Add nrf52840-mdk-usb-dongle target (#1654)

machine/nrf52840: add support for nrf52840-mdk-usb-dongle target

src/machine/board_nrf52840-mdk-usb-dongle.go

@@ -0,0 +1,53 @@
+// +build nrf52840_mdk_usb_dongle
+
+package machine
+
+const HasLowFrequencyCrystal = true
+
+// LEDs on the nrf52840-mdk-usb-dongle
+const (
+	LED       Pin = LED_GREEN
+	LED_GREEN Pin = 22
+	LED_RED   Pin = 23
+	LED_BLUE  Pin = 24
+)
+
+// RESET/USR button, depending on value of PSELRESET UICR register
+const (
+	BUTTON Pin = 18
+)
+
+// UART pins
+const (
+	UART_TX_PIN Pin = NoPin
+	UART_RX_PIN Pin = NoPin
+)
+
+// UART0 is the USB device
+var (
+	UART0 = USB
+)
+
+// I2C pins (unused)
+const (
+	SDA_PIN = NoPin
+	SCL_PIN = NoPin
+)
+
+// SPI pins (unused)
+const (
+	SPI0_SCK_PIN = NoPin
+	SPI0_SDO_PIN = NoPin
+	SPI0_SDI_PIN = NoPin
+)
+
+// USB CDC identifiers
+const (
+	usb_STRING_PRODUCT      = "Makerdiary nRF52840 MDK USB Dongle"
+	usb_STRING_MANUFACTURER = "Makerdiary"
+)
+
+var (
+	usb_VID uint16 = 0x1915
+	usb_PID uint16 = 0xCAFE
+)

src/machine/board_nrf52840-mdk.go

@@ -38,7 +38,7 @@ const (
 
 // USB CDC identifiers
 const (
-	usb_STRING_PRODUCT      = "Makerdiary nRF52840 MDK USB Dongle"
+	usb_STRING_PRODUCT      = "Makerdiary nRF52840 MDK"
 	usb_STRING_MANUFACTURER = "Makerdiary"
 )