We get noise listening to the analog output from the ssm2603 when sending a signal with a low amplitude from the Blackfin on a rev 1.1 ADZS-BF526-EZBRD. The noise sounds like a tone or filter sweep and seems to be directly related to the absolute amplitude of the signal.
Attached is a slightly modified version of Analog's 'loopback' project.
For a sound-demo of the issue, check the demo video attached.
The source is modified to output either a square or a sine, controlled by this define
The signal is lowered in volume either in discrete steps by shifting it down or scaling with a multiplier. Select method with:
Otherways I'm using all the default settings from Analogs loopback example, except for SSM2603_WLEN_32 for 32 bit word length.
Note as the signal will be quite low in volume from the EZ-board needs to be powered from the battery and the programmer should be disconnected.
Has anybody else experienced this noise? Have I made some obvious mistake?
My gut feel is that there is some mismatch in the setup of the I2S communication.
Any input greatly appreciated.