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PICList Thread
'IrDA Communications Update'
2000\03\23@182428 by Mark Newland

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Earlier I asked some questions as to IrDA implementation.  Several of
you gave me some pointers and thanks to Scott Dattalo, I was able to
find an implementation of it on the Scenix site. As promised, here is my
update as to how we can all handle IrDA capabilities.

============================================================

HISTORY:
Called and left a message with Microchip concerning IrDA.  Next day no
response so called again.  Finally got hold of someone and told them
what I needed and they told me they would get back to me later.  Still
waiting.

Called Scenix and left a message.  Got called back within an hour.  The
salesperson told me she would forward the 'request for info' to an
applications engineer.  Two hours later was called by Jud (the
applications engineer).  He helped me decide/confirm the best route to
go.

============================================================

CONCLUSION:
Their largest IC wasn't big enough for my application AND for IrDA.  At
the same time, putting the IrDA stack onto a PIC chip may be a bit
overwhelming of a challenge.  Therefore my current plans are to use the
Scenix SX28 for the IrDA stack and then use a simple SPI interface
between that and my PIC16C77.  If I went with the C77 for the whole
thing, would have had to use an external IC anyway for the IR wave
shaping.  The Scenix chip can do all the wave shaping within software
AND does the IrDA stack at the same time.

============================================================

SUMMERY:
I hear alot of people on hear talking bad about Microchip and say they
are going over to Scenix (greater speed, built in emulator, etc.).  I
also hear the devout PIC users that say that Scenix is too limited in
what they offer (program space, A/D, different types of families, etc.)
and stay with the PIC's.  I think this is an great example of the need
to be flexible and diverse.  I for one will use BOTH!!!

2000\03\23@222130 by Dan Michaels

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Mark Newland wrote:
>SUMMERY:
>I hear alot of people on hear talking bad about Microchip and say they
>are going over to Scenix (greater speed, built in emulator, etc.).  I
>also hear the devout PIC users that say that Scenix is too limited in
>what they offer (program space, A/D, different types of families, etc.)
>and stay with the PIC's.  I think this is an great example of the need
>to be flexible and diverse.  I for one will use BOTH!!!
>

Mark,

I am here to concur with you. My last project used both a PIC16C76
and an SX28, exploiting each for its maximum benefit. I used a little
multidrop RS-232 bus, so both can talk to a host PC on the same line.
[If only the dang SX had more RAM].

BTW, in your case, did you possibly try running the SX as a
non-VP, using the hardware interrupts?

best regards,
- Dan Michaels
Oricom Technologies
http://www.sni.net/~oricom
==========================

2000\03\23@230046 by Dan Michaels

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At 07:30 PM 3/23/00 -0800, you wrote:
>Not sure what you mean by running the SX as a non Virtual Perf.???
>

Mark,

The normal Scenix route is to use the timer to generate a periodic
interrupt, within whose ISR you perform all the VP servicing.
You use RETIW to return.

However, by non-VP, I meant programming the chip like any normal
chip, where you have a main code loop and aynchronous external
interrupts, such as RS-232 on an I/O pin. Here you use RETI
to return.

- Dan Michaels

2000\03\24@034250 by Terry

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I recall bout 3 years back seeing an eval board for HP's IrDA modules done
by Parallex. Far as i can tell there was a PIC in there doing all the work
getting data to and from a PC. Was i wrong or is the high speed IrDA's too
much work for a PIC?

Terry


At 08:16 PM 3/23/00 -0700, you wrote:
{Quote hidden}

2000\03\24@110809 by Dan Michaels
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At 04:41 PM 03/24/2000 +0800, you wrote:
>I recall bout 3 years back seeing an eval board for HP's IrDA modules done
>by Parallex. Far as i can tell there was a PIC in there doing all the work
>getting data to and from a PC. Was i wrong or is the high speed IrDA's too
>much work for a PIC?
>
>Terry
>

I would say definitely too much work. I tried to run a 400 Ks/s 12-bit
serial A/D off a 20 Mhz PIC, and the best rate I could ever get was a
little over 300 Ks/s, no matter what I did. Involved 2 successive 8-bit
SPI transfers, plus read/store/indexing/looping/etc.

best regards,
- Dan Michaels
Oricom Technologies
http://www.sni.net/~oricom
==========================

2000\03\24@122415 by Mark Newland

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But with the max speed of an IrDA connection (slow speed mode) being only 115k,
that is about half the speed you were running at Terry.  The problem I see Dan
is when you have to do OTHER things at the same time expecially in a
multi-tasking real-time OS.

Could a PIC do the job?  I still think it could.

Would it take away alot of the resource to do so?  Yes!

Would you have enough resources left to do any REAL project?  Maybe, maybe not!

Would you have to use some external IC's if the IrDA stack was on a PIC.
Absolutely, and you would still have to do alot of programming on the PIC as
well!

Would you need to use any OTHER external IC's if you use the Scenix chip AS the
external IC?  No,  the Scenix IC can handle ALL of the IrDA stack but with
nothing left over on the Scenix to do anything real.

Therefore Dan, a PIC probally was doing alot of the getting data to and from
the PC but there almost had to be some other external IC's handleing at least
part of the IrDA stack.

Dan Michaels wrote:

{Quote hidden}

2000\03\24@123837 by Dan Michaels

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Mark wrote:
>But with the max speed of an IrDA connection (slow speed mode) being only 115k,
>that is about half the speed you were running at Terry.  The problem I see Dan
>is when you have to do OTHER things at the same time expecially in a
>multi-tasking real-time OS.
>
>Could a PIC do the job?  I still think it could.
>
>Would it take away alot of the resource to do so?  Yes!
>
>Would you have enough resources left to do any REAL project?  Maybe, maybe not!
>

In order, not using multi-tasking OS, yes, yes, and barely. The PIC
should easily handle 115K anything, but Terry asked about "high-speed" IrDA,
which is 1+ Mhz. [maybe the 10th generation PIC will do it].
================

>
>Would you need to use any OTHER external IC's if you use the Scenix chip AS the
>external IC?  No,  the Scenix IC can handle ALL of the IrDA stack but with
>nothing left over on the Scenix to do anything real.
>

>From my experience (about 10 months) with the SX, I'd agree with this.
The SX can do *ONE* really fast VP (but then it's pooped out). In fact,
I switched over to a Scenix to clock the 400 Khz A/D chip I mentioned.
Also, was able to implement "equivalent-time sampling" going to 5 Ms/s.

best regards,
- Dan Michaels
Oricom Technologies
http://www.sni.net/~oricom
==========================

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