nishant pashine

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8 years, 8 months ago.

can anybody tell why my mbed adc is not working..??

If i run the potentiometer programm on pin 20 it gives me corresponding variable result on serial screen. But when i give any audio input and run the simple wave rec and play program on the same pin the file generates as empty..

kindly tell whether my adc section of mbed is gone or some other reason..

Depends on the voltage output of your audio

probably AC with no DC component so the Audio signal will go positive and negative with respect to 0V

so you need to confirm the voltage output of your audio signal as to Peak voltage levels.

Typical Line levels for Audio are 0.707Vrms this equates to a Peak Voltage of 1V and a Peak to Peak Voltage of 2Volts

If this is true in your case then just a potential divider with a capacitor (to ac-couple i.e. DC Block) should allow the ADC to read the range of the signal both Positve and Negative going.

If However your signal is much lower (in the mV range then some amplification is required; standard op-amp circuits are available on the web etc., You not seeing a result would indicate that the signal is low and you need to confirm this.

Welcome to the world of signal conditioning Kind Regards

posted by Martin Simpson 21 Aug 2015

Hi martin, thanks for the reply...c i need to record some tone of 5 sec, which i am recording via electret/condenser mic. i am using a mic pre-amplifier which is lm386 based.it works on 5v and i guess my output is not going beyond 3.3v... the circuit i used worked for a day and i was able to record with some hiss and hum... but now i am unable to record anything.. kindly help...

posted by nishant pashine 21 Aug 2015
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