[Bug] Arturia MIDI controllers cause dropped MIDI messages

[marchingband]

I have tested 2 different Arturia MIDI controllers, the Keystep Pro, and the MiniLab. Circle USB MIDI Host driver drops messages from both.

If I press 2 notes at the same time, about 1 in 4 times, it will miss a message. These could be note on, in which case I dont get the note, or it could be note off, in which case we get a stuck note.

I have Circle git hash c243194
hardware is CM0

However if I comment out line 198 in lib/usb/usbmidihost.cpp the issue goes away.
// pURB->SetCompleteOnNAK ();

This keeps the IN request active through NAKs, so the host controller can catch the next data packet without that resubmit gap.

I also have -DNO_SDHOST -DUSE_USB_FIQ and usbboost=true set.

[marchingband]

I spoke too soon, larger chords still drop messages.
I will have to look deeper into the driver, unless you have any tips.

[rsta2]

Unfortunately it is a known problem, that some USB MIDI keyboard controllers loose keyboard events, when working with Circle and a lot of time has been spent already to solve this, but without success. Can you try to add the following option to the file cmdline.txt on the SD card, this helped in some cases: usbspeed=full

[marchingband]

Any idea why this issue does not exist in https://github.com/soyersoyer/MiniDexed.git? It also uses Circle.

[rsta2]

It exists. But as far as I know MiniDexed uses the "usbspeed=full" option as recommended in my previous comment.

[rsta2]

Have you tried the usbspeed=full option?

[marchingband]

Yes but it didn’t fix it. This FW has a lot going on. I modified some driver code and have it working now, I will try to make a PR soon and you can have a look.

…

On Mon, Jul 13, 2026 at 9:22 PM Rene Stange ***@***.***> wrote: *rsta2* left a comment (rsta2/circle#676) <#676 (comment)> Have you tried the usbspeed=full option? — Reply to this email directly, view it on GitHub <#676?email_source=notifications&email_token=AIE667GEZ4QTTLJZIWCQFDD5EWYOVA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIOJWGUZTMNJRGU3KM4TFMFZW63VGMF2XI2DPOKSWK5TFNZ2KYZTPN52GK4S7MNWGSY3L#issuecomment-4965365156>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIE667A7X4IKAGGNS5XKYK35EWYOVAVCNFSNUABEKJSXA33TNF2G64TZHMZDKNRXGY3TOMZ3JFZXG5LFHM2DONRVGQ4DCMBXGKQXMAQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[rsta2]

OK, that's great!

[rsta2]

Can I still expect a PR as a fix for this issue?

[marchingband]

I don't think it is a good PR, I just got it to the point it worked for me, using a double buffer on FIQ, but here is the diff.
Is that useful enough?

diff --git a/include/circle/usb/dwhcidevice.h b/include/circle/usb/dwhcidevice.h
index 6d28059..405e4f5 100644
--- a/include/circle/usb/dwhcidevice.h
+++ b/include/circle/usb/dwhcidevice.h
@@ -124,6 +124,7 @@ private:
 			    unsigned	    nMsTimeout);
 
 	void LogTransactionFailed (u32 nStatus);
+	void CompleteRequest (CUSBRequest *pURB);
 
 #ifndef NDEBUG
 	void DumpRegister (const char *pName, u32 nAddress);
diff --git a/include/circle/usb/usbmidihost.h b/include/circle/usb/usbmidihost.h
index 43fd89b..33773be 100644
--- a/include/circle/usb/usbmidihost.h
+++ b/include/circle/usb/usbmidihost.h
@@ -56,7 +56,9 @@ private:
 	CUSBEndpoint *m_pEndpointOut;
 
 	u16 m_usBufferSize;
-	u8 *m_pPacketBuffer;
+	static const unsigned RXBufferCount = 2;
+	u8 *m_pPacketBuffer[RXBufferCount];
+	unsigned m_nNextBuffer;
 
 	TKernelTimerHandle m_hTimer;
 };
diff --git a/include/circle/usb/usbrequest.h b/include/circle/usb/usbrequest.h
index 648c676..7923ac4 100644
--- a/include/circle/usb/usbrequest.h
+++ b/include/circle/usb/usbrequest.h
@@ -63,6 +63,10 @@ public:
 	// do not retry if request cannot be served immediately (for Bulk in only)
 	void SetCompleteOnNAK (void);
 	boolean IsCompleteOnNAK (void) const;
+
+	// complete from the primary USB interrupt path, if the host driver supports it
+	void SetCompleteImmediately (void);
+	boolean IsCompleteImmediately (void) const;
 	
 private:
 	CUSBEndpoint *m_pEndpoint;
@@ -83,6 +87,7 @@ private:
 	void *m_pCompletionContext;
 
 	boolean m_bCompleteOnNAK;
+	boolean m_bCompleteImmediately;
 
