The speaker and microphone are controlled through a software API. I learned the programming interface from several EZ-kit sample programs. The sample programs demonstrate all the features needed for the audio tracker.

In addition to software some customized hardware needed to be designed. I built my own microphone pair and amplifier for stereo input. A microphone without amplification would not be able to deliver a strong enough signal for the DSP to process. The connection for the microphones has to be customized to enable the stereo input handled by the EZ-kit.
 

Table of Contents:

• API
• Mic

Programming API [top]

The API to interface to the microphone and speaker enables the SHARC DSP to control the transfer of data from memory to the AD 1881 codec. The codec is responsible for drives the speakers and acquires the signals from the microphones. 

 

The initialization of the API configures which input and outputs are used in the codec. Once initialized, one command is used to transfer the next segment of the audio signal to the codec and simultaneously receive the segment of recorded data. Pointers are maintained to access the transmitted and received audio data. 

The simultaneous transmit and receive command is blocking and in real-time systems considered a critical section. The length of the critical section, however, is optimized to be as short as possible. The DSP accesses memory are parallel; one sequence can read the audio transmitted signal and store the recorded signal. 

It will be interesting to measure the length of the blocking section. The longer the critical section, the more complicated it might become to schedule tasks.

Microphone and amplifier [top]

The microphone amplifier was put together with the help of Nick, Steve, Lea, and John. Nick and Steve gave me a sensitive microphone and circuit of the amplifier. Lea and John helped me find the amplifier. I put the circuit together and verified that it was safe to plug into the EZ-kit without breaking it. Amazingly enough the amplifier worked on the first go.