machine: support arduino-nano33 on play.tinygo.org

src/machine/board_arduino_nano33_baremetal.go

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+// +build sam,atsamd21,arduino_nano33
+
+package machine
+
+import "device/sam"
+
+// UART1 on the Arduino Nano 33 connects to the onboard NINA-W102 WiFi chip.
+var (
+	UART1 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM5_USART,
+		SERCOM: 5,
+	}
+)
+
+//go:export SERCOM5_IRQHandler
+func handleUART1() {
+	defaultUART1Handler()
+}
+
+// UART2 on the Arduino Nano 33 connects to the normal TX/RX pins.
+var (
+	UART2 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM3_USART,
+		SERCOM: 3,
+	}
+)
+
+//go:export SERCOM3_IRQHandler
+func handleUART2() {
+	// should reset IRQ
+	UART2.Receive(byte((UART2.Bus.DATA.Get() & 0xFF)))
+	UART2.Bus.INTFLAG.SetBits(sam.SERCOM_USART_INTFLAG_RXC)
+}
+
+// I2C on the Arduino Nano 33.
+var (
+	I2C0 = I2C{
+		Bus:    sam.SERCOM4_I2CM,
+		SERCOM: 4,
+	}
+)
+
+// SPI on the Arduino Nano 33.
+var (
+	SPI0 = SPI{
+		Bus:    sam.SERCOM0_SPI,
+		SERCOM: 0,
+	}
+)
+
+// SPI1 is connected to the NINA-W102 chip on the Arduino Nano 33.
+var (
+	SPI1 = SPI{
+		Bus:    sam.SERCOM2_SPI,
+		SERCOM: 2,
+	}
+	NINA_SPI = SPI1
+)
+
+// I2S on the Arduino Nano 33.
+var (
+	I2S0 = I2S{Bus: sam.I2S}
+)