After reset, the 1.8V interface cannot be used again without physical power control on the SD card.

[joseph5760]

I have a question about controlling the SD card through the NXP SDK.

When the first power is applied and the SD card is initialized, S18A responds with 1 in response to ACMD41. So it can be converted to 1.8V.

However, if reset the MCU, it will respond to ACMD41 as
command.response[0U] = 0xC0FF8000 (24th bit is 0)
So the 1.8V conversion fails and the IO speed of the SD card is limited to 50 MHz.
Probably already at 1.8V, the S18A response seems to be zero.

Is there a way to check if it has already been initialized to 1.8V so that a correct re-initialization is possible?

[kerryzhou]

Hi @joseph5760 

   Do you check the MIMXRT1060-EVK board, with the SDK, whether still have you mentioned issues or not?

   Do you also check your sd card communicate wave, if the POR and the reset, any different or not?

Best Regards,

Kerry

[joseph5760]

I am using a non-EVK 3rd party board (Teensy 4.1).
In EVK, there is no problem by controlling the power of the SD card, but in this board, power control is not possible because the SD card is always connected to 3.3V.

I want to know how to reset without SD card power control.

[kerryzhou]

Hi @joseph5760 

  You are right, the EVK is default using the 3.3V.

   Your Teensy 4.1 is 1V8, right?

   If you reset the chip, plug off the sd card, insert the sd card again, whether that works or not?

Best Regards,

Kerry