diff --git a/src/machine/machine_nrf52840.go b/src/machine/machine_nrf52840.go
index c30933ba4..c858355fd 100644
--- a/src/machine/machine_nrf52840.go
+++ b/src/machine/machine_nrf52840.go
@@ -110,3 +110,7 @@ func eraseBlockSize() int64 {
 }
 
 const spiMaxBufferSize = 0xffff // from the datasheet: TXD.MAXCNT and RXD.MAXCNT
+
+// ADC instance for the VDDH input pin. This pin is typically connected to USB
+// input voltage (~5V) or directly to a battery.
+var ADC_VDDH = ADC{adcVDDHPin}
diff --git a/src/machine/machine_nrf52xxx.go b/src/machine/machine_nrf52xxx.go
index 15e7a577c..6fa267e7b 100644
--- a/src/machine/machine_nrf52xxx.go
+++ b/src/machine/machine_nrf52xxx.go
@@ -12,6 +12,8 @@ func CPUFrequency() uint32 {
 	return 64000000
 }
 
+var adcVDDHPin = Pin(254) // special pin number for VDDH on the nrf52840
+
 // InitADC initializes the registers needed for ADC.
 func InitADC() {
 	// Enable ADC.
@@ -136,6 +138,12 @@ func (a *ADC) Get() uint16 {
 		adcPin = nrf.SAADC_CH_PSELP_PSELP_AnalogInput6
 	case 31:
 		adcPin = nrf.SAADC_CH_PSELP_PSELP_AnalogInput7
+	case adcVDDHPin:
+		if Device == "nrf52840" {
+			adcPin = 0x0D // VDDHDIV5 on the nrf52840
+		} else {
+			return 0
+		}
 	default:
 		return 0
 	}