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TMS320F28377D: Regarding change from existing EMIF method to SPI communication method

ysgeum
Prodigy 20 points

Part Number: TMS320F28377D

Dear,
I would like to review changing the ADC and DAC reception values from the EMIF method to the SPI communication method when controlling the existing motor as shown below.
I would like to inquire whether it is possible to change to the SPI communication method and whether there will be any problems.

MCU: TMS320F28377DPTPS
S/W control: FOC vector control through PMSM and resolver sensor

MCU timing 
- Current PI control loop: 100us (10kHz) 
- Speed PI control and communication loop: 2ms (500Hz) 

- Current command reading cycle: 100us (10kHz) 
- Speed command reading cycle: 100us (10kHz) 

- Speed Feedback Cycle: 100us (10kHz) 
- Current Feedback Period: 100us (10kHz) 
- Position Feedback Period: 100us (10kHz)

1. Existing method (reading ADC and DAC data for commands and feedback using EMIF method) 
ADC: AD7656BSTZ-1 
DAC: DAC8728SPAG

2. Change review method (reading ADC and DAC data for commands and feedback through SPI communication) 
ADC: ADS8684AIDBT 
DAC: DAC81404RHBT

Will there be any problems with motor operation, MCU load, reliability, etc. if changed as above?
Thank you.

  • 0
    TI__Intellectual 2786 points

    Hi Ysgeum, 

    From the board's perspective both these modules can be configured via SPI. Is your concern regarding the external modules itself or the working of SPI on TMS320F28377DPTPS?

    Regards,
    Pranav Siddappa

  • 0 in reply to Pranav Siddappa
    Prodigy 20 points

    Thanks for your reply.

    It is the working of SPI on TMS320F28377DPTPS.

    Currently, all work is being done within the 100us timer of TMS320F28377DPTPS.
    (Receives analog commands from ADC through EMIF interface,
    Performs motor FOC vector control,
    DAC exports analog results to EMIF interface)

    However, I am concerned that if it is changed to SPI communication instead of EMIF, there will be problems with operation within the 100us timer.

    If you configure a separate timer and implement SPI communication within the timer, I think there will be problems with motor operation due to lack of synchronization.

    However, using DMA or dual core is likely to be difficult due to the complexity of the S/W, development period, reliability verification period, etc.

  • 0 in reply to ysgeum
    TI__Intellectual 2786 points

    Hi Ysgeum, 

    The SPI on TMS320F28377DPTPS can run up to 50MHz and be configured for a variety of 125 different baud rates and four different clock schemes    .
    This speed is also supported by the external ADC and DAC as per their user guide. If operated at a speed higher than 10kHz, it should end within the timer tick. 

    Regards, 
    Pranav Siddappa

  • 0 in reply to Pranav Siddappa
    Prodigy 20 points

    thank you for your reply
    I don't understand what you said.

    What I'm curious about is
    This is the difference between EMIF method and SPI method during PMSM motor control operation.
    Previously, all motor operations were processed within a 100us timer using the EMIF method.
    Will there be any problems with motor control when changing to SPI communication method?

    For example within a 100us cycle timer

    When sending and receiving a lot of data using EMIF
    When the same data is exchanged at the same cycle through SPI communication

    What is the difference?
    What effect will this have on precision control operations such as motors?

  • 0 in reply to ysgeum
    TI__Intellectual 2786 points

    Hi Ysgeum, 

    The main difference here lies in the fact that EMIF can transmit data parallelly whereas SPI does it sequentially.
    Can you let me know how many bytes of data you are feeding using EMIF into the DAC and ADC between each clock tick? Then I can better suggest if SPI would work for your use case.

    Regards, 
    Pranav Siddappa