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Original question:

LAUNCHXL-F28379D: Creating a booloader for F28379D (testing with LAUNCXL-F28379D)

TMS320F28379D: The usage issue of ADC

WMWMS
Prodigy 80 points

Part Number: TMS320F28379D
Other Parts Discussed in Thread: LAUNCHXL-F28379D, C2000WARE, ADS8586S

Hi,everyone! 

1.In LAUNCHXL-F28379D, when I sample the current sensor with the ADC, the measured results always have significant abnormal interference (out of a hundred points sampled, there will be one point with an error of nearly 0.045V). Could it be a problem with my software configuration? The voltage data of the AD interface was measured with other precision instruments. (The measured current value was normal, which can prove that the voltage signal of the current sensor is fine. )

2. If I want to use an off-chip ADC to reduce interference, could you recommend a solution for me? Here are my work requirements:

 a) I need to collect 5 current data points.

 b) My interrupt time is 10kHz. To leave some running time for other algorithms, the communication time between the off-chip ADC and dsp needs to be within 50 seconds. 

Thank you for taking the time and effort to watch this issue!

  • 0
    TI__Expert 3070 points

    Hi,

    Your ADC interference issue showing occasional 0.045V errors is likely related to software configuration rather than hardware, given that your external measurements confirm the sensor signal is clean. Several configuration aspects should be investigated:

    Clock Configuration When using C2000Ware examples, ensure the correct on-board clocking circuit is configured by adding "_LAUNCHXL_F28379D" as a predefined symbol in your project properties. Incorrect clock configuration can cause timing issues that manifest as intermittent ADC errors.
    ADC Signaling Mode The F2837xD ADC supports both single-ended and differential signaling modes. A key benefit of using differential signaling mode is its ability to cancel noise that may be introduced common to both inputs. If you're currently using single-ended mode where only a single pin (ADCINx) is sampled, switching to differential mode could significantly reduce the interference you're experiencing.
    ADC Triggering Configuration The ADC triggering and conversion sequencing are managed by Start-of-Conversion (SOCx) configuration registers controlled by software. These registers specify the trigger source, channel to convert, and acquisition sample window duration. Verify that your trigger sources (General-Purpose Timers, ePWM modules, external pin, or software triggers)  are properly synchronized with your 10kHz interrupt rate.

    For your requirements of 5 current data points at 10kHz interrupt rate with <50μs communication time, I recommend the following solutions:

    Top Recommendation: ADS8586S
    The ADS8586S is the optimal choice for your application:
    • Channels: 6 simultaneous-sampling channels (exceeds your 5-channel requirement)
    • Resolution: 16-bit for excellent current sensing accuracy
    • Speed: 200kSPS per channel, easily meeting your 10kHz interrupt rate 
    • Communication Time: ~4μs for 5 channels at 20MHz SPI, well within your 50μs requirement
    • Key Advantage: Simultaneous sampling means all channels are sampled at the same instant, which is critical for reducing interference and ensuring accurate multi-phase current measurements
    • Interface: SPI compatible with your F28379D DSP 

    Alternative: ADS8555

    The ADS8555 offers higher performance at lower cost:
    • Channels: 6 simultaneous-sampling channels 
    • Resolution: 16-bit
    • Speed: 630kSPS per channel, providing higher bandwidth than ADS8586S
    • Communication Time: ~3μs for 5 channels via SPI
    • Interface: SPI plus parallel options for flexibility