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Beginner on DSP?

I asked a question with subject "Voice Recorder?" a few days ago.

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But I can't explain the question (again :) ) The Voice Recorder is a part of my project on university. Actually I want to learn how voice is inputted to MCU and how it is processed?

After that message, I searched the Internet again. I found some books like The Scientist and Engineer's Guide to Digital Signal Processing

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I'm going to process telephone quality speech on MCU. In the book, for telephone quality speech sampling bit rate is gaven as 8kHz, and number of bits is gaven as 8-bit on page

359(ch22) . I have questions on this :

  1. If i process sounds on a 8 bit MCU like 8051, is there any loss of voice or are there any disadvantages?

  1. Do I have to use an Digital Signal Processor?
  2. How much Clock Frequency do i need? Can i make it with a 40MHz MCU?
  3. Can you advice me DSP books, if you think i have to learn it to make this recorder?

Thanks again. I hope I could explain with this message :)

Reply to
Tolga Onbay
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This isn't really a signal *processing* problem - you're not actually doing any processing of the voice data at all - simply sampling the data and storing it, then playing it back again.

So I can't see why you'd need a DSP!

The quality of the voice is determined by two factors - the resolution of the A/D conversion and the sampling rate.

The speed of the processor is, to a point, irrelevant. You just need to ensure that the speed of the A/D converter is fast enough for your desired sampling rate, and that your MCU has enough time to store samples and setup for the next sample.

40MHz/8kHz = 5000 cycles. Assuming 4 cycles/instruction that's still 1250 instructions between samples. Plenty. Now you just need to check the bandwidth of the A/D on this MCU.

Now you just have to worry about playback - D/A conversion. Plenty of DACs avilable to do that, if your MCU hasn't got one.

Regards, Mark

Reply to
Mark McDougall

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I suggest posting to comp.dsp . They are good at helping you define your question and then answering it.

Reply to
Richard Owlett

I'm going to process telephone quality

Select the "Tools" tab Select the "Tooltree" tab Select the "Appnote" list item Select the "I/O Applications" Select the AVR335: Digital Sound Recorder with AVR and Serial DataFlash Download app note and code.

In order to use the AVR, you probably need to download the free tools: * AVR Studio * WinAVR

Links to both above can be found on

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You need an AVR programmer.

If you talk to your professor, he can request a free set of AVR tools (Devboards/programmer + JTAG emulator) as part of the Atmel University program.

Using onchip ADC gives you low quality voice. For a high quality voice recorder, you want to have an external Voice Codec. Most MCUs does not have an appropriate interface to a voice codec. The AT91SAM7S32 is a low end MCU which is based on the ARM core which has a synchronous serial controller that can be interfaced to an I2S codec.

Reply to
Ulf Samuelsson

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