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ISD17XX (ISD1700) series problems

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babylon

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I am writing microcontroller code for ISD17XX (really ISD17240) series chip corders.

I am applying PC sound card output to ANAIn input of ISD. When I use FT to pass input signal to the output, sound quality is very good. When I record that sound and play it from the chip, the quality of recorded sound is awful! Any suggestion? I have changed my chip, but nothing changed. (Circuit is on bread board).

Thanks
Magic
 
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eforman

New Member
i'm having the exact same problem. i'm using a standard 8-ohm speaker direct to pins SPK- and SPK+. i have added decoupling caps everywhere as recommended, but doesn't fix problem. my chip is on a breadboard, so i don't really have Vss-a (analog ground) and Vss-d (digital ground) isolated, they are connected of course, i tried to get one on one side, one on the other, but it doesn't seem to affect anything.

i suspect the issue is related to these instructions in the Design Guide:

"separate each power line and each ground path individually from device to system. meanwhile, ISD1700 has isolated Vccp, Vssp1 & Vssp2 pads for PWM speaker driver. to minimize noise from speaker driver, it is vital to route an independent trace from each related pin to the supply and ground terminals directly."

but not sure how to implement this on a small breadboard.

http://www.nuvoton-usa.com/products/isd_products/chipcorder/applicationbriefs/AN-CC1002.pdf

some other things i've noticed which might give someone an idea -

- when (battery powered) ipod plugged into ANA-IN, feed-through sound is fairly clear and loud, but when recorded/played sounds terrible, not only very noisy but also a lot quieter

- when computer sound-out plugged into ANA-IN, both feed-through sound and playback are terrible (ground loop?)

- when ANA-IN left unplugged, feed-through sound is very noisy

- when recording from iPod with (clean, loud) feed-through, result is audible, albeit crappy. when recording from iPod with feed-through OFF, result is almost inaudibly low in volume.

- on the demo board schematic, the ANA-IN is pulled down to ground with a 5k resistor before the coupling capacitor and sound input line. when i put this in, the noise on the feed-through is silenced but so is the audio - nothing plays through or is recorded.

i also studied the demo board schematic to give me clues on good layout practice, but again not sure exactly how to translate best into breadboard:

http://www.nuvoton.com/NR/rdonlyres...9020CA581188/0/ISD_ES17xxUSB_PB_UserGuide.pdf
 

eforman

New Member
hmm, i might have found the problem. it seems the chip comes with ANA-IN disabled?! you have to use a microphone or instruct it with SPI to re-enable ANA-IN. see this thread:
ISD1700 series Winbond chipcorder - MEL PICBASIC Forum

"The Winbond website and the ISD1700 datasheet frequently say "For technical details, please refer to the Design Guide". That is NOT the "AN-CC1002 Design Considerations for ISD1700 Family.pdf" document that is available on their website! In order to get the "Design Guide" (I1700 Design Guide Rev 1.1.pdf) I had to email them and request it. That is the only document I've found that bothers to tell you that the devices come from the factory with the AnaIn input and the Aux (Voltage) output disabled in pushbutton mode.

In order to reprogram the device's analog path configuration, you need to use the SPI interface. If you need more info on that, or have any other questions, let me know."
 

John_mich

New Member
In standalone mode, try pressing FT together with REC during recording. FT will enable ANAin. ANAin by default is disabled.


I am writing microcontroller code for ISD17XX (really ISD17240) series chip corders.

I am applying PC sound card output to ANAIn input of ISD. When I use FT to pass input signal to the output, sound quality is very good. When I record that sound and play it from the chip, the quality of recorded sound is awful! Any suggestion? I have changed my chip, but nothing changed. (Circuit is on bread board).

Thanks
Magic
 

vinniewryan

New Member
Sorry to bring up an old topic, but for those of you searching for the answer, John_mich's solution (above) worked like a charm! I remember trying to figure this out about a year ago and now I'm using the ISD1700 again for a new project.
 
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