<houkime>
what to do with it? Is it critical for n900 software compatibility?
<houkime>
if not one can just upgrade it. If it is, what interface exactly is needed fom sensor to be compatible?
<Joerg-Neo900>
>>Is it critical for n900 software compatibility<< no, it's a Neo900 bonus feature
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<Joerg-Neo900>
implement as you see fit
<Joerg-Neo900>
took a while til we found that sensor
<houkime>
ams has newer similar models.
<Joerg-Neo900>
interface is overkill
<houkime>
doesn't seem to be a problem.
<houkime>
ok, will just choose a similar part but newer from the same manufacturer
<Joerg-Neo900>
optical design is critical
<houkime>
btw where it should go exactly?
<Joerg-Neo900>
the idea is stylus interrupts optical path
<houkime>
is there a hole in the case or sth which it should be under?
<Joerg-Neo900>
we covered it somewhere in whiteoaoers
<Joerg-Neo900>
papers
<houkime>
ok, will look up
<Joerg-Neo900>
and in stuff
<Joerg-Neo900>
it looks though apperture in PCB
<Joerg-Neo900>
refelction of beam on other wall of empty stylus bay. With stylus inserted path is blocked
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<houkime>
TMD26721TR-ND seems almost identical (and same wavelength)
<Joerg-Neo900>
sensor sits on S2 above stylus looking down through PCB hole S2->S1->stylusbay|reflector|stylusbay->S1-[2nd PCB hole]->S1->sensor-RX
<Joerg-Neo900>
check range
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<Joerg-Neo900>
needs to deal with range <10mm
<Joerg-Neo900>
or 15
<Joerg-Neo900>
and needs ultralow supply current since always-active
<Joerg-Neo900>
if those requerements can't be met, rather use a mechanical switch or omit stylus sensor all together
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<houkime>
it is calibrated at 100mm but can be programmed for other distances in 255 steps.
<houkime>
using different number of pulses
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<Joerg-Neo900>
as long as it detects a refexion of 7mm away objrct (wall of bay)...
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<houkime>
there are two variations in this family of sensors. TMD26721 like TMD26711 has i2c voltage = vdd. TMD26723 has i2c at fixed 1.8v
<houkime>
the part used in neo900 schematics is TMD26713 and it is powered from 2.7v
<houkime>
(ie a part with fixed 1.8v i2c from a previous family)
<houkime>
so the logical move is to employ TMD26723
<DocScrutinizer05>
:nod:
<houkime>
however availability of TMD26723 seems to be quite low. For example, on Digikey while the part is "active" there are 0 available immediately.
<DocScrutinizer05>
our daily business for almost a year, just we rarely did discuss it publicly
<DocScrutinizer05>
there's a lot more work in design than an occasional visitor would expect
<houkime>
most of neo900 parts are ok in this regard except for oldies that are needed for compat and that are sourced from original n900.
<houkime>
I am rechecking them as i go through courtyards and layout.
<Joerg-Neo900>
lis302 is EOL afaik
<Joerg-Neo900>
a few more as well
<Joerg-Neo900>
bq27200
<Joerg-Neo900>
wpwrak had a script to check *all* components
<houkime>
bq27200 will need to be sourced because it is a compatibility part((
<houkime>
we have already discussed this one earlier
<Joerg-Neo900>
well, leste isn't the 100% compatibility approach Neo900 was designed for. So it's questionable if this reqzurement is worth anything at all, adter all
<Joerg-Neo900>
unless you use genuine maemo dremantle, it won't matter
<Joerg-Neo900>
fremantle even
<houkime>
I checked ams website. Pretty much everything optical measuring which uses 1.8 i2c is out of stock.
<houkime>
however there was one more manufacturer that sdoes similar parts, called TAOS
<Joerg-Neo900>
We git some 3V3 I2C chips
<Joerg-Neo900>
thus a 3V3 bus, behind level shifter
<houkime>
ah, taos is just one of the ams's properties it seems.
<Joerg-Neo900>
those some other chips also were not available 1V8
<Joerg-Neo900>
sucks since it's just a logic level issue
<Joerg-Neo900>
I2C is OC
<Joerg-Neo900>
worts case use two FETs to levelshift I2C just for this chip
<Joerg-Neo900>
BOM +2 :-/
<Joerg-Neo900>
avctually +4, you need 2 pullup R too
<Joerg-Neo900>
see hackerbus whitepaper for discussion of FET levelshifters
<houkime>
3.3v should be ok
<Joerg-Neo900>
houkime: if you vould finf a simplr singlewire 1/0 sensor without any programming, this would be great. But seems they are not fasgionabke anymore