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BF533 Ez-Kit Lite with audio talkthrough: different output signal levels?

Question asked by SabineF on Sep 26, 2011
Latest reply on Sep 29, 2011 by SabineF



I'm using a ADSP-BF533 EZ-KIT LITE REV 1.1 board and the audio talkthrough example found in \Blackfin\Examples\ADSP-BF533 EZ-KIT Lite\Audio Codec Talkthrough - I2S (C).  In this example the AD1836 is configured via SPI with the following values:

     DAC_CONTROL_1 | 0x000,
     DAC_CONTROL_2 | 0x000,
     DAC_VOLUME_0 | 0x3ff,
     DAC_VOLUME_1 | 0x3ff,
     DAC_VOLUME_2 | 0x3ff,
     DAC_VOLUME_3 | 0x3ff,
     DAC_VOLUME_4 | 0x000,
     DAC_VOLUME_5 | 0x000,
     ADC_CONTROL_1 | 0x000,
     ADC_CONTROL_2 | 0x000,
     ADC_CONTROL_3 | 0x000
The samples received in the receive buffer are simply copied to the transmit buffer resulting in a simple talkthrough.


Running this example with the same input signal (1kHz sine with 2Vpp) connected to Channel0LeftIn and Channel1LeftIn I expect to measure the same output signal on Channel0LeftOut and Channel1LeftOut but I get an amplitude of 1.875Vpp on Channel0 and only 1.422Vpp on Channel1. I get the same result if I use the right channels instead of the left ones.


Where does this effect come from or what do I have to do to get the same output signal levels on channel0 and channel1?


Thanks for your support,