Topic for #qi-hardware is now Copyleft hardware - http://qi-hardware.com | hardware hackers join here to discuss Ben NanoNote, atben / atusb 802.15.4 wireless, and other community driven hw projects | public logging at http://en.qi-hardware.com/irclogs
<kristianpaul>
wpwrak: the case fits on a atben?
<kristianpaul>
or are you getting ready to free memory sticks readers? ;-)
<kristianpaul>
but looks nice
<kristianpaul>
!
Fernandos has quit [#qi-hardware]
cladamw has joined #qi-hardware
<whitequark>
DocScrutinizer: could you hint me a case where a white noise generator is desirable?
<whitequark>
my intiution says there are enough valid ones to put a hw lfsr in a uC DAC, but I couldn't think of any
kristianpaul has joined #qi-hardware
kristianpaul has joined #qi-hardware
<DocScrutinizer51>
adjusting audio equipment
<whitequark>
ah. stupid me, ST has listed applications in the appnote
<whitequark>
"electronic music, <...> testing frequency response, sound masking with a Tinnitus masker
<whitequark>
and, er, "oversampling with white noise"?
<whitequark>
there's an AN link, but it is defunct :/
<DocScrutinizer51>
testing freq response was exatly what I meant
<whitequark>
DocScrutinizer: I don't quite get how you could ever _increase_ SNR by _adding white noise_
<DocScrutinizer51>
if you add white noise to a signal, then A/D convert it severla times, you can get higer accuracy than your ADconverter has digits/bits
<whitequark>
well, that's what it means. but why does it work that way?
<whitequark>
won't ADC give you better precision without noise?
<DocScrutinizer51>
statistics
<whitequark>
hm. like if the value is between two values, then by adding noise you "diffuse" it between the values and some measurements will show one and other ones another, and thus the average would be better?
<whitequark>
*two ADC presets, or how are they called
<DocScrutinizer51>
yep
<DocScrutinizer51>
it's basically dithering
<DocScrutinizer51>
if you get 90 probes N and 10 N+1, then your atual value is N+0.1
<whitequark>
ah, I got it. by adding white noise you increase the perceived resolution of ADC near your desired value, given that the value doesn't change more than zero "raw" ADC bits during the measurement
<DocScrutinizer51>
yes
<whitequark>
i.e. you could get the same by offseting the ADC with a DAC, but a white noise generator is way cheaper
<whitequark>
what a clever idea
<whitequark>
... wait, they generate white noise with a DAC
<whitequark>
and by not using a fixed sawtooth signal you average out any irregularities in the measurement
<whitequark>
seriously, this is incredibly clever.
<whitequark>
DocScrutinizer: am I right that for uninterrupted audio play with DMA I generally need two buffers, and when one empties I switch to another and fill the empty one?
<DocScrutinizer51>
,usually you do it that way
<DocScrutinizer51>
oftren with more than 2
<whitequark>
8k of RAM
<whitequark>
so, I think 2 are enough
rejon has joined #qi-hardware
xiangfu has joined #qi-hardware
<DocScrutinizer51>
depends on your source process' worst case latency
<DocScrutinizer51>
but I have to go back to sleep now, sorry
<whitequark>
ok, thanks a lot
<DocScrutinizer51>
YW :)
<DocScrutinizer51>
whitequark: check manpage of sox, I think there's also been a usecase of white noise added to improve sound (anti-aliasing)
<DocScrutinizer51>
or was it quantisation noise ?
<wpwrak>
kristianpaul: ah no, that's not for atben. i think atben would be best handled by some thin silicone coating. something as hydrophile as wood would be the last thing i'd consider for 2.4 GHz technology :) (alright, second to last. metal would be worse :)
<whitequark>
DocScrutinizer51: insomnia? :)
<whitequark>
btw you're right, it's to deter quantisation noise. basically the same thing as I understand it
<DocScrutinizer51>
indeed, each time the phone yells with highlight
panda|x201 has joined #qi-hardware
<whitequark>
wpwrak: I tried to put a logo (er, Aperture Science logo) on the case and utterly failed
<whitequark>
can you guess how? :)
<wpwrak>
on what case ?
