CALCRATIO

Table of Contents

• Introduction
• System Flow Overview
• Supported Combinations
• Steps to Run the Example
• See Also
• Sample Output

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

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

CALCRATIO

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
...