On Fri, 21 Oct 2016 22:47:36 +0000, Steve Pope wrote:> Tim Wescott <seemywebsite@myfooter.really> wrote: > >>One way or another you need to filter the signal a lot more strongly >>than you'll achieve with just one integration. > > Yep > >>Basically, your integrator provides one pole of filtering; you need four >>or five in total. > > Yep > >>I think we can help you out, when you're open to doing something more >>than a simple one-stage filter. > > I'll nitpick -- there may be a "one stage" filter that is good enough. > I have used all-pole, 4th order low pass filters that are implemented in > a single stage (direct form).It's Friday. I've been thinking all week. I meant "pole" -- I think I was thinking in radio-frequency design terms, where one "stage" is one resonator. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com I'm looking for work -- see my website!
Integrate PDM to PCM?
Started by ●October 13, 2016
Reply by ●October 21, 20162016-10-21
Reply by ●October 21, 20162016-10-21
> ... solder those tiny mics yourself...No, thankfully Knowles can provide samples on passive "coupon" boards that have a five-conductor standard 4mm-centers edge connector. Tiny, indeed. Two-pin 0.1" for reference: https://www.dropbox.com/s/lgddqg4vldbu9dj/KnowlesCoupon.jpg> ... Wolfson Audio card for Raspberry Pi...A natural - if it took PDM in. Tom
Reply by ●October 22, 20162016-10-22
> ... solder those tiny mics yourself...No, thankfully Knowles can provide samples on passive "coupon" boards that have a five-conductor standard 4mm-centers edge connector. Tiny, indeed. Two-pin 0.1" for reference: > ... solder those tiny mics yourself... No, thankfully Knowles can provide samples on passive "coupon" boards that have a five-conductor standard 4mm-centers edge connector. Tiny, indeed. Two-pin 0.1" for reference: > ... solder those tiny mics yourself... No, thankfully Knowles can provide samples on passive "coupon" boards that have a five-conductor standard 4mm-centers edge connector. Tiny, indeed. Two-pin 0.1" for reference: https://www.dropbox.com/s/rndx30dda7w3ztw/KnowlesCoupon.jpg?dl=0> ... Wolfson Audio card for Raspberry Pi...A natural - if it took PDM in. Tom> ... Wolfson Audio card for Raspberry Pi...A natural - if it took PDM in. Tom> ... Wolfson Audio card for Raspberry Pi...A natural - if it took PDM in. Tom
Reply by ●October 22, 20162016-10-22
> ... solder those tiny mics yourself...No, thankfully Knowles can provide samples on passive "coupon" boards that have a five-conductor standard 4mm-centers edge connector. Tiny, indeed. Two-pin 0.1" for reference: https://www.dropbox.com/s/rndx30dda7w3ztw/KnowlesCoupon.jpg?dl=0> ... Wolfson Audio card for Raspberry Pi...A natural - if it took PDM in. Tom
Reply by ●October 22, 20162016-10-22
On Friday, October 21, 2016 at 11:50:27 PM UTC-4, Tom Becker wrote:> > ... solder those tiny mics yourself... > > No, thankfully Knowles can provide samples on passive "coupon" boards that have a five-conductor standard 4mm-centers edge connector. Tiny, indeed. Two-pin 0.1" for reference: https://www.dropbox.com/s/rndx30dda7w3ztw/KnowlesCoupon.jpg?dl=0 > > > ... Wolfson Audio card for Raspberry Pi... > > A natural - if it took PDM in. > > > Tom>>> No, thankfully Knowles can provide samples on passive "coupon" boardsHow many samples can they provide and how much do they charge per board ? I'be seen some manufacturers charging as much as 80 bucks for a simple soldered on the board mic "sample" (no preamp, no nothing, just mic) thanks, but no thanks (but still a better deal than trying to solder it yourself which is pretty much impossible)> > ... Wolfson Audio card for Raspberry Pi... > > A natural - if it took PDM in.As far as I remember Wolfson has 2 high quality digital MEMS microphones soldered to the main board interfaced to their DSP with all of this PDM crap being taken care for you :-) If you just want to make some high quality bat recordings then save yourself from all the trouble and go Wolfson (or similar) route
Reply by ●October 22, 20162016-10-22
> ... Wolfson...It's a Cirrus board now. https://www.element14.com/community/servlet/JiveServlet/previewBody/74257-102-1-309528/Cirrus%20Logic%20Audio%20Card%20for%20B%2B%20and%20A%2B%20onwards%20V1.02.pdf> ... has 2 [] digital MEMS microphones...Yes, but again only characterized to 10kHz. http://www.element14.com/community/servlet/JiveServlet/downloadBody/65687-102-1-288319/WM7220.pdf It looks like a good 192kHz analog sound card for the RPi, though. Tom
