[GitHub] [incubator-nuttx] patacongo commented on issue #3665: stm32l467-DISCO:nsh Serial not working 100% with permutations of HW FC (both on chip and GPIO) /DMA

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patacongo commented on issue #3665:
URL: https://github.com/apache/incubator-nuttx/issues/3665#issuecomment-833531356


   > t drops chars with HW flow control (on chip).
   
   Isn't that due to the lack of RX/TX FIFOs on the serial peripheral?  That causes this bad behavior if the chip hardware flow control is enabled:  https://github.com/apache/incubator-nuttx/blob/master/arch/arm/src/stm32/Kconfig#L9409 and https://github.com/apache/incubator-nuttx/blob/master/arch/arm/src/stm32l4/Kconfig#L5656
   
    The H7 (and maybe others) do have FIFOs and should not required the FLOWCONTROL_BROKEN kludge.
   
   That little circular RX DMA was added by Mike Smith to account for data losses because of the lack of Rx FIFOs on the STM32 F4 family.  It should not be necessary if the U[S]ART peripheral has hardware FIFOs.  The original H7 did not support this circular DMA (as I recall) because it was not needed.
   
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