HardwareSerial - availableForWrite() support (espressif#1226)

* HardwareSerial - availableForWrite() support * fix indentation errors (tab vs space)

Author: mtabu

cores/esp32/HardwareSerial.cpp

@@ -62,6 +62,10 @@ int HardwareSerial::available(void)
 {
 returnuartAvailable(_uart);
 }
+intHardwareSerial::availableForWrite(void)
+{
+returnuartAvailableForWrite(_uart);
+}
 
 intHardwareSerial::peek(void)
 {

cores/esp32/HardwareSerial.h

@@ -40,6 +40,7 @@ class HardwareSerial: public Stream
 voidbegin(unsignedlong baud, uint32_t config=SERIAL_8N1, int8_t rxPin=-1, int8_t txPin=-1, bool invert=false);
 voidend();
 intavailable(void);
+intavailableForWrite(void);
 intpeek(void);
 intread(void);
 voidflush(void);

cores/esp32/esp32-hal-uart.c

@@ -248,6 +248,14 @@ uint32_t uartAvailable(uart_t* uart)
 returnuxQueueMessagesWaiting(uart->queue);
 }
 
+uint32_tuartAvailableForWrite(uart_t*uart)
+{
+if(uart==NULL){
+return0;
+ }
+return0x7f-uart->dev->status.txfifo_cnt;
+}
+
 uint8_tuartRead(uart_t*uart)
 {
 if(uart==NULL||uart->queue==NULL){

cores/esp32/esp32-hal-uart.h

@@ -55,6 +55,7 @@ uart_t* uartBegin(uint8_t uart_nr, uint32_t baudrate, uint32_t config, int8_t rx
 voiduartEnd(uart_t*uart);
 
 uint32_tuartAvailable(uart_t*uart);
+uint32_tuartAvailableForWrite(uart_t*uart);
 uint8_tuartRead(uart_t*uart);
 uint8_tuartPeek(uart_t*uart);