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ADS127L11: How to translate 2s-complement output code of ADS127L11 into PCM format?

John11513
Expert 5720 points

Part Number: ADS127L11

Hi,

My customer's old design is using audio ADC for signal sampling. I want to convince them replace audio ADC with ADS127L11. Considering the Audio ADC output is PCM code while ADS127L11 is 2s-complement code. I am wondered how to translate the output of ADS127L11 into PCM code to adapt this new ADC with their old system?

Thank you!

John

  • 0
    TI__Guru 64795 points

    Hello,

    Good suggestion, we often see customers using high performance ADCs in audio applications for higher performing systems.  Would you confirm which Audio Serial Interface (ASI) PCM mode of operation you're interesting in mapping to?  Are you using I2S, LJ, RJ, TDM?  

    The popular I2S ASI formatted data is transmitted as a binary two's complement output, similar to the output format from the ADS127L11.  The SPI interface is quite different than the ASI interface and the main requirement will be for the customer to write the driver such that the ADS127L11 SPI interface is being read from at a consistent sampling rate (e.g. 48kHz) while also packetizing/converting the output to the desired 16/24/32-bit ASI data on either the left (L) or right (R) slot in the audio bus at the desired sampling rate.  If the ADS127L11 sampling rate doesn't match the output sampling rates, then some form of sample-rate conversion (SRC) may be required.