Jean Tourrilhes wrote:
>
> By the way, any comments about the quality of Ir tranceiver ?
> We had trouble with every Ir transceiver we use in presence of
> fluorescent light and outside. The medium is detected as busy, packet
> are corrupted and all that jazz... Your dongles tend to be slightly
> better (but still so easy to confuse), the absolute worse being the Ir
> transceiver fitted on a popular WinCE device just released by a
> manufacturer that I don't want to name (a bit of sun, and gone).
> With radio stuff (802.11, GSM), most of the cost of the
> hardware in in the saw filter and other active filters, which reject
> frequencies from adjacent bands and keep only the energy present in
> the desired band. Those filters tend to be pretty tight and efficient.
> With Ir, it seem that all manufacturers don't use any
> filtering of the incomming signal (the receiving led is connected
> directly to the digital) and don't really care about this...
Garst wrote:
> Try a bit of exposed colour film, such as that at the end of just
about
> any role you get developed. Scotch tape it over the port. Works
wonders.
The peak wavelength of the IR LED used in IrDA
devices is specified in IrPHY, but the spectral
width is not specified. This is to accommodate
variations in (cheap) IR LED. But as a result,
we cannot use a very narrow band optical filter
to eliminate the noise from sunlight and
artificial lights.
The other source of interference is usually poor
PCB layout near the IR receiver. But this is
electrical and has nothing to do with sunlight
or artificial lights.
The direct IR LED driver usually does not cause
any problem.
Actisys dongles use IR transceivers made by other
companies and we have to be able to receive IR
generated by other IrDA devices. We tried our
best in selecting the optical material used in
the IR window. We also have a very good PCB layout.
As you found out, ours are better than others, but
perhaps still not good enough.
The exposed color negative is kind of an optical
filter. It might help for certain IR LED under
certain background lighting conditions. But I do
not think it works well under other situations.
Lichen Wang
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