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Using Sigma-Delta (SDFM) to measure analog signal for F28379D

Hello,

I would like to measure analog input signal (+/-250mV) by the external modulator AMC1304 and be able to display filtered SDFM output bit stream in EMBED. I was able to configure ePWM5A/ePWM5B to generate 50% duty clock 20MHz distributed to AMC1304 (pin 13) and SD Filter Module Channel 3 at F28379D (SD3-CLK). Scoping CLK line shows that PWM works fine and Data line also outputs bit stream. The problem is that EMBED SDFM block outputs nothing.

Could you guide me how configure correctly ePWM and SDFM blocks? Could you share any example of Sigma-Delta measurement in VisSim model?

Attached are my blocks configuration.

Thank you,

Marcin

ePWM5A_for_Sigma-Delta_CLK.png

SDFM_channel_3.png

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v2021.2

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pete darnell_21649

Hi Marcin,

Can you attach the diagram you are using to test?

Thanks,

Pete

Marcin Jelen

Hi Pete,

Attached please find the SDFM test diagram. The purpose was to figure out on the Plot or Display what is the SDFM block output, as not mentioned in Help and how to decode this information in acc. with input voltage to ext. modulator AMC1304.

I experience as well strange behavior of SDFM block during its properties configuration.

The selections from drop-down lists or check box value or numerical field values are not always acknowledge with OK button. When SDFM block re-opened to verify they are unchanged or not all previously set values are saved. I need to repeat configuration over and over again until it is finally saved as desired.

Curious is also the fact that CPU F28379D I use has built-in two SDFM units, however SDFM block Unit property is grayed out with Unit=1 (no selection possible).