Add DMA support for STM32L4xx series (CSELR-based request routing) #3872
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The STM32L4xx series uses a channel-based DMA with CSELR (Channel Selection Register) for request routing, distinct from F2/F4/F7 (stream+channel), F1 (hardwired channels), and L4+ (DMAMUX). Header (TFT_eSPI_STM32.h): - Add STM32L4xx detection block between F1xx and the fallback - Define STM32_DMA to enable DMA code paths - Map SPI1_TX to DMA1_Channel3, SPI2_TX to DMA1_Channel5 Source (TFT_eSPI_STM32.c): - Add DMA IRQ handlers for STM32L4 (DMA1_Channel3/5) - Add initDMA() with CSELR routing via DMA_REQUEST_1 - Set spiHal.State = HAL_SPI_STATE_READY before first use, since spiHal is a separate handle from Arduino's internal SPI and only has Instance set via INIT_TFT_DATA_BUS. Without this, HAL_SPI_Transmit_DMA silently returns HAL_BUSY on every call. Tested on STM32L412KB with ST7735 80x160 display on SPI1 at 40MHz. Co-Authored-By: Claude Opus 4.5 <[email protected]>
Bodmer
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Feb 12, 2026
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Looks good, thanks for the input to the library.
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The STM32L4xx series uses a channel-based DMA with CSELR (Channel Selection Register) for request routing, distinct from F2/F4/F7 (stream+channel), F1 (hardwired channels), and L4+ (DMAMUX).
Header (TFT_eSPI_STM32.h):
Source (TFT_eSPI_STM32.c):
Tested on STM32L412KB with ST7735 80x160 display on SPI1 at 40MHz.