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Intefacing CM-BF537 to the AD1836

Question asked by MTG on Oct 17, 2011
Latest reply on Jan 28, 2013 by Prashant



I have an EVAL-BF5xx Board v4.0 with a CM-BF537E, and I want to interface it to the AD1836 multichannel codec.


I am using the EXT-BF5xx-Audio C Based AD1836 talkthorugh example. In this example audio samples received from the AD1836 are moved into the DSP's receive buffer, using DMA.  The samples are processed by the ADSP-BF5xx and place in the transmit buffer. The transmit buffer is used to transmit data to the AD1836.  This results in a simple talk-through where data is moved in and out of the DSP without performing any computations on the data.


However, when I listen to the output channel, it sounds quietly, with a very low volume. Furthermore, when plotting "iChannel0LeftIn" (the signal that comes from the input receive buffer "iRxBuffer1"), I can see that it is not centered in 0. It has a big negative DC offset.


I don't know why is this happenning. I have the AD1836 configured with 16 bits data word length and 48 kHz sample rate. I copy the array for registers to configure the ad1836:


volatile short sCodec1836TxRegs[CODEC_1836_REGS_LENGTH] =
                    DAC_CONTROL_1    | 0x010,
                    DAC_CONTROL_2    | 0x000,
                    DAC_VOLUME_0    | 0x3ff,
                    DAC_VOLUME_1    | 0x3ff,
                    DAC_VOLUME_2    | 0x3ff,
                    DAC_VOLUME_3    | 0x3ff,
                    DAC_VOLUME_4    | 0x3ff,
                    DAC_VOLUME_5    | 0x3ff,
                    ADC_CONTROL_1    | 0x000,
                    ADC_CONTROL_2    | 0x1a0,
                    ADC_CONTROL_3    | 0x000                                                   


Thanks a lot.