wolfspraul | Artyom (in absence) thanks a lot for detailing all your thoughts and decision making process! | 01:55 |
---|---|---|
wolfspraul | that's very helpful to understand... | 01:55 |
wolfspraul | I didn't understand what judgment of mine you referred to though - did I say anything? | 01:56 |
wolfspraul | I planned to email the Qi list pointing to your great blog post, but haven't done that yet... | 01:56 |
wolfspraul | anyway, all good. thanks for the background info! | 01:56 |
wpwrak | whitequark: no idea. try and find out ;-) i wouldn't expect very visible damage. and it may be at a hidden layer. but you never know ... | 02:02 |
kristianpaul | indeed, Reliaility ! | 03:15 |
Artyom | wolfsraul: I meant this statement: "wolfsprauldismissing arm is not smart and good imho". May be I just didn't understand the meaning correctly. But anyway I decided to explain why I had switched to MM SoC and put ARM away for some time. | 03:58 |
wolfspraul | ah | 04:08 |
wolfspraul | :-) | 04:08 |
wolfspraul | that was in NO WAY at all a reference to you | 04:08 |
wolfspraul | in fact you are very balanced and objective in comparing all this, which helps me (and others I think) | 04:09 |
wolfspraul | it's more a reminder to self to appreciate what ARM has done (and keeps doing), and take Milkymist to the next level, instead of trying to catch up | 04:11 |
wolfspraul | and of course, your findings may take you back to ARM, and why not? | 04:11 |
wolfspraul | we are passionate about making things work, I think | 04:11 |
wolfspraul | I would do that too, I want to get stuff to work... | 04:11 |
wolfspraul | meanwhile we improve Milkymist SoC, which will eventually be chosen because IT IS the best, not because it's a dogmatic choice | 04:12 |
Artyom | wolfspraul: I think we undertand each other fine now :) As I said I could misunderstand the true meaning of your statement ;) | 04:20 |
whitequark | can anyone answer a relatively simple question? | 10:14 |
whitequark | http://electronics.stackexchange.com/questions/27452/coupling-electret-microphone-input-to-linear-audio-output | 10:15 |
whitequark | DocScrutinizer: maybe you know? | 10:15 |
DocScrutinizer51 | whitequark: maybe I can answer, but only qhwn you pose the question here | 14:59 |
DocScrutinizer51 | when* | 14:59 |
DocScrutinizer51 | no way I'll open a webpage to rea it now, on mobile | 15:00 |
DocScrutinizer51 | anyway the URL suggests you want to plug mic-in to errr line-out? | 15:01 |
DocScrutinizer51 | PLRASE KILL E!! | 16:10 |
DocScrutinizer51 | ME | 16:11 |
DocScrutinizer51 | or rather, kill billyboy gates | 16:11 |
Action: DocScrutinizer51 can't stop headdesking | 16:12 | |
DocScrutinizer51 | c:\foo\bar\boo\CPU-A\conf\brd.cfg gets displayed in sourceinsight as brd.cfg[c:\foo\bar\...\conf\] | 16:14 |
DocScrutinizer51 | BUT THERE'S ALSO CPU-B!!! | 16:15 |
DocScrutinizer51 | guess what's display for cpu-b brs.cfg file in source-inight | 16:16 |
Action: DocScrutinizer51 continues headdesking, while pondering suicide or 500kg TNT | 16:17 | |
DocScrutinizer | in explorer you got a decent full pathname in top addr textbox. Not so in "Open" and "Save as" dialogs :-((( | 19:19 |
DocScrutinizer | FSK wincrap! | 19:19 |
DocScrutinizer | +C | 19:20 |
DocScrutinizer | is there any tool to resize non-resizable dialogs, on windoze? | 19:21 |
DocScrutinizer | prolly not, and even if you could resize the "window" of that dialog, I'd bet the widgets inside won't resize accordingly - unless the unlikely luccky case the requester is coded in Qt | 19:24 |
whitequark | oh, was afk | 19:25 |
whitequark | DocScrutinizer: yeah, I have a GSM module with line-out and mic-in (electret) | 19:25 |
whitequark | actually, two modules | 19:25 |
DocScrutinizer | :nod: | 19:25 |
whitequark | and I want to plug the line-out of one to mic-in of another | 19:26 |
whitequark | should be pretty trivial, but I was unable to google it | 19:26 |
whitequark | bonus points for not letting TDMA noise to the line | 19:26 |
whitequark | both the line-out and mic-in are differential | 19:27 |
DocScrutinizer | use a R-divider to attenuate, with a 2kR across the mic lines and a 50..1000kR series to line, in series with a 100nF decoupling C | 19:27 |
DocScrutinizer | use a 1k load R across line-out | 19:28 |
DocScrutinizer | for the TDMA noise, you might or might not run into problems. Worst case you need a NF-transformer | 19:31 |
DocScrutinizer | but then, you as well can use some active circuitry, like e.g an optocoupler | 19:32 |
whitequark | ah. I thought that I could just use coaxial cables (I have a lot of these) for connecting the audio i/o to a shielded board | 19:34 |
