[Coco] Where can I find information on using the Cartridge port for I/O ?

[Rick Ulland]

The keyboard connector/Mylar ribbon is a sore spot. If Tandy had only 
sprung for a SIP pin header and some wires...

Have a look at the CD4066 'quad bilateral switch'. It connects anything 
that needs a switch, even analog bidirectional. Dime a switch, but needs 
no support beyond a decouple cap and can be powered by a potato. I 
really like these things as a no-brainer drop in.

-ricku

  PS: Insteon? I have a good bit of abandoned Insteon hardware from the 
old Mr House days. Will have to have a read on (and get some vinegar to 
clean all those battery wells).


On 12/24/20 5:03 PM, Neil Cherry wrote:
> On 12/24/20 4:52 PM, Rick Ulland wrote:
>>
>>
>> On 12/24/20 12:47 PM, Neil Cherry wrote:
>>> I'll start out simple as I'm sure there's a lot I don't know.
>>>
>>> I want to build a cartridge with an interface to a USB keyboard 
>>> using the CH376. What information
>>> is available for using the Cartridge port for I/O with ROM on the 
>>> board. I'll need the board to
>>> be read at startup so that it can add the interrupt chain.
>>>
>>>
>>> CH376
>>> https://www.mpja.com/download/31813MPSch.pdf
>>>
>>
>>
>> Most keyboard mods I am familiar with emulate the physical 
>> connections of the CoCo keyboard, and are plugged into the keyboard 
>> connector. Because...
>>
>> The cartridge port doesn’t give you a lot to work with. It was 
>> designed for one software ROM select (CTS) and one hardware select 
>> (SCS), and includes one return (CART) that ECB/DECB interprets as 
>> ‘run the ROM’. Since there will only ever be one, a disk controller 
>> with onboard ROM can ask to be auto-executed and lean on these three 
>> signals, needs little decoding hardware onboard.
>>
>> The MPI can switch between 4 different 1+1 devices, but you can’t 
>> effectively manage that from the MPI side, and worse, it switches the 
>> CART return to the one & only active device this scheme can handle. 
>> OS9 folks physically ‘strap’ all four slot’s CART lines together so 
>> any slot can trigger an IRQ poll sequence, but that is both 'hardware 
>> hacking' and polling doesn’t exist in DECB anyway - no IRQ for you!
>
> I actually have a better method for interfacing a keyboard to any 
> vintage computer. I found a
> method to use a microcontroller (uC) and a 1: ration of transistors to 
> rows and columns. The
> uC translates the USB keyboard to the vintage computer map. I just 
> wanted to play a bit with
> the CH376 (which can also handle any HID device, such as USB sticks 
> and mice and weird things
> like digital I/O and ADC/DAC boards I have). I also plan to attempt 
> this with my Atari 800xl.
>
> >
> > Sorry to be no help whatsoever.
>
> I learned what it can't do, that's as important as what it can do. I 
> was hoping for a non-
> invasive method, but they're not all designed that way.
>
> The tranistor method require I solder a set of single row socket to 
> where the keyboard
> ribbon attached. This should allow the original keyboard to still 
> operate.
>