago) 1050-2-PC cable and I don't know whether it uses RTS or DTR. I guess I could rewire it if needed but would prefer to avoid that.  How critical is this difference?

Edited September 18, 2020 by VW
added CTS as a possibility to use

[+kheller2]

Are we using the right terminology here?  1050-2PC is connecting a 1050 Floppy Drive directly to a computer, not a computer to the Atari. I think SIO2PC needs GND, CTS, TX(with diode), RX.  10502PC needs GND, VCC(resistor), TX, RX, DTR.

 

 

[+DrVenkman]

An SIO2PC-USB device needs whatever control signal the software you're using on the PC is set to expect. The device and the Atari itself are agnostic in that regard.

 

That said, I have a device that uses DSR and works great. 

[HiassofT]

1050-2-PC mode needs a command line (usually driven by RTS or DTR) and 5V/VCC/Ready in addition to RxD, TxD and GND connected to the 1050. The 5V/Ready pin is important, if 5V isn't present there the 1050 will play dead.

 

On most older 1050-2-PC interfaces connecting to PC serial ports you had to provide the 5V externally as it's not available from the serial port and deriving it from the control lines of the serial port is problematic.

 

On the RPi it's easiest to just use 3.3V<->5V level shifters to connect to the 1050 or Atari, the cheap 4-way bidirectional FET level shifters work fine - see README.RPi in atarisio (also note that you need to add the overlays to get RTS and CTS on the RPi GPIO pins).

 

Your serial port addon board/hat sounds like it may contain a RS232 line driver, converting from 3.3V to the +/-12V RS232 levels. If it doesn't provide RTS and CTS signals by default it may be tricky to rewire it to support these. Also going from 3V on the RPi to 12V on RS232 and then back to 5V in the 1050-2-PC interface adds more points where things could go wrong (eg a slow line driver that's then preventing reliable operations) - better avoid that.

 

If you want an off-the-shelve solution I'd recommend buying the SIO2PC/1050-2-PC USB dual adapter from Lotharek. It works just fine with atariserver/atarixfer (see README.lotharek for details on how to switch it to 1050-2-PC mode).

 

Using an old, serial 1050-2-PC cable with a FTDI based USB-serial adapter works, too, if you externally provide 5V. USB-serial adapters with other chips is hit-and-miss (in general more miss than hit), as they often don't support signalling when the transmission has finished (which is essential in 1050-2-PC mode). SIO2PC mode is more forgiving in that aspect.

 

so long,

 

Hias

[TGB1718]

If you bought yours about 15-20 years ago, it may be one of these by Nick Kenedy,

1050-2-PC and SIO-2-PC, these devices convert the +5VDC to +/-12VDC for the RS232

port on the PC, so be careful if your connecting the RS232 side to your Raspberry Pi.

 

 

[VW]

6 hours ago, HiassofT said:

1050-2-PC mode needs a command line (usually driven by RTS or DTR) and 5V/VCC/Ready in addition to RxD, TxD and GND connected to the 1050. The 5V/Ready pin is important, if 5V isn't present there the 1050 will play dead.

 

On most older 1050-2-PC interfaces connecting to PC serial ports you had to provide the 5V externally as it's not available from the serial port and deriving it from the control lines of the serial port is problematic.

 

On the RPi it's easiest to just use 3.3V<->5V level shifters to connect to the 1050 or Atari, the cheap 4-way bidirectional FET level shifters work fine - see README.RPi in atarisio (also note that you need to add the overlays to get RTS and CTS on the RPi GPIO pins).

 

Your serial port addon board/hat sounds like it may contain a RS232 line driver, converting from 3.3V to the +/-12V RS232 levels. If it doesn't provide RTS and CTS signals by default it may be tricky to rewire it to support these. Also going from 3V on the RPi to 12V on RS232 and then back to 5V in the 1050-2-PC interface adds more points where things could go wrong (eg a slow line driver that's then preventing reliable operations) - better avoid that.

 

If you want an off-the-shelve solution I'd recommend buying the SIO2PC/1050-2-PC USB dual adapter from Lotharek. It works just fine with atariserver/atarixfer (see README.lotharek for details on how to switch it to 1050-2-PC mode).

 

Using an old, serial 1050-2-PC cable with a FTDI based USB-serial adapter works, too, if you externally provide 5V. USB-serial adapters with other chips is hit-and-miss (in general more miss than hit), as they often don't support signalling when the transmission has finished (which is essential in 1050-2-PC mode). SIO2PC mode is more forgiving in that aspect.

 

so long,

 

Hias

The serial port is powered from RPi's 3.3VCC pin and I think shifts from there.  So would I need to connect both RTS and CTS for this to work then? I tried just using the RTS overlay and didn't have any luck. My serial add-on doesn't have pins for RTS/CTS but I could probably solder them as there are spots for them on the board. If I do that, would I use the default atarixfer cable option or is this equivalent to Lotharek's or the APE cable?  It sounds like Lotharek's SIO2PC/1050-2-PC with USB dual cable would solve all my problems and be a lot easier to deal with so I will probably just do that. Thanks everyone for all your replies!

[HiassofT]

atarixfer uses RTS by default (that's the signal used by standard 1050-2-PC cables). APE prosystem uses DTR.

 

You don't need CTS for atarixfer, but you'd need that when using atariserver with a SIO2PC cable.

 

Don't forget to supply 5V to the 1050-2-PC cable though.

 

so long,

 

Hias