diff --git a/usb/config.go b/usb/config.go
index 41142ac..b36c72c 100644
--- a/usb/config.go
+++ b/usb/config.go
@@ -27,6 +27,8 @@ type EndpointInfo struct {
 	// Number represents the endpoint number. Note that the endpoint number is different from the
 	// address field in the descriptor - address 0x82 means endpoint number 2,
 	// with endpoint direction IN.
+	// The device can have up to two endpoints with the same number but with
+	// different directions.
 	Number uint8
 	// Direction defines whether the data is flowing IN or OUT from the host perspective.
 	Direction EndpointDirection
@@ -44,9 +46,9 @@ type EndpointInfo struct {
 	UsageType UsageType
 }
 
-func (e EndpointInfo) addr() uint8 {
-	addr := e.Number
-	if e.Direction == EndpointDirectionIn {
+func endpointAddr(n uint8, d EndpointDirection) uint8 {
+	addr := n
+	if d == EndpointDirectionIn {
 		addr |= 0x80
 	}
 	return addr
@@ -55,7 +57,7 @@ func (e EndpointInfo) addr() uint8 {
 // String returns the human-readable description of the endpoint.
 func (e EndpointInfo) String() string {
 	ret := make([]string, 0, 3)
-	ret = append(ret, fmt.Sprintf("Endpoint #%d %s (address 0x%02x) %s", e.Number, e.Direction, e.addr(), e.TransferType))
+	ret = append(ret, fmt.Sprintf("Endpoint #%d %s (address 0x%02x) %s", e.Number, e.Direction, endpointAddr(e.Number, e.Direction), e.TransferType))
 	switch e.TransferType {
 	case TransferTypeIsochronous:
 		ret = append(ret, fmt.Sprintf("- %s %s", e.IsoSyncType, e.UsageType))
diff --git a/usb/device.go b/usb/device.go
index 5937dde..da90086 100644
--- a/usb/device.go
+++ b/usb/device.go
@@ -92,7 +92,7 @@ func (d *Device) Close() error {
 	return nil
 }
 
-func (d *Device) OpenEndpoint(epNum, cfgNum, ifNum, setNum uint8) (*Endpoint, error) {
+func (d *Device) OpenEndpoint(epAddr, cfgNum, ifNum, setNum uint8) (*Endpoint, error) {
 	var cfg *ConfigInfo
 	for _, c := range d.Configs {
 		if c.Config == cfgNum {
@@ -102,7 +102,7 @@ func (d *Device) OpenEndpoint(epNum, cfgNum, ifNum, setNum uint8) (*Endpoint, er
 		}
 	}
 	if cfg == nil {
-		return nil, fmt.Errorf("usb: unknown configuration %02x", cfgNum)
+		return nil, fmt.Errorf("usb: unknown configuration 0x%02x", cfgNum)
 	}
 
 	var intf *InterfaceInfo
@@ -114,7 +114,7 @@ func (d *Device) OpenEndpoint(epNum, cfgNum, ifNum, setNum uint8) (*Endpoint, er
 		}
 	}
 	if intf == nil {
-		return nil, fmt.Errorf("usb: unknown interface %02x", ifNum)
+		return nil, fmt.Errorf("usb: unknown interface 0x%02x", ifNum)
 	}
 
 	var setAlternate bool
@@ -127,18 +127,18 @@ func (d *Device) OpenEndpoint(epNum, cfgNum, ifNum, setNum uint8) (*Endpoint, er
 		}
 	}
 	if ifs == nil {
-		return nil, fmt.Errorf("usb: unknown setup %02x", setNum)
+		return nil, fmt.Errorf("usb: unknown setup 0x%02x", setNum)
 	}
 
 	var ep *EndpointInfo
 	for _, e := range ifs.Endpoints {
-		if e.Number == epNum {
-			debug.Printf("found ep %02x in %#v\n", epNum, *ifs)
+		if endpointAddr(e.Number, e.Direction) == epAddr {
+			debug.Printf("found ep 0x%02x %s in %#v\n", e.Number, e.Direction, *ifs)
 			ep = &e
 		}
 	}
 	if ep == nil {
-		return nil, fmt.Errorf("usb: unknown endpoint %02x", epNum)
+		return nil, fmt.Errorf("usb: didn't find endpoint address 0x%02x", epAddr)
 	}
 
 	end := newEndpoint(d.handle, *ifs, *ep, d.ReadTimeout, d.WriteTimeout)
diff --git a/usb/endpoint_test.go b/usb/endpoint_test.go
index bda4115..cda549c 100644
--- a/usb/endpoint_test.go
+++ b/usb/endpoint_test.go
@@ -120,7 +120,7 @@ func TestOpenEndpoint(t *testing.T) {
 	if err != nil {
 		t.Fatalf("OpenDeviceWithVidPid(0x8888, 0x0002): got error %v, want nil", err)
 	}
-	got, err := dev.OpenEndpoint(6, 1, 1, 2)
+	got, err := dev.OpenEndpoint(0x86, 1, 1, 2)
 	if err != nil {
 		t.Fatalf("OpenEndpoint(cfg=1, if=1, alt=2, ep=0x86): got error %v, want nil", err)
 	}
diff --git a/usb/libusb.go b/usb/libusb.go
index 142f0b8..e6b2ccb 100644
--- a/usb/libusb.go
+++ b/usb/libusb.go
@@ -374,7 +374,7 @@ func (libusbImpl) alloc(d *libusbDevHandle, ep *EndpointInfo, timeout time.Durat
 		return nil, fmt.Errorf("libusb_alloc_transfer(%d) failed", isoPackets)
 	}
 	xfer.dev_handle = (*C.libusb_device_handle)(d)
-	xfer.endpoint = C.uchar(ep.addr())
+	xfer.endpoint = C.uchar(endpointAddr(ep.Number, ep.Direction))
 	xfer.timeout = C.uint(timeout / time.Millisecond)
 	xfer._type = C.uchar(ep.TransferType)
 	xfer.num_iso_packets = C.int(isoPackets)