SpinCore PulseBlasterDDSII
LabVIEW Extensions
PBLV_DDSII_amp_test.vi
This PBLV-DDS-II Amplitude Example VI outputs a sine wave with DDS0, cycling
through 4 different amplitudes which are set in the amplitude registers. It also outputs a
sine wave with DDS1, cycling through the same 4 amplitudes but in reverse order.
To start the VI press the Run button at the top of the LabVIEW window (for stand-
alone programs, the program is run automatically when opened). First you must insert the
clock frequency value of the board into the “clock_freq (MHz)” field as well as the path to
spinapi.dll as described above. Next, the appropriate frequency, phase, and amplitude
registers must be set. Both DDS cores initially have these values for their registers:
amplitude registers 0, 1, 2, and 3 are set to .25, .5, .75, and .99 respectively (this signifies
25%, 50%, 75% and 99% amplitude), frequency register 0 is set to 1 MHz, and amplitude
register 0 is set to 1. *Note that due to an unknown issue in some boards, if the amplitude
is set to 1 (100%) the output waveform is inverted.* Next the instructions must be set up
appropriately. This VI programs the PBDDS-II board with 6 instructions. The first
instruction resets the phase and the RF output is disabled for both DDS cores. The next
four instructions enable output for 2 μs and use amplitude register 0, 1, 2, and 3
respectively for DDS0, and amplitude register 3, 2, 1, and 0 respectively for DDS1. All
instructions use frequency register 0 and phase register 0. The last instruction disables the
output for 1 ms to allow for oscilloscope triggering. You may change these instructions and
registers as desired.
When the instructions and registers are set up correctly, you must first load the
board by clicking the “LOAD BOARD” button and then wait until the button becomes
inactive. To start the program click on the “START” button, and to stop the program click
on the “STOP” button. If there are multiple boards connected to your computer, the
“CHANGE BOARD” button will change the board that is being programmed to the one
specified by the “board_num” field. All four functions are independent and may be run at
any time, however an instruction sequence must be loaded into the board before it can be
started.
Caution
: After pressing STOP, all digital output bits may maintain their final state.
The RF output will return to 0V when the stop button is pressed.
See Figure 11 for a screen shot of the PBLV-DDSII Phase Test.
22
2011-04-29
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