TMS320F28P650DK: SPI High speed mode

Hi Jay,

I've run some tests using the TMS320F28P650 LaunchPad and custom boards, and I can share the following findings:

1. High-Speed Mode GPIOs:
   SPI high-speed mode is only supported on the specific GPIOs listed in Table 5-9 of the datasheet. Using other GPIOs — for example, GPIO124 for SPIC_CLK — will not enable high-speed mode. In my tests, non-HS GPIOs could handle up to approximately 12.5 MHz, sometimes slightly more, but with significant signal integrity issues at higher frequencies.
   From tech ref:
   

2. Pin Configuration with DriverLib/SysConfig:
   Yes, you can use standard DriverLib functions (and SysConfig does this automatically) to configure the required muxing and pad settings for SPI. For example:
   

   GPIO_setPinConfig(mySPI0_SPIPICO_PIN_CONFIG);
   GPIO_setPadConfig(mySPI0_SPIPICO_GPIO, GPIO_PIN_TYPE_STD);
   GPIO_setQualificationMode(mySPI0_SPIPICO_GPIO, GPIO_QUAL_ASYNC);

   These calls handle the pinmux and qualification settings correctly, including the ones needed for high-speed operation.

3. Configuration Notes:

   • LSPCLK = 100 MHz

   • SPI Clock = 20 MHz

   • SPI configured in high-speed mode

   • But non-HS GPIOs used for SPI signals

   This configuration will not enable true high-speed mode. Even if the SPI module is set to HS mode internally, the physical pins must be from the HS-capable set for the high-speed buffers to be enabled. Otherwise, the signal integrity and timing margins will degrade quickly above ~12.5 MHz.

   Conclusion:
   To benefit from SPI high-speed mode, you must use the specific HS-capable GPIOs listed in the technical reference manual. The DriverLib/SysConfig tools are fully capable of configuring them properly.

   Best regards,
   Sebastián