missing one byte out of 26 while receiving data with spi

[SA.17]

I am using STM32L072RB

I am receiving 26 bytes at one go from an adc using spi interface

but i found that i miss one byte out of 26 bytes(from any position) every 6-7 times of reading adc.

I saw that data byte is present using oscillosope ,but mcu misses it somehow.

I am using below code to receive each byte of data .i call it 26 times and save result in an array.

i am transmitting 0's only(c=0)

__STATIC_INLINE uint8_t spi2_read_write(unsigned char c)
{
uint8_t x; 
while(!(SPI2->SR&(1<<1))){;} 
GPIOB->BRR = GPIO_PIN_12 ;  // CS LOW
SPI2->DR=c; 
while(!(SPI2->SR&(1<<1))){;} 
while(!(SPI2->SR&(1<<0))){;}
x=SPI2->DR; 
while(SPI2->SR&(1<<7)){;} 
GPIOB->BSRR = GPIO_PIN_12 ;  //CS high
	
return x;
}

one more issue with above code:

when i start reading ,first byte(of 26 bytes) is always the one which i received last during previous read.And i always miss the last byte during my current read.

How to resolve this ?

to ignore this issue What i am doing is reading 27 instead of 26 bytes and hence ignoring the first byte always (which is 0). but its not good solution i guess

May be this issue is causing missing byte issue ?

[waclawek.jan]

Do you observe SPI registers in debugger? Don't.

JW

[SA.17]

found that when i print SPI2->SR (status register) on line 12 of above code

SPI2->SR = 3 always

but the point it misses a data byte

it becomes SPI2->SR=2 and continuous to be 2 till next cycle of 26 bytes ,

even if i miss only one byte ,not only that time ,but also till the 26th byte SR remains 2 (even though i am getting correct data)

found by reading data received and matching with SR status ,

as one byte is missed ,rest data shifts upwards in my array

[TDK]

You could read DR prior to transmitting to clear the RXNE bit. If you have spurious clock edges, this may fix it. I don't see any problems with the code you posted.

[waclawek.jan]

> SPI2->SR = 3 always

So, after a TX/RX cycle, you *normally* see *both* TXE and RXNE set? That doesn't sound right.

Reduce the program to absolute minimum exhibiting the problem, but still complete compilable, and post.

JW