Re: Wireless - switchless kernal mod

On Thu, Mar 29, 2018 at 12:26 PM, smf <smf@null.net> wrote:
> I wouldn't use a pilot tone, I'd use a technique similar to
> https://en.wikipedia.org/wiki/1-Wire#Communication_protocol
>
> Pick three lengths
>
> a. start receiving (start receiving if it's idle, or restart receiving if
> not)
>
> b. shift in a 0 bit (don't do this if idle)
>
> c. shift in a 1 bit (don't do this if idle)
>
> Include an address, to allow the same mechanism to be used for other things
> (like a sid switcher).
>
> And a checksum to protect against false positives or receive errors.
>
> Generate the pulses using loops that are located at addresses with that
> address bit set or clear. The lower the address line you use, the more
> useful it will be. SID would require a4 or lower, 6526 (although I can't
> think of what you'd use it for) would be a3. You may need to run time
> generate code for sending the entire packet.
>

The difference between that 1-wire protocol and my case is that in
that protocol at least the master is noise immune. This is not
possible in my case, whatever address line I choose there will always
be previously unknown 1/0 toggles because of normal use of the
computer.

I agree with the loops modulating the address the way you described.
When I created the prototype pcb I devised that address line to be the
A13 signal (not an actual address line but a chip select line
actually) coming to the 16K eprom as the highest address bit. I
thought of putting the sender code below $C000 so that running code
can choose between reading basic or kernal to toggle the address line
to 0 or 1. Along with A13 line /OE signal is also read so only actual
accesses could be sampled.

Actually it's a good idea to calculate the duration of the line being
held low or high but in my case it's not possible to continously drive
this line high or low. The first thing coming to my mind is using the
sum / average of A13 line for constant time periods and adjust the
start and length of that period until the pattern on the sending side
matches the receiver.

It's hard to describe by writing :)