Connection status issue corrected. If the link layer status changes,
the connection status callback is now called correctly.
mbedtls headers from library are removed and the mbed-os one's are used.
When using UARTSerial sending data over the uart follows the sequence
below:
<-TX done ISR runs and sets a software interrupt to pending
<-Software interrupt fires:
-disables TX done interrupt
-calls UARTSerial TX handler which sends bytes until the uart
buffer filled (writeable returns false). Sending a byte
re-enables the TX done interrupt continuing the cycle
Due to this sequence, if the UARTSerial TX handler does not send a byte
then the transmit state machine mentioned above will get stuck with
the TX done interrupt disabled. The events causing this failure:
<-TX done ISR runs and sets a software interrupt to pending
<-Software interrupt fires:
-disables TX done interrupt
-calls UARTSerial TX handler:
-checks writeable which is true and sends a byte
<- interrupted by a higher priority interrrupt
<- TX done ISR runs, setting software interrupt to
pending again
-checks writeable which is true and sends a second byte
-Software interrupt finishes
<-Software interrupt fires:
-disables TX done interrupt
-calls UARTSerial TX handler:
-checks writeable which is false and DOES NOT SEND A BYTE
-Software interrupt finishes, the TX interrupt is still disabled
*-Byte gets sent but TX done ISR does not fire
This patch prevents the TX lockup by removing the code in the
software interrupt which disables the TX done interrupt. Disabling the
TX done interrupt at this point is not necessary so this code is safe
to remove.
With support for checking H/W UART initialized or not, we can simplify stdio management:
1. When serial_init(&stdio_uart) calls in, just set the 'stdio_uart_inited' flag.
2. When serial_free(&stdio_uart) calls in, just clear the 'stdio_uart_inited' flag.
Except above, we needn't make special handling with 'stdio_uart'.
The same H/W UART may be shared by multiple serial_t objects. This fix tries to avoid
re-configuring the same H/W UART in serial_init() when there are multiple serial_t
objects constructed. To re-configure UART, call serial_baud() and serial_format()
explicitly. This can avoid confusion when e.g. a newly constructed serial_t object
changes baudrate unexpectedly in serial_init().