From the menu options, select one of the available demonstration programs to run on the EZ-KIT Lite.
• DTMF…
Selects the DTMF DSP demo program. This demonstration generates Dual-Tone Multi-Frequency (DTMF) tones, as used in the telephone network for push-button signaling. A DTMF tone is composed of two different single frequency tones - one of four row tones added to one of four column tones. Thus, a full implementation of a DTMF standard tone generator can generate 16 different tones (only 12 are commonly used on consumer handsets).
When selected the Windows Application Interface will download the necessary DSP program to the EZ-KIT LITE resulting in a dialog box.
When it outputs a DTMF tone, EZ-KIT generates the two requisite sine waves, scales them and adds them, and then outputs the result to the codec for conversion to an analog signal. At the start of this program, EZ-KIT generates a dial tone to the output speaker. The following selections are possible.
- Generate dial tone
This selection may be selected by clicking the corresponding radio button or typing the letter ‘t.’ A standard dial tone which is a sum of continuous sine waves is generated.
- Generate DTMF digits
This option may be selected by clicking the corresponding radio button or typing the letter ‘d.’ The phone number of an Analog Devices DSP applications engineer is programmed into the demo program. Make this selection to generate the phone number. If you hold an off-hook telephone handset to the output speaker, the DTMF tones will tell the network call switching apparatus to connect you to the applications engineer. Do this only if you want to make a call.
- Close
This option terminates the demonstration program and restores the EZ-KIT resident monitor program before returning the user to the top menu bar selection. This allows a new demonstration to be selected.
• Filtering…
Selects the FIR Filtering DSP demo program. This program demonstrates the effect of four bandpass filters against no filter on microphone input or an internally generated noise source.
When selected the Windows Application Interface will download the necessary DSP program to the EZ-KIT Lite and display a dialog box.
This demonstration starts with a talk-through program. The AD1847 codec digitizes the analog microphone input and transmits the data to the DSP’s serial port. The DSP reads data from the serial port and retransmits the data back to the codec. The codec converts the data to an analog signal that drives the speaker. No digital processing is performed on the data. When you speak into the microphone, you should hear your voice through the speaker.
The top row radio buttons use voice input from the microphone.
The filters have equivalent bandwidth and are evenly spaced on a logarithmic frequency axis. All FIR filters are 256 taps, and have been designed for 0.1 ripple.
stop band pass band stop band
1 0 - 269 328 - 448 547 - 4000
2 0 - 426 521 - 710 866 - 4000
3 0 - 675 825 - 1125 1375 - 4000
4 0 - 1070 1308 - 1783 2179 - 4000
The bottom rows radio buttons use random noise as inputs.
- Close
This option terminates the demonstration program and restores the EZ-KIT resident monitor program before returning the user to the top menu bar selection. This allows a new demonstration to be selected.
• Echo Cancellation…
Selects the Echo Canceller DSP demo program. This program demonstrates echo cancellation on a simulated echoing channel.
The AD1847 codec digitizes the analog microphone input and transmits the data to the DSP’s serial port. The DSP internally generates an echoed signal by summing the serial input with the output of a simulated echo channel. The echo channel consists of a linear delay implemented as a long FIR filter with zero-value tap weights and a 16-tap dispersive FIR filter. The echo canceled output is sent to the codec for reconstruction.
When selected the Windows Application Interface will download the necessary DSP program to the EZ-KIT Lite resulting in a dialog box.
Initially the program sends the echoed output to the codec without echo cancellation. The following selections are possible.
- Next
When this button is depressed for the first time the program enters echo cancellation mode. There will be a significant reduction in echo. Further depression of the button will change the position of the dispersive filter and will force the filter to adapt to a new echo path.
- Close
This option terminates the demonstration program and restores the EZ-KIT resident monitor program before returning the user to the top menu bar selection. This allows a new demonstration to be selected.
• ADPCM…
Selects the ADPCM DSP demo program. This program demonstrates Adaptive Differential Pulse Code Modulation (ADPCM) capabilities. ADPCM consists of a number of real-time speech compression algorithms. For each sampling period it employs a linear predictive filter to generate a predicted output. The difference between the predicted output and actual sampled value is sent through the communication channel. Since the dynamic range of the differential error is significantly lower than the dynamic range of the voice signal, a lower bit rate results.
When selected the Windows Application Interface will download the necessary DSP program to the EZ-KIT Lite resulting in a dialog box.
Initially the digitized microphone samples from the codec are sent directly to the codec for reconstruction. The following selections are possible.
- ADPCM coding
This option enables the ADPCM encoding/decoding feature. Each digitized microphone sample from the codec is first encoded and then decoded using ADPCM. After it is decoded, it is sent back to the codec for reconstruction. The red LED will light up when ADPCM encoding is in effect.
- Straight through
This option enables the straight through. The digitized microphone samples from the codec are sent directly back to the codec for reconstruction. The red LED will be off when straight through is in effect.
- Close
This option terminates the demonstration program and restores the EZ-KIT resident monitor program before returning the user to the top menu bar selection. This allows a new demonstration to be selected.
• 7.8 kbs LPC…
Selects the 7.8k LPC DSP demo program.
- Interrupt button on EZ-KIT Lite
Push the Interrupt button on EZ-KIT Lite to toggle between talk through and 7.8k LPC encoding. The red LED will light up when LPC encoding is in effect.
- Close
This option terminates the demonstration program and restores the EZ-KIT resident monitor program before returning the user to the top menu bar selection. This allows new a demonstration to be selected.
• 2.4 kbs LPC…
Selects the 2.4k LPC DSP demo program.
- Interrupt button on EZ-KIT Lite
Push the Interrupt button on EZ-KIT Lite to toggle between talk through and 2.4k LPC encoding. The red LED will light up when LPC encoding is in effect.
- Close
This option terminates the demonstration program and restores the EZ-KIT resident monitor program before returning the user to the top menu bar selection. This allows a new demonstration to be selected.
