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MSP430F6779: Architecture Advice: MSP430 with External ADC for Multi-Load Power Quality Monitoring

Maryam Dehkordi
Prodigy 91 points
Part Number: MSP430F6779
Other Parts Discussed in Thread: ADS131M08, MSPM0G1506

Tool/software:

I’m designing a 3-phase energy metering and power quality monitoring system (Class 0.2) with harmonic analysis up to the 31st order for a panel board serving 8 three-phase loads (27 channels total: 24 currents + 3 voltages).

Platform Choice
The MSP430 EMDC ecosystem is attractive for calibration, metering routines, and communication. Among supported MCUs for this library, the MSP430F6779 stands out, but its 16-bit internal ADC isn’t sufficient. Therefore, I’m considering the ADS131M08 (24-bit, 17-bit ENOB @16 ksps) for accurate harmonic analysis. The MSP430 would mainly handle system control, calibration, and comms, while the ADS131M08 handles precision sampling.

Key Challenges

  1. Channel Count: ADS131M08 has 8 channels, but I need 27 signals. Options: multiplexing (cheaper but risks time skew/accuracy) vs multiple synchronized ADCs (complex/power/data overhead).

  2. FFT Load: 31st-order harmonic analysis needs 27×512-point FFTs. The MSP430 @25 MHz seems underpowered—likely requiring DSP/FPGA/ARM offload.

  3. Memory Limits: 27 channels × 512 samples (24-bit) = >40 KB just for buffers, exceeding the MSP430’s 32 KB SRAM. FFTs make this worse. Options: external RAM, multiple MCUs, or streamlined processing.

Question
What’s the most practical architecture for this use case? Should I combine MSP430 + external RAM + ADS131M08, or is it better to offload FFT/memory-heavy tasks to a higher-performance MCU/DSP while keeping MSP430 for control/calibration?

  • 0
    TI__Mastermind 29406 points

    Hi Maryam,

    Will loop our experts to give you response soon.

    Thanks!

    Best Regards

    Johnson

  • 0 in reply to Johnson He
    Prodigy 91 points

    Appreciate it, Johnson. Looking forward to it.

  • 0 in reply to Maryam Dehkordi
    TI__Mastermind 25690 points

    Hi Maryam,

    The ADS131M0x is our typical ADC used for CT/Rogowski coil designs for energy measurement, we have the https://www.ti.com/tool/ADS131M08MET-EVM to pair with an MSPM0 product. Our libraries are open source and you can add additional ADS devices if needed, but you may need to lower the sampling speed when adding more ADCs.

    I recommend offloading the FFTs for harmonic calculations because the data amount is quite large to do the amount of FFTs within the window for the new samples.

    The MSP430F677x device is more situated when you do not want the external ADCs as it has internal SD ADCs to do a single-chip solution (the external ADCs will have better performance).

  • 0 in reply to Luke Ledbetter
    Prodigy 91 points

    Luke,
    Appreciate your response.

    This new product of your is very interesting for us. By the way, if I want to use 4 ADCs (ADS131M08) with this core (MSPM0), while using another CPU (ARM cortex M7 for harmonics and FFT calculations), how can I stay with 8KHz sampling rate? Solution to this challenge is very important to us and I would appreciate your idea on this matter.  

    I also have another question. What type of CT you recommend for 100A primary current maximum, and frequency range of 45 Hz to 20 KHz, to be able for having harmonics up to 63th order.

    Regards,

    Maryam

  • 0 in reply to Luke Ledbetter
    Prodigy 91 points

    Luke,
    Thanks for the response.

    To maintain a high sampling frequency of the ADS131M0x with 4 ADCs, would you recommend using an ARM Cortex-M7 to receive the raw ADC data and then transfer it to an MSPM0 MCU for fundamental energy metering parameter calculations, while the Cortex-M7 itself handles harmonic calculations?

    I would appreciate it if you could share your thoughts on this.

  • 0 in reply to Johnson He
    Prodigy 91 points

    John,

    Please be kindly aware that I am still waiting for your response, to the follwoing discussion!

    Thanks,
    Maryam

  • 0 in reply to Luke Ledbetter
    Prodigy 91 points

    Please be kindly aware that I am still waiting for your response.

    Thanks,
    Maryam

  • 0 in reply to Maryam Dehkordi
    TI__Mastermind 25690 points

    Hi Maryam,

    We haven't done a use case with essentially 24 power calculations on our M0 devices yet. Although you share 3 voltages so the VRMS doesn't need to be duplicated the amount of data might be too great for a single M0 class device.

    I definitely recommend a higher level processor to do the FFTs, but you can use our M0 class devices and break down the use cases into 4 separate M0 devices. The MSPM0G1506 with the math accelerator and 80Mhz would be my recommended device to do the energy metrology power calculations (minus harmonics). We have our energy metrology library that is open so you can adjust some functions and you might  be able to remove some code and fit this into fewer devices.

    3-phase code below 

    https://dev.ti.com/tirex/explore/node?node=A__AFNBBM0ry6HfZ9WtK0DJtQ__MSPM0-SDK__a3PaaoK__LATEST

    I am going to pass this thread to our processors team to help investigate a good main processor for the application.

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