[Coco] Plugging more stuff in to the RS-232 Pak

[K. Pruitt]

----- Original Message ----- 
From: "RETRO Innovations" <go4retro at go4retro.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Friday, December 25, 2015 10:09 AM
Subject: Re: [Coco] Plugging more stuff in to the RS-232 Pak


> On 12/25/2015 10:21 AM, Dave Philipsen wrote:
>> I would say it's within the realm of possibility.  I suppose you could 
>> somehow wire an LED to a handshake line and do it.  I once wrote some 
>> code to do exactly what you talking about.  It wasn't on a CoCo but I 
>> bit-banged an output bit on a 68HC11-based device to create the signal 
>> for an IR LED which controlled a NTSC video printer.
>>
>> Dave
>>
>>
>> On 12/25/2015 8:06 AM, K. Pruitt wrote:
>>> Is it possible to power an IR LED via the RS-232 pak and successfully 
>>> send a set pattern of signals to an IR-controlled device?
>>>
>>> In other words, can I use my RS-232 pak to turn my CoCo in to a TV 
>>> Remote? I have no idea at what "baud rate" those signals are sent out. 
>>> Can the CoCo match the speed? I'm guessing yes.
>>>
>>> Certainly someone has tried this already, if it isn't just out and out 
>>> stupid. It sounds pretty simple. A resistor or two and an IR LED?  I 
>>> have a bazillion remotes around here I can pull an IR LED from. Am I 
>>> going to blow up my CoCo! Hehe.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
> It is, but you should approach it a bit differently than I think you're 
> considering.
>
> Most IR receivers won't accept RS232 signals, so you'll not have much luck 
> with putting the IR LED on the TXD pin.
>
> What will work better is putting the IR LED on the RTS pin.
>
> You can then bit bang any signal protocol of interest, as you have direct 
> control of the LED
>
> poke &HFF6A,4: REM IR LED ON
> poke &HFF6A,0: REM IR LED OFF
>
> On the DE-9, I'd not wire the LED directly to the RTS pin, as LEDs don't 
> have great reverse breakdown current capacity, and RTS swings between +12V 
> and -12V.  I *think* a register 1n4001 in series would work, so, I'd put 
> the diode in first, put the led onto it, and then a resistor (assuming the 
> LED has a forward breakdown voltage of 1.7V, and uses 20mA, use 
> (12-.7-1.7)/.002 = ~5K resistor) and then ground.  Since RS232 signals are 
> reversed, and I have not played with RTS for a bit on a 6551, you might 
> have to use 4 to turn the LED on and 0 to turn it off.
>
> Of course, then you have to write some ML to bit bang the pin to create 
> your protocol.  Have fun!
>
> Jim
>
> -- 
> RETRO Innovations, Contemporary Gear for Classic Systems
> www.go4retro.com
> store.go4retro.com
>
>
> -- 


Very cool, Jim. Thanks.

I know how to bit-bang the heck out of the command register of the RS-232 
pak.

I think Roger Taylor took this idea to it's logical conclusion with his 
Bluetooth RS232 pak (I came across the manual online this morning). But an 
infrared transmitter/receiver would be cool and seemingly cheap and easy to 
do with no modification to the pak itself. Just a plug-in dongle.