External Camera with SPI bus

iabdalkader · April 30, 2019, 4:28pm

There a “!” in the if statement.

lak4cyut · May 2, 2019, 2:09am

NO!! Please take look!!
Your !DMA_BUFFER(src) is going to run non-DMA SPI APIs!!
This if statement is wrong logic!!

        if (len == 1 || query_irq() == IRQ_STATE_DISABLED || !DMA_BUFFER(src)) {
	    // !!!!!!!!!!!!!!!!  Read data directly !!!!!!!!!!!!!!!!!
        } else {
            // Read data with DMA  <-- But now the address is not aligned on 4 bytes.
        }

github.com

openmv/micropython/blob/20dec3960516a082e27b812827ffcaf72d2c6916/ports/stm32/spi.c#L455


      
          
          
STATIC void spi_transfer(const spi_t *self, size_t len, const uint8_t *src, uint8_t *dest, uint32_t timeout) {
              // Note: there seems to be a problem sending 1 byte using DMA the first
              // time directly after the SPI/DMA is initialised.  The cause of this is
              // unknown but we sidestep the issue by using polling for 1 byte transfer.
          
          
    // Note: DMA transfers are limited to 65535 bytes at a time.
          
          
    HAL_StatusTypeDef status;
          
          
    if (dest == NULL) {
                  // send only
                  if (len == 1 || query_irq() == IRQ_STATE_DISABLED || !DMA_BUFFER(src)) {
                      mp_uint_t atomic_state = MICROPY_BEGIN_ATOMIC_SECTION();
                      status = HAL_SPI_Transmit(self->spi, (uint8_t*)src, len, timeout);
                      MICROPY_END_ATOMIC_SECTION(atomic_state);
                  } else {
                      DMA_HandleTypeDef tx_dma;
                      dma_init(&tx_dma, self->tx_dma_descr, self->spi);
                      self->spi->hdmatx = &tx_dma;
                      self->spi->hdmarx = NULL;

lak4cyut · May 2, 2019, 3:03am

Wow… I am sorry, I saw your new version already removed DMA_BUFFER check.
So this bug is not exist anymore.
Thanks~~

kwagyeman · May 2, 2019, 4:54am

Ibrahim, can you check this carefully.

Thanks,

iabdalkader · May 2, 2019, 2:00pm

I don’t see the problem…

This is the DMA_BUFFER macro for the F7:

#define DMA_BUFFER(p) ((uint32_t)p & 3)

This is the if statement:

if (len == 1 || query_irq() == IRQ_STATE_DISABLED || !DMA_BUFFER(dest)) {

If the length of the buffer is 1 byte OR the IRQs are disabled OR it’s NOT a DMA buffer (not aligned) then read the data without using the DMA. Otherwise it’s more than 1 byte and IRQs are enabled and it’s aligned.

What is the problem ?

iabdalkader · May 2, 2019, 2:12pm

Oh I see the issue now, I actually fixed this bug before for the SDCARD but I forgot to fix it in the SPI code. This is the fixed macros:

#define ALIGNED_BUFFER(p)     (((uint32_t)p & 3) == 0)

#if defined(STM32H7)
// NOTE: H7 SD DMA can only access AXI SRAM.
#define DMA_BUFFER(p)       ((uint32_t) p >= 0x24000000 && (uint32_t) p < 0x24080000)
#elif defined(STM32F4)
// NOTE: F4 CCM is not accessible by GP-DMA.
#define DMA_BUFFER(p)       ((uint32_t) p > 0x10010000)
#else
// Assume it's DMA'able
#define DMA_BUFFER(p)       (true)
#endif

lak4cyut · May 9, 2019, 2:28am

^.^ I am happy to know I’m not crazy.

Topic		Replies	Views
OpenMV Cam to an Arduino Pro Mini OpenMV Boards	15	14966	January 19, 2017
4D systems dislpay + camera openmv OpenMV Boards	11	7220	July 28, 2018
LCD type OpenMV Boards	30	21023	July 3, 2019
4.5.8 Memory Leaks and abnormal behavior (on custom hardware with identical H7 plus components ) OpenMV Boards	98	924	August 12, 2025
two image in two openmv board similiarity compared OpenMV Boards	3	1041	June 17, 2020

External Camera with SPI bus

Related topics