RT1064: Resolving conflicts between SEMC and USDHC2

[axelrietschin]

Hi,

I'm learning to use the configuration tool (and everything else) and I would like to route both the SEMC and USDHC2. They compete for pin [D6] GPIO_EMC_38.

I suppose I should give priority to the SEMC. Does that mean I can not use the USDHC2, which needs the pin for its VSELECT function?

Is there a workaround for this case, i.e. use a GPIO configured as Output for USDHC2's VSELECT, and somehow inform the driver to use that particular pin for what appears to be a simple function, or maybe I can leave the eMMC chip in it's 3.3V power-on default?

USDHC1 also conflicts with the SEMC's clock, is it really that I must choose between using SDRAM or using MMC's?

Please advise, thanks!

[jingpan · Accepted solution]

Hi @axelrietschin ,

Yes, USDHC2_VSELECT and SEMC_DM1 both are mux to GPIO_EMC_38 only.  VSELECT functionality can be replaced with a GPIO, VSELECT is optional for system implementation and it requires a control circuit to change the voltage.
 
As you can see in the NVCC_SD section of the EVK schematics when the VSELECT pin is high it will turn on the transistor and the 234K resistor in parallel will be activated. As a result we will have NVCC_SD with 1.8V. This same behavior could be implemented with a GPIO as well.

And as I can see, SEMC_CLK doesn't conflict with any of USDHC1 pin.

Regards,

Jing

[axelrietschin]

Awesome, thanks!