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Update UART

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Lee Lup Yuen 2023-05-11 16:00:55 +08:00
parent e401a44805
commit a35de2e803
1 changed files with 16 additions and 2 deletions
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README.md
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@ -1107,20 +1107,34 @@ To support multiple UART Ports, we copied the following functions from the [Allw
- [`arm64_earlyserialinit`](https://github.com/lupyuen2/wip-pinephone-nuttx/blob/uart3/arch/arm64/src/a64/a64_serial.c#L1323-L1398)
(Init the UART Ports)
- [`a64_uart_init`](https://github.com/lupyuen2/wip-pinephone-nuttx/blob/uart3/arch/arm64/src/a64/a64_serial.c#L944-L996)
(Init the UART Pins. Called by [`arm64_earlyserialinit`](https://github.com/lupyuen2/wip-pinephone-nuttx/blob/uart3/arch/arm64/src/a64/a64_serial.c#L1323-L1398))
- [`a64_uart_setup`](https://github.com/lupyuen2/wip-pinephone-nuttx/blob/uart3/arch/arm64/src/a64/a64_serial.c#L453-L582)
(Configure the UART Port. Called when the UART Port is opened)
- [`a64_uart_irq_handler`](https://github.com/lupyuen2/wip-pinephone-nuttx/blob/uart3/arch/arm64/src/a64/a64_serial.c#L301-L415)
(UART Interrupt Handler)
- [`a64_uart_receive`](https://github.com/lupyuen2/wip-pinephone-nuttx/blob/uart3/arch/arm64/src/a64/a64_serial.c#L727-L753)
[(Here's the log)](https://github.com/lupyuen2/wip-pinephone-nuttx-apps/blob/e5aa2baba64c8d904d6c16b7c5dbc68cd5c8f1e1/examples/hello/hello_main.c#L72-L270)
(Receive UART Data)
Inside the UART Driver, be careful when logging to the UART Port! If the UART Port is busy doing logging, it won't allow us to the Baud Rate...
[(Here's the log)](https://github.com/lupyuen2/wip-pinephone-nuttx-apps/blob/e5aa2baba64c8d904d6c16b7c5dbc68cd5c8f1e1/examples/hello/hello_main.c#L72-L270)
Inside the UART Driver, be careful when logging to the UART Port!
If the UART Port is busy doing logging, it won't allow us to the Baud Rate...
> "This register may only be accessed when the DLAB bit (UART_LCR[7]) is set and the UART is not busy (UART_USR[0] is zero)"
[(Allwinner A64 User Manual, Page 564)](https://lupyuen.github.io/images/Allwinner_A64_User_Manual_V1.1.pdf)
That's why we always wait for UART Not Busy before setting the Baud Rate. [(Like this)](https://github.com/lupyuen2/wip-pinephone-nuttx/blob/uart3/arch/arm64/src/a64/a64_serial.c#L417-L451)
_What happens if UART Is Busy when we set the Baud Rate?_