Re: TI-H: Re: Quick radio link survey
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Re: TI-H: Re: Quick radio link survey
On Fri, 24 Mar 2000, Aaron Peterson wrote:
> I'd like it to be easy to build and easy to attach to the calculator.
At this point the idea is to use a commercial radio module and a
microcontroller connected to the link port. The radio module makes up
most of the cost of the thing, but also provides very solid and fast radio
support, so I think it is worth the price. A home built design is
certainly possable, and would likely work well, but would be much less
reliable.
> Network compatability would be super awesome.
Network support would pretty much require software drivers, as the
calculator obviously does not support multi-link. One driverless option
would be to put a two sets of 4 bit dipswitches on the link, in 'network'
mode the switches would all be off, in direct connect mode the switches
would be set to 'source' and 'destination' addresses. The microcontroller
would always receive all broadcast data, and only send on what was
intended for it, This would allow multiple calculators to operate in
'direct' mode without disturbing other calcs on the network.
> > An option to switch between driverless TI-protocol mode
> > and a software driver mode (for backwards compatibility
> > mostly, to allow existing custom link protocols to work).
> Very important for transfering drivers to friends.
>
> I'd like to be able to build a version that uses link cables instead of
> radio so my less technically inclined friends could use it too.(radio mode
> or link mode in 1 box)
Not quite sure what you mean, the calculator already supports link cables.
> Network is very important.
> Have radio boxes as hubs with cables to calcs.
Connecting multiple calculators to a radio hub would be a bit more
complicated, and while technicly pretty neat, I don't think it would be
very useful at all.
> I am willing to pay $50 plus building it. (if it had the cable network
> option so my friends could use it)
> $70 if I could use the radio for more things than just networking calcs...
> (like voice... or baby monitor)
> These are if it is a 2way link.
$50 is below what I would be willing to make them for. The cheap parts
for one side of a link come to around $70, plus incidental parts (the
microcontroller, A 'homemade' tranceiver module would be cheaper, but
would also require orders of magnitude more design work, and would
probably not be anywhere near as reliable (depending on who makes it of
course, I'm sure there are people out there who can design a double
conversion FM superhet receiver from scratch, but I ain't willing to do
it).
> If there is an option to make a plain 1way link $50 for both the send and
> recieve modual.
> (This would be usefull for teachers to transmit data to students in a
> classroom... it would also eliminate collisions)
Yes, you could do that, but the receiver is actually the more expensive
side, and would probably run about $70 or more complete. Transmitter
would be somewhate less than that.
> Another feature that would be nice... a directional antena option. I don't
> like super long range stuff because it could interefere with others. If
> there were a way to focus the low power guy to be able to go long range in 1
> direction, that would be awesome!
Its much easier to simply limit your broadcast power, but a directional
antenna could probably be built.
The prices I've mentioned are just guesses, and at these levels, anyone
selling them would probably be taking a loss. Decent radios are
expensive.
Data can be transmitted much cheaper, using very simple circuits, but
after adding error correction and retransmissions, the data rate would end
up being pretty low.
I'm still looking into options though, so maybe the cost can still come
down a bit.
DK
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