19 May
2005
19 May
'05
5:53 p.m.
Surely there's one encoder and IR transmitter for
the
entire keyboard (there may be several IR LEDs, but
normally they're wired in series and send the same
information). In which case if _any_ keys work, then
it's very unlikely the problem is with the IR transmitter.
Not true. IR formats where the energy density per bit type
differs can fail on specific codes due to the IR LED supply
capacitor failing. E.g. in the Sony SIRC protocol a 1 bit is
transmitted as 1.2ms of carrier and .6ms gap whereas a 0 bit
is .6ms of carrier and .6ms gap. In this case any command that
has a sequence of two or more 1s may fail where a code with
only single 1s way work.
Not very likely I'll admit but it can happen. The easy way to
diagnose this is if it works with brand new cells but cells a
couple of weeks old don't work well.
Lee.
.
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20 May
20 May
12:14 a.m.
Lee:
Not very likely I'll admit but it can happen. The
easy way to
diagnose this is if it works with brand new cells but cells a
couple of weeks old don't work well.
Interesting....can't be a battery issue in this case though since I used
brand new batteries with both keyboards I've got. The other one doesn't
work at all!
cheers
--
adrian/witchy
Binary Dinosaurs creator/curator
www.binarydinosaurs.co.uk - the UKs biggest home computer collection?
4:56 p.m.
Surely there's one encoder and IR transmitter
for the
entire keyboard (there may be several IR LEDs, but
normally they're wired in series and send the same
information). In which case if _any_ keys work, then
it's very unlikely the problem is with the IR transmitter.
Not true. IR formats where the energy density per bit type
differs can fail on specific codes due to the IR LED supply
capacitor failing. E.g. in the Sony SIRC protocol a 1 bit is transmitted as 1.2ms of carrier and .6ms gap whereas a
0 bit
is .6ms of carrier and .6ms gap. In this case any command that
has a sequence of two or more 1s may fail where a code with
only single 1s way work.
Not very likely I'll admit but it can happen. The easy way to
diagnose this is if it works with brand new cells but cells a
couple of weeks old don't work well.
Even then it may not work, if the inductance of the supply leads is
significant. Personally, I'd check/replace any suspect capacitors early on.
If you have a 'socpe or logic probe, see if you can find the drive signal
to the IR transmitter (often the LEDs are driven by a discrete transsitor,
in which case look at the its collector, for example). See if you get any
signal at all from the non-working keys. If you don't then I would really
suspect the membrane.
It's a pity you don't have a matrix layout for this keyboard. If entire
rows or columns are missing, it could be an electronic fault -- a bad
port pin on the microcontroller, or something.
-tony
7156
days inactive
7156
days old
2 comments
3 participants
participants (3)
-
ard＠p850ug1.demon.co.uk -
leeedavison＠yahoo.co.uk -
witchy＠binarydinosaurs.co.uk