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Original question:

TMS570LC4357: Halcogen example_epwm_adc.c

TMS570LC4357: How to test and verify the ADC converted data which is triggered by ETPWM?

Bharath_R
Prodigy 100 points
Part Number: TMS570LC4357

Hi,

I'm using TMS570LC4357 HDK,

and I'm testing ADC1 channel 0 hardware trigger using EVENT group and trigger source is EPWM_EVENT_B.

Every time interrupt occur handler will get call and converted data will be around 2667(slightly difference)  always, even though for other channels which are connected to EPWM.

if i change the duty cycle to 0, then the connected channel's ADC value will change to 0.

why other channels ADC value is 2667. and how to verify?

Thanks and Regards,

Bharath

  • 0
    TI__Guru**** 196156 points

    Hello Bharath,

    Your question: ADIN[0] is connected to external input, and other ADC channels are left unconnected (floating). But the unconnected ADC channels get the same sampled value as ADC channel 0. 

    The sampled value of a floating ADC channel is indeterminate. If you connect those unused ADC pins to GND, what are the sampled value for those channels? Please try to enable the sample capacitor discharge mode. This mode will discharge the sampling capacitor before starting the sampling phase of the next channel.

  • 0 in reply to QJ Wang
    Prodigy 100 points

    Thank you Wang,

    after enabling sample capacitor discharge mode unconnected channel values are below 100.