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Original question:

MSP430FR6047: UCB0 for SPI doesn't work

MSP430FR6047: SPI signals are crooked or blurred

sukho suh
Intellectual 700 points
Part Number: MSP430FR6047
Other Parts Discussed in Thread: DAC7750, , DAC8760

Dear All;

I'm getting very dirty signals coming from USCB0 ports from  1,5 (SCLK) and 1.6 (SIMO) as below; The 1st channel (red) is SCLK and the 2nd channel (orange) is SIMO. 

I don't believe the DAC (slave) will recognize this at all;

Please help me.

  • 0
    Guru 100565 points

    I think your image didn't set properly. "Insert media" (the box with the circle) works more often than paste.

  • 0 in reply to Bruce McKenney
    Intellectual 700 points

    Oh, I knew the image was not properly shown (pasting) but didn't know how to correct it after finishing the message. I hope this time it's ok.

    The frequency is 1MHz. If I reduce it to 100 Khz, then it looks much better but there are still upshots at the rising edge.

    Please help me, sir.

  • 0 in reply to sukho suh
    Guru 24825 points

    I see nothing there that would cause trouble. In any case, the ringing could be from your scope probes: circuitcellar.com/.../

  • 0
    Prodigy 40 points

    SPI signal are not perfect square in real systems as they are drawn in technical sheets. Your signal may be considered in good form for real system.

    Do not underestimate your slave DAC, You can test your signal in several ways,

    -Find a static register and read register content and check if read data is same as document

    -Find a register that you are able to read what you write, just test write and read same data, change it in your code between write and read to be sure it is changed by SPI read

    -Write a register that has effect on slave behavior. Write the data and check the result.

    If one of these methods is not worked then try to fix your signal form. Before considering signal form, be sure it is not working, If it is working do not fix it.

  • 0 in reply to David Schultz
    Intellectual 700 points

    I read the material you linked skimpily because the contents there are overwhelming for me. But I think I get the picture.

    Then I think I'll have to move on.

    Thank you.

  • 0 in reply to Soner Sezgin
    Intellectual 700 points

    ok. Sir. That's exactly what I'm doing now but without any luck.

    I downloaded the 5444.DAC8760_Interface which is DAC8760 test program from TI, modified it for my MSP430FR6047 and DAC7750. I am trying to set the output value of DAC7750 but I don't see any change of value of the output.

    I scoped the STE, SCLK and SIMO pines and verified (at my level of knowledge) that the signals are going out to DAC7750 ok. But I don't receive anything on SOMI pin.

    I will study DAC7750 datasheet more and will definitely come back with another cry for help!!!

    Regards,

    Sukho

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