Seeed WioTerminal support (#1124)

* machine/wioterminal: add support for wioterminal board

src/machine/board_wioterminal_baremetal.go

@@ -0,0 +1,67 @@
+// +build sam,atsamd51,wioterminal
+
+package machine
+
+import (
+	"device/sam"
+	"runtime/interrupt"
+)
+
+var (
+	UART1 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM2_USART_INT,
+		SERCOM: 2,
+	}
+
+	// RTL8720D
+	UART2 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM1_USART_INT,
+		SERCOM: 1,
+	}
+)
+
+func init() {
+	UART1.Interrupt = interrupt.New(sam.IRQ_SERCOM2_2, UART1.handleInterrupt)
+	UART2.Interrupt = interrupt.New(sam.IRQ_SERCOM1_2, UART2.handleInterrupt)
+}
+
+// I2C on the Wio Terminal
+var (
+	I2C0 = I2C{
+		Bus:    sam.SERCOM4_I2CM,
+		SERCOM: 4,
+	}
+
+	I2C1 = I2C{
+		Bus:    sam.SERCOM4_I2CM,
+		SERCOM: 4,
+	}
+)
+
+// SPI on the Wio Terminal
+var (
+	SPI0 = SPI{
+		Bus:    sam.SERCOM5_SPIM,
+		SERCOM: 5,
+	}
+
+	// RTL8720D
+	SPI1 = SPI{
+		Bus:    sam.SERCOM0_SPIM,
+		SERCOM: 0,
+	}
+
+	// SD
+	SPI2 = SPI{
+		Bus:    sam.SERCOM6_SPIM,
+		SERCOM: 6,
+	}
+
+	// LCD
+	SPI3 = SPI{
+		Bus:    sam.SERCOM7_SPIM,
+		SERCOM: 7,
+	}
+)