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Question asked by Barta.Hank on Oct 22, 2015
Latest reply on Nov 20, 2015 by gebert.rafael
Hi folks,
We're using an STM32F429I to drive an LCD using H/W similar enough to the STM32F429I-DISCO board so that I was able to get this working by using the STemWin BSP files from one of the demos. (Some tweaking was required to accommodate MX initialization and different display resolution.)

I would like to implement double buffering to solve some display issues we are experiencing. I have found where the BSP code swaps buffers in LCDConf_stm32f429i.c in void HAL_LTDC_LineEvenCallback(LTDC_HandleTypeDef *hltdc). Unfortunately that code never executes, as if we are not configured for the interrupt. 

Examining the device configuration in MX I see that we are configured for both LTDC global interrupt and LTDC global error interrupt. (The error interrupt sometimes fires on startup but otherwise seems to do no harm.)

Is there something else that needs to be done to enable the VSYNC or line (HSYNC?) interrupt? I looked at the API calls in stm32f4xx_hal_ltdc.c and saw nothing that seemed to relate to enabling interrupts. They are configured and enabled in ltdc.c (HAL_NVIC calls.) LTDC_IRQHandler(void) is defined in stm32f4xx_it.c and calls HAL_LTDC_IRQHandler() which eventually calls HAL_LTDC_LineEvenCallback() so it seems that everything is in place.

What could we be missing that interferes with the line event callback?