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PCM1803A - Please help

Benoit St-Jean
Expert 1030 points
Other Parts Discussed in Thread: PCM1803, DIT4192

This is my second post. I've posted a message last week but I think it got lost because I can't find it.

I'm trying to make sense of the spec sheets for this device. I have a few questions...

So, my setup seems to be working but I have no way of testing the digital audio output so far. I might implement saving the data to an SD card but I have a few questions before I start doing that. My circuit consists of a PIC18F4620 device with a PWM output of 2.5 MHz. I can see that fine on my oscilloscope. Connecting my scope to the DOUT pin on the PCM1803, I see data. I believe the data is fine since if I leave the input floating and touch the wire tied to it, the static noise is what seems to be converted. If I ground the output, I see a single recurring peak which is most likely a single bit of data.

1) If I was to find an A/V device such as a home stereo amplifier with an S/PDIF input, would I technically be able to hear the data out of my PCM1803 if I connect it to the S/PDIF input?

2) How can I test the DOUT data if I don't have a D/A converter?

3) What is the lowest audio quality I can setup on the PCM1803 and how do I do it? Do I simply need to lower the frequency of the PWM?

Lowering the audio quality to the lowest possible quality will at least enable me to manipulate the data and parse it or save it to an SD card. I am new to A/D audio converters and I'd appreciate some help and pointers.

Again, I *think* that my circuit is working but I don't know how to test the data. I guess I could try with different fixed voltage values on the input and see what kind of result I get but hearing the actual audio would be ideal. If you wish to answer by email (and I can afterwards post the solution here), my email is benoit.st.jean[AT]rogers.com.

Thanks!

  • 0
    TI__Genius 16270 points

    Benoit,

    What is the input exactly to the PCM1803?  In order for the PCM1803 to provide S/PDIF output, a part such as the DIT4192 would be needed to convert the output to S/PDIF.  But if that was done then audio should be able to be heard using an S/PDIF input amplifier.   In terms of lowest audio quality, the part is a 24-bit ADC so 24 bits will be the output. 

  • 0 in reply to Patrick Galvin
    Expert 1030 points

    Hello Patrick,

    Here are the specs from TI's website (second line is voltage input):

    • 24-Bit Delta-Sigma Stereo A/D Converter
    • Single-Ended Voltage Input: 3 Vp-p
    • Oversampling Decimation Filter:
      • Oversampling Frequency: ×64, ×128
      • Pass-Band Ripple: ±0.05 dB
      • Stop-Band Attenuation: -65 dB
      • On-Chip High-Pass Filter: 0.84 Hz (44.1 kHz)
    • High-Performance:
      • THD+N: -95 dB (Typically)
      • SNR: 103 dB (Typically)
      • Dynamic Range: 103 dB (Typically)
    • PCM Audio Interface:
      • Master/Slave Mode Selectable
      • Data Formats:
        • 24-Bit Left-Justified
        • 24-Bit I2S
        • 20-, 24-Bit Right-Justified
    • Sampling Rate: 16 kHz to 96 kHz
    • System Clock: 256 fS, 384 fS, 512 fS, 768 fS
    • Dual Power Supplies: 5 V for Analog, 3.3 V for Digital

    Benoit

  • 0 in reply to Benoit St-Jean
    TI__Genius 16270 points

    Benoit,

    OK.  I would recommend either the digital transmitter to S/PDIF input amplifer, a DAC, or if there is any digital analyzer available for the serial audio data such as an Audio Precision PSIA, that could be used as well.