12v from 850 serial ports?

[Fletch]

I was looking at one of my Atari 850's the other day and it occured to me that it might be possible to use the serial ports to act as programmable on-off switches for small 12v devices.

 

I guess my first question is whether or not the 850 would give off 12v dc from it serial ports? If so, what pins would be needed for power and ground?

 

Alternatively, I guess I could use the joystick ports from an 800 if that would work.

 

If this is possible, i'll try and dig my 850 manual out of the attic and give it a go.

 

Any hints would be awesome.

 

Thanks!

 

Pete

[Cybernoid]

It is possible to get ground and +12V from the 850. Ground is pin 5, and you can use DTR (pin 4) or RTS (pin 7) for +12V if you force them "On".

 

You can force DTR or RTS or both "ON" using the "XIO 34" command:

 

To force DTR:

"XIO 34, #1, 192, 0 "R1:"

 

To force RTS:

" XIO 34, #1, 48, 0, "R1:"

 

 

There are some things to remember: You can use DTR and RTS on port 1, DTS only on ports 2 and 3, and RTS only on port 4, I think:

 

Also, the signal levels for serial are +12V and -12V, so when DTR or RTS are "off", they are driving -12V, so not too useful for a power switch, unless you place a diode or some other voltage limiting circuit out side the 850.

 

Check here for more info:

http://home.comcast.net/~atariguy1/atari/8.../appendix7.html

http://home.comcast.net/~atariguy1/atari/8...ter3.html#limit