ECSPI skipping a byte while sending data from slave to master

[harish_g]

Hi ,

I am trying to communicate with two imx7d Sabre SD boards using ECSPI. The master board sent a "Hello World" and the slave in return sent a "Hello World" in the sample program. The slave is first allowed to fill its TXFIFO, after which master initiates the transactions. While the master sends all the bytes properly, the slave omits the first byte and starts to send data from the second byte onwards. I have attached the code which created this problem. Is there any specific reason, why this happens or is it something which is wrong with my code?  

Regards ,

G.Harish

[Carlos_Musich]

Hi harish,

how are you doing your testing? How do you know the slave is missing the first byte to send and not the master which is loosing the first byte when receiving?

[harish_g]

Hi Carlos,

              One of the methods i tried to debug was with a CRO by probing the MISO,MOSI and SCLK lines . What i saw was, during the first cycle ( i.e. First burst ), the slave also was sending a byte while the master was pushing its data into the slave. Also, the prints i used, proved that the byte which arrives first in the Master, arrives during the very first burst initiated by the master. So, using these two clues, i identified that the slave itself sends the second byte without sending the first byte.

Regards,

G.Harish

[Carlos_Musich]

Hi harish,

you can download FreeRTOS BSP for imx6sx and you will find there an ecspi driver demo that will be compatible with imx7d.

Regards,
Carlos

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