Reply by ●October 22, 20162016-10-22
On Saturday, October 22, 2016 at 5:40:12 AM UTC-4, Tom Becker wrote:> > ... Wolfson... >=20 > It's a Cirrus board now. https://www.element14.com/community/servlet/Jiv=eServlet/previewBody/74257-102-1-309528/Cirrus%20Logic%20Audio%20Card%20for= %20B%2B%20and%20A%2B%20onwards%20V1.02.pdf>=20 > > ... has 2 [] digital MEMS microphones... >=20 > Yes, but again only characterized to 10kHz. >=20 > http://www.element14.com/community/servlet/JiveServlet/downloadBody/65687=-102-1-288319/WM7220.pdf>=20 > It looks like a good 192kHz analog sound card for the RPi, though. >=20 >=20 > TomPeople have used Wolfson card for bat recordings with good success. Here is just one quick google search result: http://www.afraidofsunlight.co.uk/weather/public/Pi%20Bat%20Call%20Recorder= .pdf (not sure why he uses external electrets - the onboard mics are high-q= uality MEMS mics) Card is good for recording, maybe for streaming too, but if you need to do = something else then you are on your own:)=20 For university-type of research I would use some high-quality data acquisit= ion card or USB DAQ device e.g from National Instruments, with high-quality= analog microphones, preamps and PC or laptop running controlling software = program (e.g in Matlab) - be prepared to shell out some $$$$ =20 Let us know about the path you take and how it goes...
Reply by ●October 22, 20162016-10-22
Thanks for the link. I've been recording bat calls for years and some of the data has made it into academic literature. I choose to make my own mics; instead of spending major money buying commercial bat sensor systems and software, I choose to enjoy wasting large amounts of time developing my own. In the field I currently use a pair of 14-element phantom-powered electret pressure arrays feeding good preamps and an RPi; another pair of them is permanently mounted above water in Cape Coral and yields audio - shifted -22kHz at the moment - that's streamed at http://78.46.38.217/amb9u; http://78.46.38.217/amb9 is unshifted. Windy today.> Let us know about the path you take and how it goes...Initial AVR counter results are forthcoming. Tom
Reply by ●October 22, 20162016-10-22
On Sat, 22 Oct 2016 11:18:39 -0700, Tom Becker wrote:> Thanks for the link. > > I've been recording bat calls for years and some of the data has made it > into academic literature. I choose to make my own mics; instead of > spending major money buying commercial bat sensor systems and software, > I choose to enjoy wasting large amounts of time developing my own. > > In the field I currently use a pair of 14-element phantom-powered > electret pressure arrays feeding good preamps and an RPi; another pair > of them is permanently mounted above water in Cape Coral and yields > audio - shifted -22kHz at the moment - that's streamed at > http://78.46.38.217/amb9u; http://78.46.38.217/amb9 is unshifted. Windy > today. > >> Let us know about the path you take and how it goes... > > Initial AVR counter results are forthcoming. > > > TomWell, so much for suggesting that you buy electret elements and roll your own preamp... Have you tried making your own elements? -- www.wescottdesign.com
Reply by ●October 22, 20162016-10-22
> Have you tried making your own elements?No, but maybe someday I'll tinker with a 30mm Polaroid 200V electrostatic but I am, for now, put off by the patterns that large-diaphragm sensors exhibit. High voltage is surely also more problematic. I don't want narrow lobes. I enjoy recording in stereo to hear the bat flight dynamics; omnidirectional, figure-eight and cardioid patterns, sometimes recorded in Mid-Side which allows manipulating the pattern later, suit that well. Most government, commercial and academic bat freaks are seeking species identification and population counts best achieved with more directional mics (for which more than one company gets $1200 each: http://www.ultrasoundgate.com, for example). The equipment is often exposed to dew that requires conformal coating and heaters to combat. My mics have eight resistors that warm the assembly to prevent condensation and consequential corrosion - an instant serious noise generator - and that's at 12-48V. I expect 200V must be a PITA. Tom
