ARM evaluation board

Evaluation board is designed for evaluation of CORTEX-M3 family microcontroller LPC1343. LPC-Link programator and software LPCXpresso is used for programming and debuging. Board is dedicated for evaluation of these features:

• Bootloader
  
• USB interface
  
• SD card support
  
• I2C interface
  
• SSP interface
  
• UART interface
  
• ADC
  
• LCD
  

Sound recorder
Sound recorder is designed on ARM evaluation board. Real time audio data stream is stored in SD card by standard WAV format. Memory card use FAT32 file system. Sound signal from microphone goes to amplifier and to low-pass filter. After analog signal is converted to digital by internal ADC of the ARM microcontroller. ADC operates at sampling rate 22050Hz and 8bit resolution. It is enough for human voice recording. Status of sound recorder is displayed on LCD. See the photos below:

After recording is stopped - SD card is inserted to PC's card-reader. See the screenshot below how visualy looks the sound waveform:

Digital reverberator
Another application of ARM microcontroller - digital reverberator. Single ADC channel (mono) is used for this purpose. ADC sampling rate - 22050Hz. Maximum resolution (10bit) is used to make sound quality better. The delay of echo is limited by the size of internal LPC1343 RAM memory - 8kB. Such small memory is enough only for storing about 150ms of audio data but it is enough to make echo effect. Delayed sound signal is added to the main signal, so the effect of many delays is generated.
Block diagram of digital reverberator: