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SD card on K21

Question asked by Evgeni Kosakovski on Apr 4, 2020
Latest reply on Apr 5, 2020 by Evgeni Kosakovski

Hello.

Currently, I am working on TWR-K21 with the Kinetis K21 microcontroller and using sample NXP project sdcard_fatfs through SDIO. When running project I see the following situation:
After turning 'ON' the SD clock in the SDHC_SetClock () function, the pin CLK starts working without stopping.
The first SetIdle () command passes and the next SendInterfaceCondition () command returns an error.
I see that the data goes through the CMD pin, but it does not give anything.

Before that, I did a similar project on TWR-K60 (with different drivers) and everything worked. Therefore, I compared 2 protocols on the scope and saw that the K60 clock works only during data transfer and on K21 clock works all the time.
Maybe this will solve the problem of working with the SD card. 

How to find the reason that CLK is constantly working?

Project is attached.

Thanks.

Evgeni

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