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Original question:

LAUNCHXL-F280049C: ADC clock this clock

LAUNCHXL-F280049C: X2 GPIO-18

Genatco
Guru 56043 points
Part Number: LAUNCHXL-F280049C


Reviewing the datasheet clock sources noticed Fig.7-13 shows XTAL pins X1, X2 and Launch pad schematic GPIO18 could be sent to booster header, not by default.

Then I see SDK-FOC motor SW configured GPIO-18 as an input but after MOSC was configured.

Should SW configure GPIO18 for use as X2 pin, GPIO_18_XCLKOUT or remove below configuration? What kind of mayhem does GPIO18 being configured cause when X2 is the XTAL or resonator input?

  // GPIO18->Reserve (N/A for GPIO)
GPIO_setMasterCore(18, GPIO_CORE_CPU1);
GPIO_setPinConfig(GPIO_18_GPIO18); //GPIO_18_XCLKOUT
GPIO_setDirectionMode(18, GPIO_DIR_MODE_IN);
GPIO_setPadConfig(18, GPIO_PIN_TYPE_STD);  

  • +1
    TI__Mastermind 28275 points

    Hi GI,

    When the XTAL is being used (i.e OSCOFF = 0), X2/GPIO18 pin becomes X2 so whatever GPIO18 is configured to has no effect.

  • 0 in reply to Frank Ankapong
    Guru 56043 points

    Hi Frank,

    But how can GPIO18 even be used when MOSC is an XTAL, removing R35 and place 0R on R31, R38 as shown in launch pad schematic. R35 is DNP anyway with XTAL on X2. Do we have to remove the XTAL and use the internal clock?

    Thanks Frank

  • +1 in reply to Genatco
    TI__Mastermind 28275 points

    So if you are using an XTAL, GPIO18 is not available for use as XTAL requires both X1 and X2/GPIO18. However if you are not using an XTAL but rather INTOSC2, then GPIO18 is available for use.

    To use GPIO18 (i.e application not using XTAL), remove R31 and install 0ohm to R28 (GPIO18_BP). You don't need to remove the XTAL but you will need to install a 1kohm on R35. This 1kohm will act as a pull-down to satisfy the X1 pull-down requirement highlighted in the TRM.

    Let us know if this is still not clear.

  • 0 in reply to Frank Ankapong
    Guru 56043 points
    Frank Ankapong said:
    However if you are not using an XTAL but rather INTOSC2, then GPIO18 is available for use.

    That was sort of the question as to how the schematic comment makes since to use GPIO18 with an active XTAL too. The note assumes the reader has knowledge INTOS2 is mandated to route GPIO18 to booster headers. I sort of suspected such but thanks again for confirming the method to use GPIO18 is more intricate  Relaxed

  • +1 in reply to Genatco
    TI__Mastermind 28275 points

    Glad to help GI. I will check with the launchpad team to see if they can update and clarify the note in the schematic.