Posted on December 07, 2017 at 07:52We encountered a problem with the ST’s MCU (STM32F767IGK6).
Problem description:
We are trying to read data from a camera sensor that is on our board (OV7740) connected to the STM32F7 DCMI port.
The data is being read from the camera, however it is somewhat disrupted, for example a frame byte that should read 255 (decimal) is received as 252 (decimal) and so on( we are using the camera’s “test pattern� which sends predefined known data).
The data is read from the camera and transferred using DMA from DCMI to external sram, 16 bit address, connected using FMC.
Tests findings:
During our extensive tests we narrowed the problem to either the DCMI port, or the DMA mechanism:
Hardware verification: Verified on 2 separate boards, and also on ST’s evaluation kit STM32F769I-EVAL (the kit is connected to a header board of OV7740). (Note: the evaluation kit has different hardware design than our hardware, the SRAM is different, camera is connected on different pins etc…) Result is the same on all three.
Lowest/highest frame rate (reducing system clock to justify the frame rate). Same results for all frame rates.
Define DCMI to 8 bit and to 10 bit: both modes showed erroneous data (We have 10 bit and 8 bit data formats).
Verify OV7740 configuration with Omnivision support, and also compared to omnivision’s evaluation kit configuration which is working.
DCMI configuration:
hdcmi.Instance = DCMI;
hdcmi.Init.SynchroMode = DCMI_SYNCHRO_HARDWARE;
hdcmi.Init.PCKPolarity = DCMI_PCKPOLARITY_FALLING;
hdcmi.Init.VSPolarity = DCMI_VSPOLARITY_HIGH;
hdcmi.Init.HSPolarity = DCMI_HSPOLARITY_LOW;
hdcmi.Init.CaptureRate = DCMI_CR_ALL_FRAME;
hdcmi.Init.ExtendedDataMode = DCMI_EXTEND_DATA_8B;
hdcmi.Init.JPEGMode = DCMI_JPEG_DISABLE;
hdcmi.Init.ByteSelectMode = DCMI_BSM_ALL;
hdcmi.Init.ByteSelectStart = DCMI_OEBS_ODD;
hdcmi.Init.LineSelectMode = DCMI_LSM_ALL;
hdcmi.Init.LineSelectStart = DCMI_OELS_ODD;
DMA configuration:
hdma_dcmi.Instance = DMA2_Stream1;
hdma_dcmi.Init.Channel = DMA_CHANNEL_1;
hdma_dcmi.Init.Direction = DMA_PERIPH_TO_MEMORY;
hdma_dcmi.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_dcmi.Init.MemInc = DMA_MINC_ENABLE;
hdma_dcmi.Init.PeriphDataAlignment = DMA_PDATAALIGN_WORD;
hdma_dcmi.Init.MemDataAlignment = DMA_MDATAALIGN_HALFWORD;
hdma_dcmi.Init.Mode = DMA_NORMAL;
hdma_dcmi.Init.Priority = DMA_PRIORITY_HIGH;
hdma_dcmi.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
hdma_dcmi.Init.FIFOThreshold = DMA_FIFO_THRESHOLD_FULL;
hdma_dcmi.Init.MemBurst = DMA_MBURST_SINGLE;
hdma_dcmi.Init.PeriphBurst = DMA_PBURST_SINGLE;
The rest of the code is based on ST’s STM32F7 formal snapshot example.
I found two other posts that are relevant to my problem although it is on F4 not F7:
https://community.st.com/0D50X00009XkeLMSAZ
https://community.st.com/0D50X00009XkXKPSA3
Thanks is advance.
#fmc #dma #dcmi #sram #stm32f7
