CALCRATIO

Introduction

This example demonstrates real-time clock-ratio estimation between two asynchronous audio clocks (e.g., a 32 kHz receiver and a 48 kHz transmitter). The estimated ratio is periodically updated and fed to the SW ASRC (Software Asynchronous Sample-Rate Converter) so that the receiver can resample the incoming stream without clicks or drift.

Every 0.5 s a timer tick triggers the capture of:

  • Rx Sample Counter — number of samples consumed by the MCASP-Rx (32 kHz domain)

  • Tx Sample Counter — number of samples produced by the MCASP-Tx (48 kHz domain)

  • MCASP is configured in 32 bit data format

Note

  • This demo does not perform actual audio streaming or sample-rate conversion.

  • Ensure that the McASP RX and TX DMA configurations use the same DMA transfer size, including the loop-job buffer.

System Flow Overview

../../_images/calcratio.png

CalcRatio DMA Counter Flow Overview

Supported Combinations

Parameter

Value

CPU + OS

c75ss0-0 freertos

Toolchain

ti-c7000

Board

am62dx-evm

Example folder

examples/signal_processing/calcratio

Steps to Run the Example

  • When using CCS projects to build, import the CCS project for the required combination and build it using the CCS project menu (see Using SDK with CCS Projects).

  • When using makefiles to build, note the required combination and build using make command (see Using SDK with Makefiles)

  • Connect audio devices as mentioned in the introduction

  • Launch a CCS debug session and run the executable, see CCS Launch, Load and Run

See Also

Signal Processing

Sample Output

Shown below is a sample output from the script when the application is run,

Calcratio + DMA Couter playback example started.
ActualRatio for 32000Hz to 48000Hz = 1.500000
ActualRatio for 32000Hz to 48000Hz = 1.500492
ActualRatio for 32000Hz to 48000Hz = 1.500246
ActualRatio for 32000Hz to 48000Hz = 1.500328
ActualRatio for 32000Hz to 48000Hz = 1.500246
ActualRatio for 32000Hz to 48000Hz = 1.500295
ActualRatio for 32000Hz to 48000Hz = 1.500246
ActualRatio for 32000Hz to 48000Hz = 1.500281
ActualRatio for 32000Hz to 48000Hz = 1.500246
...