Serial.flush modification (esp8266#5293)

* Modify Serial.flush

* Add function to uart tests

Author: dsv19

cores/esp8266/HardwareSerial.cpp

@@ -108,14 +108,16 @@ int HardwareSerial::available(void)
 
 void HardwareSerial::flush()
 {
+    uint8_t bit_length = 0;
     if(!_uart || !uart_tx_enabled(_uart)) {
         return;
     }
 
+    bit_length = uart_get_bit_length(_uart_nr); // data width, parity and stop
     uart_wait_tx_empty(_uart);
     //Workaround for a bug in serial not actually being finished yet
     //Wait for 8 data bits, 1 parity and 2 stop bits, just in case
-    delayMicroseconds(11000000 / uart_get_baudrate(_uart) + 1);
+    delayMicroseconds(bit_length * 1000000 / uart_get_baudrate(_uart) + 1);
 }
 
 void HardwareSerial::startDetectBaudrate()

cores/esp8266/uart.cpp

@@ -48,6 +48,10 @@
 #include "user_interface.h"
 #include "uart_register.h"
 
+#define MODE2WIDTH(mode) (((mode%16)>>2)+5)
+#define MODE2STOP(mode) (((mode)>>5)+1)
+#define MODE2PARITY(mode) (mode%4)
+
 /*
   Some general architecture for GDB integration with the UART to enable
   serial debugging.
@@ -204,7 +208,14 @@ uart_read_char_unsafe(uart_t* uart)
     return -1;
 }
 
-size_t
+uint8_t
+uart_get_bit_length(const int uart_nr)
+{
+    // return bit length from uart mode, +1 for the start bit which is always there. 
+    return MODE2WIDTH(USC0(uart_nr)) + MODE2PARITY(USC0(uart_nr)) + MODE2STOP(USC0(uart_nr)) + 1;
+}
+
+size_t 
 uart_rx_available(uart_t* uart)
 {
     if(uart == NULL || !uart->rx_enabled)

cores/esp8266/uart.h

@@ -147,6 +147,7 @@ int uart_get_debug();
 void uart_start_detect_baudrate(int uart_nr);
 int uart_detect_baudrate(int uart_nr);
 
+uint8_t uart_get_bit_length(const int uart_nr);
 
 #if defined (__cplusplus)
 } // extern "C"

tests/host/common/MockUART.cpp

@@ -313,6 +313,15 @@ uart_get_baudrate(uart_t* uart)
 	return uart->baud_rate;
 }
 
+uint8_t
+uart_get_bit_length(const int uart_nr)
+{
+	uint8_t width = ((uart_nr % 16) >> 2) + 5;
+	uint8_t parity = (uart_nr >> 5) + 1;
+	uint8_t stop = uart_nr % 4;
+	return (width + parity + stop + 1);
+}
+
 uart_t*
 uart_init(int uart_nr, int baudrate, int config, int mode, int tx_pin, size_t rx_size)
 {