nrf52840: generic board support (#4121)

machine/nrf52840: generic board support

src/machine/board_nrf52840_generic.go

@@ -0,0 +1,25 @@
+//go:build nrf52840 && nrf52840_generic
+
+package machine
+
+var (
+	LED          = NoPin
+	SDA_PIN      = NoPin
+	SCL_PIN      = NoPin
+	UART_TX_PIN  = NoPin
+	UART_RX_PIN  = NoPin
+	SPI0_SCK_PIN = NoPin
+	SPI0_SDO_PIN = NoPin
+	SPI0_SDI_PIN = NoPin
+
+	// https://pid.codes/org/TinyGo/
+	usb_VID uint16 = 0x1209
+	usb_PID uint16 = 0x9090
+
+	usb_STRING_MANUFACTURER = "TinyGo"
+	usb_STRING_PRODUCT      = "nRF52840 Generic board"
+)
+
+var (
+	DefaultUART = UART0
+)

src/machine/machine_nrf52840_lfxtal_false.go

@@ -0,0 +1,5 @@
+//go:build nrf52840 && nrf52840_lfxtal_false
+
+package machine
+
+const HasLowFrequencyCrystal = false

src/machine/machine_nrf52840_lfxtal_true.go

@@ -0,0 +1,5 @@
+//go:build nrf52840 && ((nrf52840_generic && !nrf52840_lfxtal_false) || nrf52840_lfxtal_true)
+
+package machine
+
+const HasLowFrequencyCrystal = true