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uart: TX_DONE occurs before transmission is complete. #33866

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zisisadamos opened this issue Mar 30, 2021 · 0 comments
Closed

uart: TX_DONE occurs before transmission is complete. #33866

zisisadamos opened this issue Mar 30, 2021 · 0 comments
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area: UART Universal Asynchronous Receiver-Transmitter bug The issue is a bug, or the PR is fixing a bug platform: STM32 ST Micro STM32

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@zisisadamos
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Describe the bug
TX_DONE event occurs before transmission is complete on STM32 async usart api.
ISSUE
In the attached image RTS pin state is controlled by the TX_DONE event. It is clear that the event is triggered before transmission is complete. This is because TX_DONE is generated when DMA finishes data transfer on transmit register and not when transmit register is empy.

To Reproduce
Steps to reproduce the behavior:

  1. Have a uart peripheral correctly configured in async mode.
  2. Use async TX and monitor TX_DONE event in conjuction with with tx line.
  3. Bug occurs.

Expected behavior
TX_DONE should occur when peripheral tx register is empty.

Impact
Showstopper

Environment (please complete the following information):
@zisisadamos zisisadamos added the bug The issue is a bug, or the PR is fixing a bug label Mar 30, 2021
@carlescufi carlescufi changed the title TX_DONE occurs before transmission is complete. uart: TX_DONE occurs before transmission is complete. Mar 30, 2021
@carlescufi carlescufi added area: UART Universal Asynchronous Receiver-Transmitter platform: STM32 ST Micro STM32 labels Mar 30, 2021
zisisadamos added a commit to zisisadamos/zephyr that referenced this issue Mar 30, 2021
@zisisadamos
drivers: uart: stm32: Fixes timing of TX_DONE generation.
4c70641 
Corrects TX_DONE generation occuring to early
on async api.
Fixes zephyrproject-rtos#33866
Signed-off-by: Zisis Adamos <[email protected]>
@galak galak added the has-pr label Mar 30, 2021
@nashif nashif closed this as completed in 7235b09 Mar 31, 2021
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area: UART Universal Asynchronous Receiver-Transmitter bug The issue is a bug, or the PR is fixing a bug platform: STM32 ST Micro STM32
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@zisisadamos @carlescufi @galak