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DE2-70 User Manual
82
Figure 6.14. Software Stack of the SD music player demonstration.
The audio chip should be configured before sending audio signal to the audio chip. The main
program uses I2C protocol to configure the audio chip working in master mode, the audio interface
as I2S with 16-bits per channel, and sampling rate according to the wave file content. In audio
playing loop, the main program reads 512-byte audio data from the SD card, and then writes the
data to DAC FIFO in the Audio Controller. Before writing the data to the FIFO, the program have
to make sure the FIFO is not full. The design also mixes the audio signal from the microphone-in
and line-in for the Karaoke-style effects by enabling the BYPASS and SITETONE functions in the
audio chip.
Finally, users can obtain the status of the SD music player from the 2x16-LCD module, the 7
segment display and the LEDs. The top and bottom row of the LCD module will display the file
name of the music that is playing on the DE2-70 board and the value of music volume, respectively.
The 7 segments display will show how long the music file has been played. The LED will indicate
the audio signal strength.
Demonstration Setup, File Locations, and Instructions
• Project directory: DE2_70_SD_Card_Audio_Player
• Bit stream used: DE2_70_SD_Card_Audio_Player.sof
• Nios II Workspace: DE2_70_SD_Card_Audio_Player\Software
• Format your SD card into FAT 1 6 format
• Put the played wave files to the root directory of the SD card. The provided wave files must
have a sample rate of either 96K, 48K, 44.1K, 32K, or 8K. Besides, the wave files must be
stereo and 16 bits per channel. Also, the file name must be short filename.
• Load the bitstream into the FPGA on the DE2-70 board.
• Run the Nios II IDE under the workspace DE2_70_SD_Card_Audio_Playe\Software
• Connect a headset or speaker to the DE2-70 board and you should be able to hear the music
played from the SD Card