Post by thread:[SX] Audio playback with SX & EEPROM

In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Has anyone ever tried this ? I'm wondering what the sound quality difference will be between using PWM and an RC filter with just one pin against using a 8-bit DAC ? A client of mine is intested in a circuit that will (among other things) playback a 10 second sound clip. I know there are circuits that will do just that, but the SX is going to be in the circuit anyway and I thought with just the cost of the EEPROM, a LM386 and a speaker I could do the sound too. He only needs telephone quality (8-bits @ 8KHz). This project is high volume(10K) and is very cost sensitive. So I would like to not use the DAC if possible. Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Jon Williams wrote:Since you're probably using a SX28 anyway, you could use RB or RC to output to an R2R DAC, couldn't you? This would be very cheap, and probably simplify program execution as you simply need to read the value from your EEPROM and write it to the port.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Chris Savage wrote:Bean, Before Sound Cards came down some of us used our Printer Port to make a cheap DAC using an R2R resistor network. It wasn't the greatest, but it worked. Given that I think your idea could too...It would really depend on the Read Speed of the EEPROM more than anything else I would guess.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Hey that's a good idea. It's nice to have cheap friends. The EEPROM is 400KHz so that shouldn't be a problem. Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, g_daubach wrote:Bean, you can find an example for a R2R resistor network DAC in my book (page 272).

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, PJMonty wrote:Bean, Actually, tons of CD players use pretty much this exact approach (PWM) and they sound great. I think they are called sigma-delta convertors, and basically what you have to do is tradeoff DAC speed for bits. In other words, these convertors typically run at 256X the normal conversion rate. The idea is to output such a huge number of 1s and 0s that when integrated it sounds like normal audio. Take a look at the following (note that these just seemed like promising Google hits - I haven't actually read them myself): http://www.embedded.com/showArticle.jhtml?articleID=22101730 http://www.analog.com/UploadedFiles/Presentations/1496341255ICCE.pdf http://www.maxim-ic.com/appnotes.cfm/appnote_number/1870 The last one is actually about ADC, but I think it may have relevant info.

[list]Thanks, PeterM[/list] ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=107741#m107792 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)

In SX Microcontrollers, SX/B Compiler and SX-Key Tool, George Herzog wrote:Myke Predko in one of his major microcontroller books {okay, the PIC book} takes the position that using them to create sound is just about one of their worst uses. My own experience with using a 'talking dictionary' to learn Chinese is that it seems to have a major nasal problem. The sound itself is not the problem, it is the retention of the overtones and all the color. It seems the better your DAC, the more faithful the sould. Sampling at 256x the normal converson rate seems very appropriate, but huge.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Chris Savage wrote:Bean, You could always build a prototype and try the R2R method I mentioned. If Guenther has an example all the better. It really depends on the quality you are looking for. I don't think they're that bad, but I am not comparing it to my SB Audigy 2 ZS Sound Card. I am comparing to an ISD chip or something more that quality of sound. It would, in all likelihood sound much better.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Beau Schwabe wrote:Bean, Here is a forgotten but not lost archive of mine from my old web page... http://webpages.charter.net/schwabelove/BasicStamp/wavprom.gif ...it's only 2.9 seconds at 11kHz 8-bit mono, but it's only using a 32k EPROM. You can always add more memory, or lower the quality to 8kHz ( I wouldn't go much lower ) It was great for putting in sound bytes with things like.... " 'Beep' 'Beep' 'Beep' Kirk to enterprise " ...The only thing you need to do to the WAV file is to strip off the 54 byte header. Even this isn't critical, if you don't, you just hear a "Pop" at the beginning of the audio. I usually did this from the burner software.... visually you can see this location in the HEX table by a series of 7F and 80 numbers representing the audio midpoint.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, lordsteve wrote:Cost sensitive? I think the SX would excel at this...

http://www.romanblack.com/picsound.htm ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=107741#m107859 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)

In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Chris Savage wrote:

Lord Steve, Very nice. Thanks for the information. Bean could easily implement that! =) ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=107741#m107865 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)

In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Beau Schwabe wrote:Lord Steve, Golf Clap!! Very nice!!

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Thanks everyone. I had found the picsound site, but hadn't really examined it. Look interesting. I'll have to give it a try. Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, william wrote:Mr Bean, I would advise that you place an op-amp based (TL082 ? ) active low pass filter to clean out the voice before it goes into the audio amplifier. This way you can even use 1pin PWM output safely without using the whole 8 pin port.

Sorry to have to recommend additional costs. : ( ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=107741#m108102 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)

In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:I tried the samples from picsound and I don't think they are going to be good enough. You cannot change the playback sample rate so it's hard to tell it that would make much difference. I may have to use either a serial dac or a shiftreg (they want 16 LEDs also). Just great, more parts... Maybe I can talk them into only 8 LEDs ? P.S. Does anyone know where to get really thin speakers ? Something like 1" to 1.5" diameter but less than 0.20" thick ? Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Beau Schwabe wrote:There is a local electronic surplus store near me that has a few bins of these. I believe that they were originally designed for use in a modem.