 	DECLARE_CLASS_ALLOCATOR
 };
diff --git a/lib/usb/dwhcidevice.cpp b/lib/usb/dwhcidevice.cpp
index 6d75fb1..fa2ac74 100644
--- a/lib/usb/dwhcidevice.cpp
+++ b/lib/usb/dwhcidevice.cpp
@@ -793,6 +793,29 @@ boolean CDWHCIDevice::TransferStageAsync (CUSBRequest *pURB, boolean bIn, boolea
 #ifndef USE_USB_SOF_INTR
 	StartTransaction (pStageData);
 #else
+#ifdef USB_NOSPLIT_BULK_IMMEDIATE
+	if (   CKernelOptions::Get ()->GetUSBBoost ()
+	    && !pStageData->IsSplit ()
+	    && !pStageData->IsPeriodic ())
+	{
+		nChannel = AllocateChannel ();
+		if (nChannel < m_nChannels)
+		{
+			pStageData->SetChannelNumber (nChannel);
+
+			assert (m_pStageData[nChannel] == 0);
+			m_pStageData[nChannel] = pStageData;
+
+			EnableChannelInterrupt (nChannel);
+			StartTransaction (pStageData);
+		}
+		else
+		{
+			QueueTransaction (pStageData);
+		}
+	}
+	else
+#endif
 	QueueTransaction (pStageData);
 #endif
 	
@@ -1036,11 +1059,7 @@ void CDWHCIDevice::ChannelInterruptHandler (unsigned nChannel)
 
 		FreeChannel (nChannel);
 
-#ifndef USE_USB_FIQ
-		pURB->CallCompletionRoutine ();
-#else
-		m_CompletionQueue.Enqueue (pURB);
-#endif
+		CompleteRequest (pURB);
 
 		return;
 	}
@@ -1183,11 +1202,7 @@ void CDWHCIDevice::ChannelInterruptHandler (unsigned nChannel)
 
 		FreeChannel (nChannel);
 
-#ifndef USE_USB_FIQ
-		pURB->CallCompletionRoutine ();
-#else
-		m_CompletionQueue.Enqueue (pURB);
-#endif
+		CompleteRequest (pURB);
 		break;
 
 	case StageStateStartSplit:
@@ -1208,11 +1223,7 @@ void CDWHCIDevice::ChannelInterruptHandler (unsigned nChannel)
 
 			FreeChannel (nChannel);
 
-#ifndef USE_USB_FIQ
-			pURB->CallCompletionRoutine ();
-#else
-			m_CompletionQueue.Enqueue (pURB);
-#endif
+			CompleteRequest (pURB);
 			break;
 		}
 
@@ -1258,11 +1269,7 @@ void CDWHCIDevice::ChannelInterruptHandler (unsigned nChannel)
 
 			FreeChannel (nChannel);
 
-#ifndef USE_USB_FIQ
-			pURB->CallCompletionRoutine ();
-#else
-			m_CompletionQueue.Enqueue (pURB);
-#endif
+			CompleteRequest (pURB);
 			break;
 		}
 		
@@ -1316,11 +1323,7 @@ void CDWHCIDevice::ChannelInterruptHandler (unsigned nChannel)
 
 					FreeChannel (nChannel);
 
-#ifndef USE_USB_FIQ
-					pURB->CallCompletionRoutine ();
-#else
-					m_CompletionQueue.Enqueue (pURB);
-#endif
+					CompleteRequest (pURB);
 				}
 				else
 				{
@@ -1355,11 +1358,7 @@ void CDWHCIDevice::ChannelInterruptHandler (unsigned nChannel)
 
 		FreeChannel (nChannel);
 
-#ifndef USE_USB_FIQ
-		pURB->CallCompletionRoutine ();
-#else
-		m_CompletionQueue.Enqueue (pURB);
-#endif
+		CompleteRequest (pURB);
 		break;
 
 	default:
@@ -1579,6 +1578,24 @@ void CDWHCIDevice::TimerStub (TKernelTimerHandle /* hTimer */, void *pParam, voi
 
