Add board support for Adafruit Grand Central M4 (SAMD51) (#1714)

machine/grandcentral-m4: implementation for Adafruit Grand Central M4 board.

src/machine/board_grandcentral-m4_baremetal.go

@@ -0,0 +1,63 @@
+// +build grandcentral_m4
+
+package machine
+
+import (
+	"device/sam"
+	"runtime/interrupt"
+)
+
+func init() {
+	UART1.Interrupt = interrupt.New(sam.IRQ_SERCOM0_2, UART1.handleInterrupt)
+	UART2.Interrupt = interrupt.New(sam.IRQ_SERCOM4_2, UART2.handleInterrupt)
+	UART3.Interrupt = interrupt.New(sam.IRQ_SERCOM1_2, UART3.handleInterrupt)
+	UART4.Interrupt = interrupt.New(sam.IRQ_SERCOM5_2, UART4.handleInterrupt)
+}
+
+// UART on the Grand Central M4
+var (
+	UART1 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM0_USART_INT,
+		SERCOM: 0,
+	}
+	UART2 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM4_USART_INT,
+		SERCOM: 4,
+	}
+	UART3 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM1_USART_INT,
+		SERCOM: 1,
+	}
+	UART4 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM5_USART_INT,
+		SERCOM: 5,
+	}
+)
+
+// I2C on the Grand Central M4
+var (
+	I2C0 = I2C{
+		Bus:    sam.SERCOM3_I2CM,
+		SERCOM: 3,
+	}
+	I2C1 = I2C{
+		Bus:    sam.SERCOM6_I2CM,
+		SERCOM: 6,
+	}
+)
+
+// SPI on the Grand Central M4
+var (
+	SPI0 = SPI{
+		Bus:    sam.SERCOM7_SPIM,
+		SERCOM: 7,
+	}
+	SPI1 = SPI{ // SD card
+		Bus:    sam.SERCOM2_SPIM,
+		SERCOM: 2,
+	}
+)