I can check sometime during the week for a price if you would like.... (only open Monday - Friday) ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=107741#m108167 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)

In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Beau, Thanks for the offer, but I need a supply of 10K to 50K (over a couple years) for this client. It's basically a take on the old "greeting card that plays sound" idea. Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Coriolis wrote:How about piezo disk speakers, they are thin and cheap.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, lordsteve wrote:Hey, Bean. What did you mean when you said that you can't change the playback sample rate? You can play it at whatever sample rate you want, just has to be encoded in that sample rate.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Steve, I was talking about the PICSOUND program that runs on the PC. It always playsback at 15625Hz. I would have liked to tried a higher sample rate to see if the audio sounded any better, but I don't see any option to change it. Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Beau Schwabe wrote:Bean!! I think I found some speakers that might work for you.... I forgot I had these (originally in an old laptop). SAM SUNG 2001 N837 These measure 20mm diameter by 3mm height.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Beau, Cool I would love to try them. I never thought about notebook speakers. Do you need my address ? Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Beau Schwabe wrote:

Bean, Send me a PM or E-mail with your address, and I will try to get them out to you tomorrow (Tuesday) ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=107741#m108380 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)

In SX Microcontrollers, SX/B Compiler and SX-Key Tool, KenLem wrote:Hi Bean, I have C program that reads Microsoft wav files and writes out a C header file of the audio data. It will do the conversion from whatever compression is used in the wav file to PCM automatically. Let me know if you'd like it. I use it for a project involving another microprocessor that has an on-board 8 bit DAC and internal analog low pass filter. The sound quality is excellant.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:KenLem, Yes I love to see the code. You wouldn't have a schematic for the audio output would you ? Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, KenLem wrote:I'll post the code and schematic tonight when I get home. The schematic won't help you much since it's just two pins connected to a speaker with a 33ohm resistor to ground on one of the pins. The 16 bit version requires an external low pass filter.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, chiphead wrote:Bean; If you're still after speakers, you might want to also look at model railroad sites for speakers used for onboard sound. One "leading manufacturer" is http://www.soundtraxx.com/ With the quantities you're after I wouldn't buy from them, but they may be able to direct you to thier source, or you could buy a speaker or two and get the name/number off it (hopefully). I haven't had a chance to use this stuff, but I've seen/heard it at shows, and they are getting some very good sound out of these units.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, KenLem wrote:Here is the schematic for both the 8 bit and 16 bit version. I have attached and exe that converts wave files to .h files. I have attached source. You'll note that the write routine is hard coded for 8bit @16Khz. It should be simple to change. I had to rip it out of another project. I hope to improve on the program in the future but it's rough.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, kd5dhu wrote:Bean, Found these speakers:

http://www.goldmine-elec-products.com/prodinfo.asp?number=G13674&variation=&aitem=2&mitem=25 Mike ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=2&m=107741#m108924 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)

In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Mike, Thanks for those links. I'll check them out. Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Is anyone familar with .WAV files ? I downloaded a .WAV file (8-bit 8000 samples per second). When I just put the data onto a DAC I can hear the sound, but there is what sounds like a constant tone in the sound. I realize there is a header that would have some non-sound info, but is it possible that there is non-sound info WITHIN the data bytes ? I'm using the old "You've got mail" wav file. I can post it if anyone wants to examine it. Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Beau Schwabe wrote:Silly question, is the constant tone high pitched? ...Anywhere near 8kHz? If so, you might need a simple RC filter that rolls-off right at or near 8kHz.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Beau, No, it's like a "motor boating" type sound. Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Beau Schwabe wrote: [Quoting: "Bean"] 8-bit 8000 samples per second Another thought.... Is it Stereo or Mono? If not , you should convert it to Mono. [Quoting: "Bean"] When I just put the data onto a DAC I can hear the sound Does the playback "rate" seem to be correct or is it about half the speed that you would expect? This could be another indication the audio clip is Stereo vs. Mono.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Beau, It is mono and the playback rate seems to be okay. I saw in the .WAV spec that there are "chunks". Are most sound files just 1 big chunk ? Or do they break the file into a series of smaller "chunks" ? Bean.

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In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Beau Schwabe wrote:Bean, For 8-Bit Mono, unless things have changed, once you get past the 44 byte header, the remaining data is RAW audio with 127 equal to the audio "null".

Reference: http://www.technology.niagarac.on.ca/courses/ctec1631/WavFileFormat.html ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=2&m=107741#m113140 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2006 (http://www.dotNetBB.com)

In SX Microcontrollers, SX/B Compiler and SX-Key Tool, bean wrote:Beau, Thanks for the info. After convincing myself that it wasn't "in-the-data" I found a program bug. So.... IT WORKS!!! And the 4-bit DAC isn't that bad. I'm cheating and not even using an audio amp, just low values for the R2R (100 & 200 ohm resistors). I have a 64KB eeprom, so if I store the samples as nibbles @ 8KHz I can store and playback 16 seconds of sound. Pretty cool. I'll have to post this in the project section when I get it further along... Bean.

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