Developing Sigma DSP Cluster

Hello Jean,

The SigmaDSP forum has officially opened so I am able to answer your questions now.

a) Is it possible to wire the Audio Input Codec (as master) on 6 DSP without glue logic ?

Yes. The evaluation board you are using should be set up in this way already. Check the schematics for more details.

b) And about the Master Clock ? Usually I use a hibrid square wave clock up to 3 chips. What glue logic is really necessary to

this project ?

I would suggest using the AD1939's clock generator with a crystal to generate master clocks for the entire system. You will need some sort of buffer, however, because the MCLKO/XO pin lacks the drive strength to drive other ICs. Make sure that the buffer's fanout meets your requirements for this system.

c) Is it possible to draw the board just using 2 layers ?

It certainly is possible, but will make your design more susceptible to noise and will probably decrease its audio performance.

d) I need to put audio compressor on all inputs and I saw that the curve has 32 points, but I dont know how to map an HMI user interface

to control all points of this block. My boss suggest me annotate several curves and list them to user choose (its a simple manner but ....)

The compressor table actually has 33 points. The easiest solution is to create some example curves and save the table data as presets. You could also derive the table point calculations for a simple threshold/ratio compressor and include those in your system controller, which would give you greater flexibility.

The SigmaStudio software engineers are currently developing a more traditional compressor interface that has a user interface similar to that of pro audio equipment: threshold, ratio, attack, decay...

e) If I use the TDM channel (to simplify design) what the maximum sampling rate (I suppose that is 48 Khz).

Table 36 of the AD1940 datasheet (Rev. A) shows the options for TDM modes.  I've attached a copy for your reference. If the AD1940 is a slave, then all sample rates (48, 96, and 192 kHz) are possible with TDM8 and TDM16 modes.

f) I will develop the controller firmware using C (ARM7). Does anyone has an SDK to control the IC's 1940 and 1939 (using SPI) ?

SigmaStudio includes tools for generating code and header files for microcontrollers. After compiling your project, click the "Export System Files" button on the toolbar to generate these output files.

Hello Jean,

The SigmaDSP forum has officially opened so I am able to answer your questions now.

a) Is it possible to wire the Audio Input Codec (as master) on 6 DSP without glue logic ?

Yes. The evaluation board you are using should be set up in this way already. Check the schematics for more details.

b) And about the Master Clock ? Usually I use a hibrid square wave clock up to 3 chips. What glue logic is really necessary to

this project ?

I would suggest using the AD1939's clock generator with a crystal to generate master clocks for the entire system. You will need some sort of buffer, however, because the MCLKO/XO pin lacks the drive strength to drive other ICs. Make sure that the buffer's fanout meets your requirements for this system.

c) Is it possible to draw the board just using 2 layers ?

It certainly is possible, but will make your design more susceptible to noise and will probably decrease its audio performance.

d) I need to put audio compressor on all inputs and I saw that the curve has 32 points, but I dont know how to map an HMI user interface

to control all points of this block. My boss suggest me annotate several curves and list them to user choose (its a simple manner but ....)

The compressor table actually has 33 points. The easiest solution is to create some example curves and save the table data as presets. You could also derive the table point calculations for a simple threshold/ratio compressor and include those in your system controller, which would give you greater flexibility.

The SigmaStudio software engineers are currently developing a more traditional compressor interface that has a user interface similar to that of pro audio equipment: threshold, ratio, attack, decay...

e) If I use the TDM channel (to simplify design) what the maximum sampling rate (I suppose that is 48 Khz).

Table 36 of the AD1940 datasheet (Rev. A) shows the options for TDM modes.  I've attached a copy for your reference. If the AD1940 is a slave, then all sample rates (48, 96, and 192 kHz) are possible with TDM8 and TDM16 modes.

f) I will develop the controller firmware using C (ARM7). Does anyone has an SDK to control the IC's 1940 and 1939 (using SPI) ?

SigmaStudio includes tools for generating code and header files for microcontrollers. After compiling your project, click the "Export System Files" button on the toolbar to generate these output files.