Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

  • State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 78 subscribers
  • Views 111 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

MSP430i2040: Interfacing EMDC with another MCU over UART

MSP430I2040: Calculations done by EMDC PC software

manish
Prodigy 60 points
Part Number: MSP430I2040

Tool/software:

I am using the EMDC software to generate code for i2041. The configuration has one voltage channel and one current channel with CT.

Unfortunately, we could not get the HID to work with 5529LP. The green LED never blinks on 5529LP even after programming the TXT file many times. We can not long put more effort on that as we need to get the rest of the system working.

So, we are going through the UART protocol on i2041 and interface to a host MCU. Since the EMDC GUI is not present, we see values around 6000 decimal in gEmSWResult.phaseResults[phaseIdx].VRMS variable. The input voltage is 230V AC at 50Hz with voltage divider with 1.8k and 2M resistor.

Question:

1. Is the EMDC GUI converting the ADC sample values to the actual values - as in, 6000/32767 * 1.2 * 2000 / 1.8 = 244 Vrms? Here, 1.2 is Vref.

2. If the EMDC is not converting the ADC values to the actual values, then is this a part of the "calibration" commands where the voltage divider, and current shunt related scaling factors are programmed into i2041?

3. Whether #1 or #2, it seems we have to do the same on the host MCU in our system - right? Is there a way to do this math in the i2041 metrology MCU itself?

Please advise. Thanks.

  • 0
    Prodigy 60 points

    One followup: if we see a Vrms reading of 6216, it calculates to about 253Vrms, against the reading of 245V with a calibrated lab instrument. How should we go about fixing this error? Please suggest. Thanks.

  • 0 in reply to manish
    TI__Expert 7792 points

    Hi, 

    There are many factors that affect the results in the signal chain.

    Such as For example, the resistor 1.8k and 2M's accuracy.

    manish said:
    One followup: if we see a Vrms reading of 6216, it calculates to about 253Vrms, against the reading of 245V with a calibrated lab instrument. How should we go about fixing this error? Please suggest. Thanks.

    Need to confirm that whether this is a linearity or gain error.

    And during the production, maybe a factory calibration is need.

    Regards,

    Helic

**Attention** This is a public forum