<whitequark>
of my device
<whitequark>
which I try to make in a CAD
<whitequark>
and which will be laser cut
<wpwrak>
hmm. many possibilities of failure :)
<wpwrak>
ah, laser. that eliminates weak fixtures :)
<wpwrak>
laser cutting better than planned ? :)
<whitequark>
nah, not even a single run (thankfully)
<whitequark>
well, you know, there's some letters like A and R
<whitequark>
and P
<wpwrak>
i actually wonder what the tables of laser cutters are made of
<whitequark>
where you have a central element which would certainly fall out
<wpwrak>
several decades ago, people made forms for spray painting
<wpwrak>
they solved your problem :)
<whitequark>
yes. I seen them. but the letters with thin guides aren't so visually attractive as letters without them
<whitequark>
apart from that, laser tends to overheat thin parts afaik
<wpwrak>
ah, the hard choice between a flawed tangible result and an unattainable ideal :)
<whitequark>
so, er, I think I'll inscribe it, again with laser. every fab I seen offers both of the services. shouldn't be hard to convince them
<whitequark>
and it won't hurt if it'll get moved by a few mm away
<wpwrak>
yes, engraving is possible
<wpwrak>
we even have it on m1 :)
<whitequark>
yeah, I feel that my case will be a straight m1 case ripoff
<whitequark>
it even looks quite the same
<whitequark>
after a few iterations
<whitequark>
(the first one would just fall apart.)
<whitequark>
wpwrak: maybe you have any idea what format should I store 8K, 8-bit, 1-channel audio data?
<whitequark>
s,data?,data in?,
<whitequark>
ima adpcm is bigger than raw u8
<whitequark>
ah, nevermind, it is not. I specified wrong conversion settings
<wpwrak>
depends on many factors. like space constraints, what you do with it, processing capabilities, and so on
<wpwrak>
in general, the simpler, the better :) so WAV/u8 are great.
<whitequark>
not fitting into the flash
<whitequark>
and SPI flashes over 128k are somewhat more expensive/hard to get than I expected
<whitequark>
and I _really_ don't want to put an SD card in because of 160k of audio data
<wpwrak>
lower the sample rate ? ;-)
<whitequark>
under 8k? this degrades the quality substantially
<whitequark>
similarly I have no benefit of using >8k because: a) it's voice b) it's transmitted via gsm
<whitequark>
wpwrak: ADPCM decoder is like seriously huge
<whitequark>
with 118 bytes of code and 176 bytes of LUT
<whitequark>
wpwrak: also, have you considered using clang for your projects?
<whitequark>
for me it gives a 10% code size decrease over gcc, both being untweaked
<whitequark>
gcc is with -Os and clang is with -Os -flto
<DocScrutinizer>
wpwrak: HAH, your licky day with the characteristics of those particular LEDs you use. Some may easily start shining at < 1/3 nominal U(forward)
<DocScrutinizer>
lucky even
<wpwrak>
;-)
<DocScrutinizer>
esp when mixing e.g red and green or (God forvid) blue
<wpwrak>
yeah, with blue in the mix, abandon all hope :-)
<DocScrutinizer>
s/v/b
<qi-bot>
DocScrutinizer meant: "esp when mixing e.g red and green or (God forbid) blue"
<DocScrutinizer>
duh
<DocScrutinizer>
this bot is way too permissive
<wpwrak>
(bot) why ? it worked
<DocScrutinizer>
yeah, though it was meant not to do
<wpwrak>
;-)
<DocScrutinizer>
s/o/x
<qi-bot>
DocScrutinizer meant: "yeah, thxugh it was meant nxt tx dx"