machine/atsamd51: add support for ATSAMD51 processor using Adafruit ItsyBitsy-M4 board

Signed-off-by: Ron Evans <ron@hybridgroup.com>

src/machine/board_itsybitsy-m4.go

@@ -0,0 +1,83 @@
+// +build sam,atsamd51,itsybitsy_m4
+
+package machine
+
+import "device/sam"
+
+// used to reset into bootloader
+const RESET_MAGIC_VALUE = 0xf01669ef
+
+// GPIO Pins
+const (
+	D0  = PA16 // UART0 RX/PWM available
+	D1  = PA17 // UART0 TX/PWM available
+	D2  = PA07
+	D3  = PB22
+	D4  = PA14 // PWM available
+	D5  = PA15 // PWM available
+	D6  = PB02 // dotStar clock
+	D7  = PA18 // PWM available
+	D8  = PB03 // dotStar data
+	D9  = PA19 // PWM available
+	D10 = PA20 // can be used for PWM or UART1 TX
+	D11 = PA21 // can be used for PWM or UART1 RX
+	D12 = PA23 // PWM available
+	D13 = PA22 // PWM available
+)
+
+// Analog pins
+const (
+	A0 = PA02 // ADC/AIN[0]
+	A1 = PB05 // ADC/AIN[2]
+	A2 = PB08 // ADC/AIN[3]
+	A3 = PB09 // ADC/AIN[4]
+	A4 = PA04 // ADC/AIN[5]
+	A5 = PA06 // ADC/AIN[10]
+)
+
+const (
+	LED = D13
+)
+
+// UART0 aka USBCDC pins
+const (
+	USBCDC_DM_PIN = PA24
+	USBCDC_DP_PIN = PA25
+)
+
+// UART1 pins
+const (
+	UART_TX_PIN = D1
+	UART_RX_PIN = D0
+)
+
+// I2C pins
+const (
+	SDA_PIN = PA12 // SDA: SERCOM3/PAD[0]
+	SCL_PIN = PA13 // SCL: SERCOM3/PAD[1]
+)
+
+// I2C on the ItsyBitsy M4.
+var (
+	I2C0 = I2C{Bus: sam.SERCOM2_I2CM,
+		SDA:     SDA_PIN,
+		SCL:     SCL_PIN,
+		PinMode: PinSERCOM}
+)
+
+// SPI pins
+const (
+	SPI0_SCK_PIN  = PA01 // SCK: SERCOM1/PAD[1]
+	SPI0_MOSI_PIN = PA00 // MOSI: SERCOM1/PAD[0]
+	SPI0_MISO_PIN = PB23 // MISO: SERCOM1/PAD[3]
+)
+
+// SPI on the ItsyBitsy M4.
+var (
+	SPI0 = SPI{Bus: sam.SERCOM1_SPI,
+		SCK:   SPI0_SCK_PIN,
+		MOSI:  SPI0_MOSI_PIN,
+		MISO:  SPI0_MISO_PIN,
+		DOpad: spiTXPad2SCK3,
+		DIpad: sercomRXPad0}
+)