DocScrutinizer | depending on particular line-out differential design, you might already have sufficient bias on one of the lines to GND, to drive the opto's LED with just a series R as external components | 19:34 |
whitequark | not sure if that would help actually | 19:35 |
DocScrutinizer | whitequark: regarding TDMA noise your main problem is common GND of both modules | 19:35 |
DocScrutinizer | the TX draws massive current bursts and thus introduces TDMA noise floor to its own GND level and in turn also to all inputs and outputs | 19:36 |
whitequark | my attempt at schematics: http://higgs.rghost.ru/36815621.image | 19:37 |
whitequark | have I got it right? | 19:37 |
DocScrutinizer | of course the differential input on the other module is meant to suppress those common mode noise components in signal | 19:37 |
DocScrutinizer | but that usually doesn't pan out | 19:38 |
DocScrutinizer | (right?) err, yup, just common GND missing at bottom | 19:38 |
DocScrutinizer | one line + | 19:38 |
whitequark | yes, about common gnd | 19:39 |
whitequark | with this scheme, I just connect LINE- to MIC-, right? | 19:39 |
whitequark | and they're not connected to the GND of the modules | 19:39 |
whitequark | thus they're not affected by noise floor | 19:39 |
DocScrutinizer | yes | 19:40 |
DocScrutinizer | but they are still affected by noise on TX module's GND as it will "lift" whole circuit's GND reference level | 19:40 |
DocScrutinizer | so both Line+ and Line- will have common mode noise | 19:41 |
whitequark | hm, yes, but how differential input won't reduce that to zero? | 19:41 |
DocScrutinizer | an ideal differential input will actually do that | 19:43 |
DocScrutinizer | problem is most of those "differential" inputs are not perfectly balanced | 19:44 |
whitequark | oh, the non-ideality of electronics ruining our clevermost plans... | 19:45 |
whitequark | if that would be the worst case, is an NF-transformer something like I could just go, buy and solder in? | 19:46 |
DocScrutinizer | ooh, and you want a 100nF in your GND connection as well | 19:46 |
DocScrutinizer | yup | 19:46 |
whitequark | so, http://rghost.ru/36815801.view | 19:47 |
whitequark | cool, thanks. I'll buy the components tomorrow and assemble the device | 19:48 |
whitequark | ah, one more thing | 19:48 |
whitequark | the module has SMT antenna pads, so they recommend to lay out a PCB, then calculate a 50 Ohm trace and so on | 19:48 |
whitequark | I'm going to wire-wrap the entire device, so I want to buy a 50 Ohm antenna with a cable, cut its SMA connector off and just solder it directly to pads | 19:49 |
whitequark | would that work? | 19:49 |
DocScrutinizer | should | 19:50 |
whitequark | ok thanks again. I need to run now | 19:51 |
DocScrutinizer | if it's an unbalanced 50Ohm output, I.E. one of the two pads is GND | 19:51 |
DocScrutinizer | whitequark: you should calculate R2 so it attenuates your line-out level to sth like 100mV for 2k mic load R | 19:54 |
DocScrutinizer | err R1 | 19:54 |
DocScrutinizer | for R1 you might reconsider 1k according to properties of your line-out. If that's e.g. no line-out but a dedicated speaker output, you may need a 100R rather than 1k, maybe even a 33R though I doubt the line-out amp is that picky | 19:56 |
DocScrutinizer | 1k is proper load for standard line-out as found on any arbitrary home audio equipment | 19:56 |
DocScrutinizer | standard line-out maybe 2Vss, so R1=50k | 19:57 |
DocScrutinizer | poti should be log type | 19:59 |
DocScrutinizer | with the spead end (the origin) towards mic- | 20:02 |
DocScrutinizer | spread | 20:02 |
DocScrutinizer | whitequark: (trafo) http://www.conrad.de/ce/de/product/516201/ | 20:33 |
whitequark | (antenna output) yes, it's unbalanced | 20:39 |
whitequark | (line-out) it can drive a speaker directly if it's not very powerful (a headphone), or they also have an example with additional amp | 20:40 |
whitequark | Load Resistance (typ) is 32 Ohm | 20:40 |
whitequark | and the diff. swing is 2.2V | 20:40 |
whitequark | *Vpp | 20:41 |
whitequark | as per the mic in, its working voltage is 1.5V, and diff. input voltage should be 740mV RMS to keep THD <5%@1kHz | 20:42 |
whitequark | at 0dB | 20:42 |
whitequark | and 15.9 mV rms at 20dB | 20:42 |
whitequark | I guess I should drive it with higher voltage, as the amp would add more noise at greater attenuation levels, right? | 20:43 |
whitequark | (http://www.8051projects.net/e107_files/public/1300865705_32137_FT45814_sim900d_hd_v1.02.pdf, page 43) | 20:46 |
--- Sat Mar 3 2012 | 00:00 |
Generated by irclog2html.py 2.9.2 by Marius Gedminas - find it at mg.pov.lt!