Media Technology Systems ION8.8 - Manual (Page 12)

Page 12 of 26 Jul‐09
Sine wave 2*F/Sample Rate
Freq OID value 2^31
20 1789570
100 8947849
500 44739243
1000 89478485
10000 894784853
20000 1789569707
Figure 3-6: Frequency OID values
While the sign (sg) and fraction bits (fb) attributes give some indication of how the DSP
might interpret the values (as shown in the examples above), it is the specifics of the
DSP implementation that determine exactly how values are interpreted. The full suite of
crunch values are found in the DSP Conductor folder shown below. DSP conductor can
be downloaded from the Cirrus Logic website.
C:\Program Files\Cirrus Logic\DSPConductor\plugins\coyote\devices
The “imp” xml file contains details of the crunch functions. These can be opened in the
xml editor embedded in Internet Explorer. For example the crunch functions for a sine
wave generator are found in the file “generator_sine_wave.imp.xml”. The file contains
the text for a crunch function written in python, as shown below…
scale_factor = float( property[ "scale_factor" ] )
sample_rate = float( property[ "sample_rate" ] ) * scale_factor
block_size = float( property[ "block_size" ] ) * scale_factor
ramp_time_constant = float( property[ "ramp_time_constant" ] )
block_rate = sample_rate / block_size
ramp = 1 ‐ math.exp( ‐1 / ( ramp_time_constant * block_rate ) )
omega = 2 * frequency / sample_rate;
gain = ‐math.pow( 10, ( level ‐ 20 ) / 20 ) / 16
if mute :
gain = 0
The crunch function can easily be converted to C# or C++ code for use in other
applications.
3.5 OID List for the ION2.0 and ION0.2
The MTS_AMP.xml file on the CDROM has a complete list of all the OID’s and offsets for
the amplifier read/write and red only values, where the devices relate to the schematic
in
Figure 2-1.