Adds functionality allowing size of HardwareSerial's RX buffer to be changed at runtime.

cores/esp32/HardwareSerial.cpp

@@ -46,6 +46,10 @@ void HardwareSerial::end()
     _uart = 0;
 }
 
+size_t HardwareSerial::setRxBufferSize(size_t new_size) {
+    return uartResizeRxBuffer(_uart, new_size);
+}
+
 void HardwareSerial::setDebugOutput(bool en)
 {
     if(_uart == 0) {

cores/esp32/HardwareSerial.h

@@ -70,6 +70,7 @@ class HardwareSerial: public Stream
     uint32_t baudRate();
     operator bool() const;
 
+    size_t setRxBufferSize(size_t);
     void setDebugOutput(bool);
 
 protected:

cores/esp32/esp32-hal-uart.c

@@ -240,6 +240,26 @@ void uartEnd(uart_t* uart)
     uartDetachTx(uart);
 }
 
+size_t uartResizeRxBuffer(uart_t * uart, size_t new_size) {
+    if(uart == NULL) {
+        return;
+    }
+
+    UART_MUTEX_LOCK();
+    if(uart->queue != NULL) {
+        uint8_t c;
+        while(xQueueReceive(uart->queue, &c, 0));
+        vQueueDelete(uart->queue);
+        uart->queue = xQueueCreate(new_size, sizeof(uint8_t));
+        if(uart->queue == NULL) {
+            return NULL;
+        }
+    }
+    UART_MUTEX_UNLOCK();
+
+    return new_size;
+}
+
 uint32_t uartAvailable(uart_t* uart)
 {
     if(uart == NULL || uart->queue == NULL) {

cores/esp32/esp32-hal-uart.h

@@ -67,6 +67,8 @@ void uartFlush(uart_t* uart);
 void uartSetBaudRate(uart_t* uart, uint32_t baud_rate);
 uint32_t uartGetBaudRate(uart_t* uart);
 
+size_t uartResizeRxBuffer(uart_t* uart, size_t new_size);
+
 void uartSetDebug(uart_t* uart);
 int uartGetDebug();