 #endif
 
+void CDWHCIDevice::CompleteRequest (CUSBRequest *pURB)
+{
+	assert (pURB != 0);
+
+#ifndef USE_USB_FIQ
+	pURB->CallCompletionRoutine ();
+#else
+	if (pURB->IsCompleteImmediately ())
+	{
+		pURB->CallCompletionRoutine ();
+	}
+	else
+	{
+		m_CompletionQueue.Enqueue (pURB);
+	}
+#endif
+}
+
 #ifdef USE_USB_FIQ
 
 void CDWHCIDevice::InterruptHandler2 (void)
diff --git a/lib/usb/gadget/dwusbgadget.cpp b/lib/usb/gadget/dwusbgadget.cpp
index c6a3c63..022cca8 100644
--- a/lib/usb/gadget/dwusbgadget.cpp
+++ b/lib/usb/gadget/dwusbgadget.cpp
@@ -77,6 +77,7 @@ boolean CDWUSBGadget::Initialize (boolean bScanDevices)
 	    && Model != MachineModelZero
 	    && Model != MachineModelZeroW
 	    && Model != MachineModelZero2W
+	    && Model != MachineModelCM0
 	    && Model != MachineModel3APlus
 	    && Model != MachineModel4B
 	    && Model != MachineModel400)
diff --git a/lib/usb/usbmidi.cpp b/lib/usb/usbmidi.cpp
index 845d471..67d28ea 100644
--- a/lib/usb/usbmidi.cpp
+++ b/lib/usb/usbmidi.cpp
@@ -40,6 +40,51 @@ static const unsigned cin_to_length[] = {
 	0, 0, 2, 3, 3, 1, 2, 3, 3, 3, 3, 3, 2, 2, 3, 1
 };
 
+static boolean IsMIDIDataByte (u8 uchByte)
+{
+	return uchByte < 0x80;
+}
+
+static boolean IsValidEventPacket (const u8 *pPacket)
+{
+	assert (pPacket != 0);
+
+	u8 nCIN = pPacket[0] & 0x0F;
+	if (cin_to_length[nCIN] == 0)
+	{
+		return FALSE;
+	}
+
+	switch (nCIN)
+	{
+	case 0x2:	// 2-byte system common
+		return    (pPacket[1] == 0xF1 || pPacket[1] == 0xF3)
+		       && IsMIDIDataByte (pPacket[2]);
+
+	case 0x3:	// 3-byte system common
+		return    pPacket[1] == 0xF2
+		       && IsMIDIDataByte (pPacket[2])
+		       && IsMIDIDataByte (pPacket[3]);
+
+	case 0x8:	// note off
+	case 0x9:	// note on
+	case 0xA:	// poly key pressure
+	case 0xB:	// control change
+	case 0xE:	// pitch bend
+		return    (pPacket[1] >> 4) == nCIN
+		       && IsMIDIDataByte (pPacket[2])
+		       && IsMIDIDataByte (pPacket[3]);
+
+	case 0xC:	// program change
+	case 0xD:	// channel pressure
+		return    (pPacket[1] >> 4) == nCIN
+		       && IsMIDIDataByte (pPacket[2]);
+
+	default:
+		return TRUE;
+	}
+}
+
 CUSBMIDIDevice::CUSBMIDIDevice (void)
 :	m_pPacketHandler (0),
 	m_pSendEventsHandler (0),
@@ -243,7 +288,8 @@ boolean CUSBMIDIDevice::CallPacketHandler (u8 *pData, unsigned nLength)
 		// Follow the Linux driver's example and ignore packets with Cable
 		// Number == Code Index Number == 0, which some devices seem to
 		// generate as padding in spite of their status as reserved.
-		if (pPacket[0] != 0)
+		if (   pPacket[0] != 0
+		    && IsValidEventPacket (pPacket))
 		{
 			if (m_pPacketHandler != 0)
 			{
diff --git a/lib/usb/usbmidihost.cpp b/lib/usb/usbmidihost.cpp
index 1d1f19b..e2733d2 100644
--- a/lib/usb/usbmidihost.cpp
+++ b/lib/usb/usbmidihost.cpp
@@ -40,9 +40,13 @@ CUSBMIDIHostDevice::CUSBMIDIHostDevice (CUSBFunction *pFunction)
 	m_pInterface (0),
 	m_pEndpointIn (0),
 	m_pEndpointOut (0),
-	m_pPacketBuffer (0),
+	m_nNextBuffer (0),
 	m_hTimer (0)
 {
+	for (unsigned i = 0; i < RXBufferCount; i++)
+	{
+		m_pPacketBuffer[i] = 0;
+	}
 }
 
 CUSBMIDIHostDevice::~CUSBMIDIHostDevice (void)
@@ -56,8 +60,11 @@ CUSBMIDIHostDevice::~CUSBMIDIHostDevice (void)
 	delete m_pInterface;
 	m_pInterface = 0;
 
