32-bit Serial Ports
I am planning a project using an ADAU1452 (and SigmaStudio V4.2).
I intend to use the Serial Ports in their 32-bit mode because I have an FPGA that may add up to 64 channels of 24-bit audio together into a Left/Right mix before feeding it to the DSP chip via a Serial Port running 8 channel TDM.
I have found the note about putting the serial portsinto "Raw 32-bit" mode and running a test program that loops inputs 1 - 8 back out of outputs 1 - 8 seems to be copying the data correctly (just a test of 0x55555555).
Are there any other issues I should be aware of when I start doing audio processing ? Do the core functions work OK even if the signal level goes all the way up to maximum in 8.24 mode ?
I do intend to put a limiter on the final output before attempting to feed it to any 24-bit DAC converters, but I would like to keep the signal uncompressed through the processing chain.
Thanks for any advice
PhilipJ
Audio Signal Processors
adau1452
SigmaDSP Audio Processors
Hello PhillipJ,
No issues.The core is always using all 32 bits so nothing is different once the data is in the core.
The 24 bit converters I assume will be on their own serial port? They really should be so that you can use the built in saturators and truncators that will take care of the sign bit properly when going from 32 bits in the core to 24 bits of the serial ports. When you place it into 32 bit mode it bypasses these functions so do not mic up 32 and 24 bit parts onto the same serial port. Actually, on the input side the setting is for all the channels on each port. So it goes by the port. On the output side you have the option on all the different output cells. Those settings are channel by channel. I don't think I ever check If it really was on an individual channels basis and not the entire port. It is looking like it might be per channel. This would be good if you are sharing a TDM output port between two parts.
If you need to do this I can easily setup a test with a scope and an eval board. Fairly simple test.
Dave T
Hi Dave,
thanks for your reply, great to know.
Thanks for the advice regarding the DACs on their own serial port. The DACs are physically connected to the FPGA that also feeds the input signals so I will either stream an I2S back from the SigmaDSP and pass it directly through the FPGA or, if I need more output streams and run out of ports I can stream the signals back as TDM8 and do some further post processing in the FPGA.
While doing this I discovered that I can "expand" the Output Ports!! I had always wondered why the Input Ports came in from the toolbox as 16/8 channels at a time but the Output Ports came in as individuals. For several years now I have been adding Outputs one at a time and carefully lining them up to make the schematic neat. Never occured to me to right click on the first one and "Grow the Algorithm". :-)
Regards
PhilipJ
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