User Manual
XScopes
User’s Manual
DS-XScopes-3.5 – December, 2014 Page | 27
4.1 Predefined Waveforms
Table 8: AWG Preprogrammed Waveforms
The XScope can output the following waveforms: Sine, Square, Triangle and Exponential. There is a “Periodic Noise”
option that fills the AWG buffer with random data, it is periodic because the same data is output over and over, but each
time the Noise wave is selected, new random data will be generated. There is also a custom waveform which is initially set
with an ECG wave, but can be changed with the PC interface (see section 5.2).
4.2 Parameter Sweep
The XScope has a SWEEP feature, which increases one or more parameter values automatically on each screen refresh
of the oscilloscope. When the sweep is enabled, three dots will appear at the bottom of the screen, representing the start,
end, and current sweep value. When doing a Frequency sweep, the frequency range is determined by the current time
base. Since the frequency sweep is synchronized with the oscilloscope, displaying perfect frequency plots is easy. To make
a frequency plot, set the mode to FFT, and set the display to persistent. See section 8.6 for an example.
4.2.1 Sweep Modes
In the Sweep Mode menu, the sweep direction can be changed. Automatic change of the direction is done by enabling
the Ping Pong mode. The sweep acceleration increases or decreases the sweep speed, the sweep speed is reset when
reaching the start or end of the sweep.
4.3 Technical Details
The waveform is stored in a 256 byte long buffer, this buffer is fed to the XMEGA's DAC thru the DMA. Once the
waveform is set, the waveform will be generated without any CPU intervention. The maximum conversion rate of the DAC
is 1Msps, this limits the maximum output frequency of the AWG as a system. For example, if the AWG is generating a
sinewave with 256 points, the maximum frequency is 3906.25Hz. If generating a sinewave with only 32 points, the
maximum frequency is 31.25KHz. The AWG amplifier has a low pass filter of 44.1KHz. The predefined AWG Frequency
range is: 1Hz thru 125 kHz
The resolution of the waveform generator varies depending on the frequency range: the lower the frequency, the higher
the resolution. Note that the possible frequencies are discrete:
Cycles: Integer number, with these possible values: 1, 2, 4, 8, 16, 32
Period: Integer number, with values between 32 and 65535
Sine Wave
Square Wave
Triangle Wave
Exponential
Periodic Noise
Custom Wave *