Audio Field Recorder System Software Design

Audio Field Recorder System Software Design Western Washington University Kent sykes 2009

General System Design • MCU-Freescale MCF51QE128 • 50.33 MHz Bus Frequency • On-Chip Resources • 128 kB Flash • 8 kB RAM • Memory Requirements • 40 kb Flash • 6 kB RAM • Timeslice Kernel • 22.675 μs Timeslice

Kernel Task Design • Startup Task • System Task • Key Task • LCD Task • AudioData Task • Codec Task

Startup Task • Initialize system • Period (max) • Only run once • Execution Time (max) • ~100ms

System Task • Provides user interface • Calls LCD functions • Determines system state • Uses EFSL (embedded file systems library) to navigate files on the SD card • Execution time (max) • 30μs • Period (max) • 100ms

Key Task • Scans for key press • Execution Time (max) • 2.2 μs • Period (max) • 10ms

LCD Task • Writes information to LCD display • Execution Time (max) • 2.5ms • Period (max) • 100ms

AudioData Task • Loads or stores audio data from the SD card using the EFSL Library • Maintains audio sample buffer • Execution Time (max) • 4ms • Period (max) • 5.8ms

Codec Task • Control Codec function via IIC • Get audio samples from the audio buffer in playback via modified SPI • Send audio samples to the audio buffer in record mode via modified SPI • Execution Time (max) • 6 μs • Period (max) • 22.68 μs

CPU Load

Modules

Audio Field Recorder System Software Design