Some Serial object fixes...

cores/arduino/zephyrSerial.cpp

@@ -66,6 +66,10 @@ void arduino::ZephyrSerial::begin(unsigned long baud, uint16_t conf)
 
 	uart_configure(uart, &config);
 	uart_irq_callback_user_data_set(uart, arduino::ZephyrSerial::IrqDispatch, this);
+	k_sem_take(&rx.sem, K_FOREVER);
+	ring_buf_reset(&rx.ringbuf);
+	k_sem_give(&rx.sem);
+
 	uart_irq_rx_enable(uart);
 }
 
@@ -126,26 +130,37 @@ int arduino::ZephyrSerial::available()
 	return ret;
 }
 
+int arduino::ZephyrSerial::availableForWrite()
+{
+	int ret;
+
+	k_sem_take(&rx.sem, K_FOREVER);
+	ret = ring_buf_space_get(&rx.ringbuf);
+	k_sem_give(&rx.sem);
+
+	return ret;
+}
+
 int arduino::ZephyrSerial::peek()
 {
 	uint8_t data;
 
 	k_sem_take(&rx.sem, K_FOREVER);
-	ring_buf_peek(&rx.ringbuf, &data, 1);
+	uint32_t cb_ret = ring_buf_peek(&rx.ringbuf, &data, 1);
 	k_sem_give(&rx.sem);
 
-	return data;
+	return cb_ret? data : -1;
 }
 
 int arduino::ZephyrSerial::read()
 {
 	uint8_t data;
 
 	k_sem_take(&rx.sem, K_FOREVER);
-	ring_buf_get(&rx.ringbuf, &data, 1);
+	uint32_t cb_ret = ring_buf_get(&rx.ringbuf, &data, 1);
 	k_sem_give(&rx.sem);
 
-	return data;
+	return cb_ret? data : -1;
 }
 
 size_t arduino::ZephyrSerial::write(const uint8_t *buffer, size_t size)
@@ -174,6 +189,16 @@ size_t arduino::ZephyrSerial::write(const uint8_t *buffer, size_t size)
 	return size;
 }
 
+void arduino::ZephyrSerial::flush() {
+	while (ring_buf_size_get(&tx.ringbuf) > 0) {
+		k_yield();
+	}
+	while (uart_irq_tx_complete(uart) == 0){
+		k_yield();
+	}
+}
+
+
 #if DT_NODE_HAS_PROP(DT_PATH(zephyr_user), serials)
 #if !DT_NODE_HAS_PROP(DT_PATH(zephyr_user), cdc_acm)
 // If CDC USB, use that object as Serial (and SerialUSB)

cores/arduino/zephyrSerial.h

@@ -14,8 +14,8 @@ namespace arduino {
 class ZephyrSerialStub : public HardwareSerial
 {
 public:
-	void begin(unsigned long baudRate) { }
-	void begin(unsigned long baudrate, uint16_t config) { }
+	void begin(__attribute__((unused)) unsigned long baudRate) { }
+	void begin(__attribute__((unused)) unsigned long baudrate, __attribute__((unused)) uint16_t config) { }
 	void end() { }
 	int available() { return 0; }
 	int peek() { return 0; }
@@ -51,16 +51,13 @@ class ZephyrSerial : public HardwareSerial
 	ZephyrSerial(const struct device *dev) : uart(dev) { }
 	void begin(unsigned long baudrate, uint16_t config);
 	void begin(unsigned long baudrate) { begin(baudrate, SERIAL_8N1); }
-	void flush() {
-		while (ring_buf_size_get(&tx.ringbuf) > 0) {
-			k_yield();
-		}
-	}
+	void flush();
 	void end() { }
 	size_t write(const uint8_t *buffer, size_t size);
 	size_t write(const uint8_t data) { return write(&data, 1); }
 	using Print::write; // pull in write(str) and write(buf, size) from Print
 	int available();
+  	int availableForWrite();
 	int peek();
 	int read();
 

loader/boards/arduino_giga_r1_m7.overlay

@@ -9,6 +9,20 @@
 	status = "okay";
 };
 
+&usart2 {
+	status = "okay";
+	pinctrl-0 = <&usart2_tx_pd5 &usart2_rx_pd6>;
+	pinctrl-names = "default";
+	current-speed = <115200>;
+};
+
+&uart4 {
+	status = "okay";
+	pinctrl-0 = <&uart4_tx_ph13 &uart4_rx_pi9>;
+	pinctrl-names = "default";
+	current-speed = <115200>;
+};
+
 &usart6 {
 	status = "okay";
 };
@@ -407,7 +421,7 @@
 					<&gpioa 4 0>,
 					<&gpioa 5 0>;
 
-		serials = <&cdc_acm_uart0>, <&usart1>, <&usart6>;
+		serials = <&cdc_acm_uart0>, <&usart1>, <&usart2>, <&uart4>, <&usart6>;
 		cdc-acm = <&cdc_acm_uart0>;
 		i2cs = <&i2c4>;
 		spis = <&spi1>, <&spi5>;