Goals
The primary goal of this project is to program the Altera DE2 board to take audio input encoded with audio frequency-shift keyring (AFSK) and output the corresponding ASCII text over the RS-232 serial port.
Additional goals for this project include:
Encoded audio signal output from serial input
Allow keyboard input for ASCII text
Display incoming and outgoing data on the LCD
Audio Signal
The audio signal is AFSK encoded data in which the data is represented changes in frequency of an audio tone. The higher frequency "mark" tone represents a binary 1, and the lower frequency "space" tone represents a binary 0. The diagram here (from Wikipedia) shows the relationship between the original data and the signal that will serve as input to our system.
For this project, the audio signals will use the following rates:
Data Bit Rate: 1200bps
Space Tone: 1.2kHz
Mark Tone: 2.4kHz
The sound file below is a sample AFSK-encoded message using these specifications. The message reads: KB0MGQ To CQ THIS is a test transmission
| afsk.wav | |
| File Size: | 80 kb |
| File Type: | wav |
