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I2s receive 24bit in 32bit frame using HAL on stm32f411re

Question asked by p.m.002 on Apr 28, 2016
Hello,
I am trying to read a digital mems microphone that sends 24 bit via i2s. My problem is that I only receive 16 bit values and that the hal documentation is kind of confusing to me (probably because I am new to microcontroller programming). \\
I tried:\\
uint8_t sample=2;
uint16_t I2S_RX_BUFFER2[sample];
ReadStatus= HAL_I2S_Receive(&hi2s1, (uint16_t*)I2S_RX_BUFFER2, sample, 0x1000);
The values I get are between 0 and 65.535.\\

The relevant documentation:\\

**
  * @brief Receive an amount of data in blocking mode
  * @param  hi2s: pointer to a I2S_HandleTypeDef structure that contains
  *         the configuration information for I2S module
  * @param pData: a 16-bit pointer to data buffer.
  * @param Size: number of data sample to be sent:

""""This note confuses me:"""
  * @note When a 16-bit data frame or a 16-bit data frame extended is selected during the I2S
  *       configuration phase, the Size parameter means the number of 16-bit data length
  *       in the transaction and when a 24-bit data frame or a 32-bit data frame is selected
  *       the Size parameter means the number of 16-bit data length.
 [ ...]
HAL_StatusTypeDef HAL_I2S_Receive(I2S_HandleTypeDef *hi2s, uint16_t *pData, uint16_t Size, uint32_t Timeout)

So my question is what did I do wrong when setting the parameters and how can I improve it.

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