Posted on May 17, 2011 at 13:07I want to use the DAC to output some audio samples.
I have configure the DAC like this:
----------------------------------------------
DAC_StructInit (&dac_init);
dac_init.DAC_Trigger = DAC_Trigger_T6_TRGO;
dac_init.DAC_WaveGeneration = DAC_WaveGeneration_None;
dac_init.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
DAC_Init (DAC_Channel_1, &dac_init);
----------------------------------------------
I am using DMA to output the samples. I have one version for 8 bit samples:
----------------------------------------------
dma_init.DMA_PeripheralBaseAddr = reinterpret_cast(&(DAC->DHR8R1));
dma_init.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
dma_init.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
----------------------------------------------
And one for 12 bit samples.
----------------------------------------------
dma_init.DMA_PeripheralBaseAddr = reinterpret_cast(&(DAC->DHR12R1));
dma_init.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word;
dma_init.DMA_MemoryDataSize = DMA_MemoryDataSize_Word;
----------------------------------------------
If I output the same samples (the samples are shifted by 4 for the 12 bit version), the 12 bit version is much louder (higher amplitude).
Reading the reference manual I would expect both variants to create the same amplitude.
