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

[grubygrub]

Posted on October 13, 2012 at 02:59

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.