GEX demo measuring the amplitude and phase frequency response of analog filters
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# demo-bode-plotter
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GEX demo measuring the amplitude and phase frequency response of analog filtes.
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This demo uses an external waveform generador AD9833 (on a breakout module from eBay).
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It could also use the built-in DAC, but the performance is sub-optimal and the plots
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obtained with it had a lot of glitches. Feel free to adjust the script to use the
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internal DAC and try it.
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The AD9833 is connected to SPI on pins PA4 (SS), PA5 (SCK), and PA7 (MOSI).
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Pins PA1 and PA2 are used by the ADC and attach before and after the filter (DUT).
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The generator has low output levels (0.65 V max). To better utilize the
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input range of the ADC, I used OP213 in a non-inverting configuration
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(resistors 7.5k and 2.2k), with a 10M resistor from the input to GND. This gives us gain
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of around 4.4, enough to reach just under 3V.
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## To run the script
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- Ensure you used `git clone --recursive`, or use `git submodule init`, `git submodule update`
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- Load the attached UNITS.INI file into GEX (it is intended for GEX Hub)
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- Connect the external circuitry and run the script.
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Dependencies - pyplot, numpy, and whatever you need to use the GEX library: typically pyusb or pyserial.
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## Example outputs
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