zephyrSerial: export ARDUINO_ROUTER_SERIAL for Arduino_RouterBridge

If the board has an 'arduino,router-serial' node, then the functionality
of the 'Serial' object is actually provided by the 'Monitor' object in
the Arduino_RouterBridge library.

Define the property for the UNO Q board and make sure the library is
always included in every sketch so that the 'Serial' object is properly
defined. A stub header is provided in the 'libraries/stubs' folder to
handle the case of the library not being installed, so that the core can
be used without requiring the installation of the libray.

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>

Author: pillo79

cores/arduino/zephyrSerial.h

@@ -146,6 +146,17 @@ class ZephyrSerial : public HardwareSerial {
 #endif
 #endif
 
+#if DT_NODE_HAS_PROP(DT_PATH(zephyr_user), arduino_router_serial)
+/* If the board has an arduino,router-serial node, and the currently used
+ * library has the support, then the 'Serial' object is actually the same as
+ * the Monitor object in the Arduino_RouterBridge library.
+ */
+#define ZARD_SKIP_FIRST_SERIAL              1
+#define ZARD_FIRST_SERIAL_IS_ARDUINO_ROUTER 1
+#define ARDUINO_ROUTER_PHANDLE              DT_PROP(DT_PATH(zephyr_user), arduino_router_serial)
+#define ARDUINO_ROUTER_SERIAL               ZARD_SERIAL_NAME(ZARD_SERIAL_INDEXOF(ARDUINO_ROUTER_PHANDLE))
+#endif
+
 /* Name of a Serial object for a given index. */
 #define ZARD_SERIAL_NAME(n) CONCAT(Serial, ZARD_SERIAL_STEM(n))
 

libraries/stubs/Arduino_RouterBridge.h

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) Arduino s.r.l. and/or its affiliated companies
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+/*
+ * This is just a placeholder to handle the case of the Arduino_RouterBridge
+ * library NOT being installed. If this file is chosen, the actual library is
+ * missing and the user needs to be warned about it.
+ */
+
+#error                                                                                             \
+	"Please install the Arduino_RouterBridge library from the Library Manager for proper Serial support on this board."

variants/arduino_uno_q_stm32u585xx/arduino_uno_q_stm32u585xx.overlay

@@ -328,6 +328,7 @@
 					<&gpioc 1 0>,
 					<&gpioc 0 0>;
 
+		arduino,router-serial = <&lpuart1>; /* 'Serial' is provided by the Monitor */
 		serials = <&usart1>, <&lpuart1>;
 		cans = <&fdcan1>;
 		i2cs = <&i2c2>, <&i2c4>, <&i2c3>;

variants/arduino_uno_q_stm32u585xx/postvariant.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) Arduino s.r.l. and/or its affiliated companies
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#pragma once
+
+/* This dance is necessary to force the inclusion of "Arduino_RouterBridge.h"
+ * during the library discovery phase, so that the library include path is
+ * added to the sketch build process.
+ *
+ * This will "discover" the stub in the libraries/stubs/ folder if the library
+ * is not installed, and the actual header if it is.
+ */
+
+#if ARDUINO_LIBRARY_DISCOVERY_PHASE
+#include "Arduino_RouterBridge.h"
+#else
+#if __has_include("Arduino_RouterBridge.h")
+#include "Arduino_RouterBridge.h"
+#endif
+#endif

variants/arduino_uno_q_stm32u585xx/variant.h

@@ -1,9 +1,20 @@
 /*
  * Copyright (c) 2022 Dhruva Gole
+ * Copyright (c) Arduino s.r.l. and/or its affiliated companies
  *
  * SPDX-License-Identifier: Apache-2.0
  */
 
+#if !ARDUINO_LIBRARY_DISCOVERY_PHASE
+#if __has_include("Arduino_RouterBridge.h")
+#if __has_include("routerbridge_provides_serial.h")
+#define ARDUINO_ROUTERBRIDGE_PROVIDES_SERIAL
+#else
+#error "Please update the Arduino_RouterBridge library to the latest version to ensure Serial support on this board."
+#endif
+#endif
+#endif
+
 // TODO: correctly handle these legacy defines
 #define MOSI    0
 #define MISO    0
@@ -27,4 +38,4 @@
 
 #define LED4_R DIGITAL_PIN_GPIOS_FIND_NODE(DT_NODELABEL(led4_red))
 #define LED4_G DIGITAL_PIN_GPIOS_FIND_NODE(DT_NODELABEL(led4_green))
-#define LED4_B DIGITAL_PIN_GPIOS_FIND_NODE(DT_NODELABEL(led4_blue))
+#define LED4_B DIGITAL_PIN_GPIOS_FIND_NODE(DT_NODELABEL(led4_blue))