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va_args, printf, dma memory problem, possible misalignment or linker issue

Question asked by g.k.001 on Oct 13, 2012
I've been scratching my head for the past few days as I try to 
understand why and what is going on... So here it goes:


Current config: stm32f407VG (same as stm32f4 discovery)


I set up a project using the default linker and startup files from 
www.onarm.com.


Init the ADC & DMA's
       ADC_CommonInitStructure.ADC_Mode = ADC_DualMode_RegSimult;
       ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2;
       ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_1;


        DMA_InitTypeDef DMA_InitStructure;
        NVIC_InitTypeDef NVIC_InitStructure;


        DMA_InitStructure.DMA_Channel = DMA_Channel_0;
        DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t) &RawADCData.adcRaw1;
        DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t) ADC_CCR_ADDRESS;
        DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
        DMA_InitStructure.DMA_BufferSize = ADC_SAMPLE_NUM * ADC_NUM * ADC_BUFFER_MULTIPLIER;
        DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
        DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
        DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
        DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
        DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
        DMA_InitStructure.DMA_Priority = DMA_Priority_High;
        DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Enable;
        DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
        DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
        DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
        DMA_Init(DMA2_Stream0, &DMA_InitStructure);


        /*Interrupt when half of DMA is done, so we do not overwrite our values when processing*/
        DMA_ITConfig(DMA2_Stream0, DMA_IT_HT | DMA_IT_TC, ENABLE);
        DMA_ClearITPendingBit(DMA2_Stream0, DMA_IT_TEIF0 | DMA_IT_DMEIF0 | DMA_IT_FEIF0 | DMA_IT_TCIF0 | DMA_IT_HTIF0);


        // Enable the DMA2_Stream0 global Interrupt
        NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream0_IRQn;
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
        NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
        NVIC_Init(&NVIC_InitStructure);


        /* DMA2_Stream0 enable */
        DMA_Cmd(DMA2_Stream0, ENABLE);




--Symptom A:
Compile on GCC with CooCox as IDE, the DMA values are all garbled, after 
looking at the memory, it seems like the DMA values were sometimes 
offset by 1 word.




--Symptom B: Floats do not print correctly, printf works, but they are 
not passed on VA_ARGS correctly, offset by x bytes, x is pretty random.




--Sympton C: I add a struct into my file somewhere, say

struct b 
{
 float z[40];
}



Everything begins to work, prints are correct, DMA is correct.


I add anther struct into anther file
struct b 
{
 float z[80];
 int z[3];
}



DMA is correct, but printf does not work again. If i twitter around with 
the structs, DMA can be broken, but printf works, or they all can be 
broken.


I have a feeling that it is a linker error or alignment error, but do 
not know where else to look.


The entire codebase is here 
(http://code.google.com/p/narwhalroboticsquad/source/browse/?r=25#svn%2Ftrunk%2FNarwhalQuad)
 built with the GNU ARM toolchain.

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