feat: add usb msc support for nrf52840

Author: mikesmitty

src/machine/machine_nrf52840_usb.go

@@ -379,3 +379,69 @@ func ReceiveUSBControlPacket() ([cdcLineInfoSize]byte, error) {
 
 	return b, nil
 }
+
+// Set the USB endpoint Packet ID to DATA0 or DATA1.
+// In endpoints must have bit 7 (0x80) set.
+func setEPDataPID(ep uint32, dataOne bool) {
+	val := ep
+	if dataOne {
+		val |= USBD_DTOGGLE_VALUE_Data1 << USBD_DTOGGLE_VALUE_Pos
+	} else {
+		val |= USBD_DTOGGLE_VALUE_Data0 << USBD_DTOGGLE_VALUE_Pos
+	}
+	nrf.USBD.DTOGGLE.Set(val)
+}
+
+// Set ENDPOINT_HALT/stall status on a USB IN endpoint.
+func (dev *USBDevice) SetStallEPIn(ep uint32) {
+	if ep&0x7F == 0 {
+		nrf.USBD.TASKS_EP0STALL.Set(1)
+	} else if ep&0x7F < NumberOfUSBEndpoints {
+		//     Stall   In     Endpoint
+		val := 0x100 | 0x80 | ep
+		nrf.USBD.EPSTALL.Set(val)
+	}
+}
+
+// Set ENDPOINT_HALT/stall status on a USB OUT endpoint.
+func (dev *USBDevice) SetStallEPOut(ep uint32) {
+	if ep == 0 {
+		nrf.USBD.TASKS_EP0STALL.Set(1)
+	} else if ep < NumberOfUSBEndpoints {
+		//     Stall   Out    Endpoint
+		val := 0x100 | 0x00 | ep
+		nrf.USBD.EPSTALL.Set(val)
+	}
+}
+
+// Clear the ENDPOINT_HALT/stall on a USB IN endpoint.
+func (dev *USBDevice) ClearStallEPIn(ep uint32) {
+	if ep&0x7F == 0 {
+		nrf.USBD.TASKS_EP0STALL.Set(0)
+	} else if ep&0x7F < NumberOfUSBEndpoints {
+		// Reset the endpoint data PID to DATA0
+		ep |= 0x80 // Set endpoint direction bit
+		setEPDataPID(ep, false)
+
+		//  No-stall   In     Endpoint
+		val := 0x000 | 0x80 | ep
+		nrf.USBD.EPSTALL.Set(val)
+	}
+}
+
+// Clear the ENDPOINT_HALT/stall on a USB OUT endpoint.
+func (dev *USBDevice) ClearStallEPOut(ep uint32) {
+	if ep == 0 {
+		nrf.USBD.TASKS_EP0STALL.Set(0)
+	} else if ep < NumberOfUSBEndpoints {
+		// Reset the endpoint data PID to DATA0
+		setEPDataPID(ep, false)
+
+		//  No-stall   Out    Endpoint
+		val := 0x000 | 0x00 | ep
+		nrf.USBD.EPSTALL.Set(val)
+
+		// Write a value to the SIZE register to allow nRF to ACK/accept data
+		nrf.USBD.SIZE.EPOUT[ep].Set(0)
+	}
+}