title: STM32F205 SPI RXNE flag is not set
body: <p>I'm using STM32F205's SPI1 in master mode. And the RXNE flag is never set during transactions. Here's a part of SPI initialization:</p>
  
  <pre><code>SPI1-&gt;CR1 = SPI_CR1_MSTR | SPI_CR1_SSI | SPI_CR1_SSM | SPI_CR1_SPE;
  SPI1-&gt;CR2 = 0;
  </code></pre>
  
  <p>Then I'm trying to perform transmition/receiving of a single byte:</p>
  
  <pre><code>while(!(SPI1-&gt;SR &amp; SPI_FLAG_TXE)) {}  // wait for compeltion of the previous Tx
  SPI1-&gt;DR = 0xAB;                      // transmit some byte
  
  while(!(SPI1-&gt;SR &amp; SPI_FLAG_RXNE)) {}  // wait for byte to be received
  uint8_t result = SPI1-&gt;DR;
  </code></pre>
  
  <p>This code stucks at the waiting for RXNE flag. I tried to wait for busy flag <code>BSY = 0</code> instead of <code>RXNE = 1</code> and SPI began to work. It seems RXNE is never set.</p>