F4 Series SPI HAL Data Size Bug

[Enforcer83]

I am getting a warning during compile of an incompatible pointer type when I call the SPI TransmitReceive function as shown below.Compiler warning

I am passing the function an unsigned 16 bit integer array.  I have configured the SPI to use 16 data bits, as shown below in CubeMX.

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While digging into the HAL functions, I noticed that all the Transmit and Receive functions were expecting a pointer to an unsigned 8 bit value, shown below.  If the SPI peripheral is suppose to be able to accept either 8 or 16 data bits, wouldn't the expected type be the maximum size it can accept or two different sets of functions for either 8 data bits or 16 data bits?

 

[TDK]

Cast the pointer to uint8_t* when you pass it:

HAL_SPI_TransmitReceive(adc->_spiHandle, (uint8_t*) txBuf, (uint8_t*) rxBuf, 8, HAL_MAX_DELAY);

 

There's no way to accept two different types as an argument in C. They could have made it a void pointer, but that has its own issues.

[Pavel A.]

Maybe even cast to void* right in the invocation

HAL_SPI_TransmitReceive(adc->_spiHandle, (void*) txBuf, (void*) rxBuf, ...)

 

[Andrew Neil]

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@Enforcer83 wrote:

While digging into the HAL functions, ...

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You need to dig a little deeper.

You'll see that, inside the function, it checks whether the SPI is configured for 8 or 16 bits, and behaves accordingly

 

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@Enforcer83 wrote:

wouldn't the expected type be the maximum size it can accept

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No - then it wouldn't work for 8-bit data (it would skip every other byte).

16-bit data is just pairs of 8-bit bytes - so uint8_t is used as the "lowest common denominator".