-	delete [] m_pPacketBuffer;
-	m_pPacketBuffer = 0;
+	for (unsigned i = 0; i < RXBufferCount; i++)
+	{
+		delete [] m_pPacketBuffer[i];
+		m_pPacketBuffer[i] = 0;
+	}
 
 	delete m_pEndpointIn;
 	m_pEndpointIn = 0;
@@ -123,9 +130,12 @@ boolean CUSBMIDIHostDevice::Configure (void)
 			m_usBufferSize -=   pEndpointDesc->wMaxPacketSize
 					  % CUSBMIDIDevice::EventPacketSize;
 
-			assert (m_pPacketBuffer == 0);
-			m_pPacketBuffer = new u8[m_usBufferSize];
-			assert (m_pPacketBuffer != 0);
+			for (unsigned i = 0; i < RXBufferCount; i++)
+			{
+				assert (m_pPacketBuffer[i] == 0);
+				m_pPacketBuffer[i] = new u8[m_usBufferSize];
+				assert (m_pPacketBuffer[i] != 0);
+			}
 		}
 		else							// Output EP
 		{
@@ -188,14 +198,23 @@ boolean CUSBMIDIHostDevice::SendEventsHandler (const u8 *pData, unsigned nLength
 boolean CUSBMIDIHostDevice::StartRequest (void)
 {
 	assert (m_pEndpointIn != 0);
-	assert (m_pPacketBuffer != 0);
+	assert (m_pPacketBuffer[m_nNextBuffer] != 0);
 
 	assert (m_usBufferSize > 0);
-	CUSBRequest *pURB = new CUSBRequest (m_pEndpointIn, m_pPacketBuffer, m_usBufferSize);
+	u8 *pPacketBuffer = m_pPacketBuffer[m_nNextBuffer];
+	m_nNextBuffer = (m_nNextBuffer + 1) % RXBufferCount;
+
+	CUSBRequest *pURB = new CUSBRequest (m_pEndpointIn, pPacketBuffer, m_usBufferSize);
 	assert (pURB != 0);
 	pURB->SetCompletionRoutine (CompletionStub, 0, this);
 
+#ifdef USB_MIDI_FIQ_COMPLETION
+	pURB->SetCompleteImmediately ();
+#endif
+
+#ifndef USB_MIDI_RETRY_ON_NAK
 	pURB->SetCompleteOnNAK ();	// do not retry if request cannot be served immediately
+#endif
 
 	return GetHost ()->SubmitAsyncRequest (pURB);
 }
@@ -206,14 +225,22 @@ void CUSBMIDIHostDevice::CompletionRoutine (CUSBRequest *pURB)
 	assert (m_pInterface != 0);
 
 	boolean bRestart = FALSE;
+	u8 *pPacketBuffer = static_cast<u8 *> (pURB->GetBuffer ());
+	unsigned nResultLength = pURB->GetStatus () ? pURB->GetResultLength () : 0;
 
 	if (   pURB->GetStatus () != 0
-	    && pURB->GetResultLength () % CUSBMIDIDevice::EventPacketSize == 0)
+	    && nResultLength % CUSBMIDIDevice::EventPacketSize == 0)
 	{
-		assert (m_pPacketBuffer != 0);
-
-		bRestart = m_pInterface->CallPacketHandler (m_pPacketBuffer,
-							    pURB->GetResultLength ());
+#ifdef USB_MIDI_EARLY_RESUBMIT
+		if (nResultLength > 0)
+		{
+			m_pInterface->CallPacketHandler (pPacketBuffer, nResultLength);
+			delete pURB;
+			StartRequest ();
+			return;
+		}
+#endif
+		bRestart = m_pInterface->CallPacketHandler (pPacketBuffer, nResultLength);
 	}
 	else if (   m_pInterface->GetAllSoundOffOnUSBError ()
 		 && !pURB->GetStatus ()
diff --git a/lib/usb/usbrequest.cpp b/lib/usb/usbrequest.cpp
index a3a0747..889f623 100644
--- a/lib/usb/usbrequest.cpp
+++ b/lib/usb/usbrequest.cpp
@@ -32,7 +32,8 @@ CUSBRequest::CUSBRequest (CUSBEndpoint *pEndpoint, void *pBuffer, u32 nBufLen, T
 	m_pCompletionRoutine (0),
 	m_pCompletionParam (0),
 	m_pCompletionContext (0),
-	m_bCompleteOnNAK (FALSE)
+	m_bCompleteOnNAK (FALSE),
+	m_bCompleteImmediately (FALSE)
 {
 	assert (m_pEndpoint != 0);
 	assert (m_pBuffer != 0 || m_nBufLen == 0);
@@ -156,4 +157,14 @@ boolean CUSBRequest::IsCompleteOnNAK (void) const
 	return m_bCompleteOnNAK;
 }
 
+void CUSBRequest::SetCompleteImmediately (void)
+{
+	m_bCompleteImmediately = TRUE;
+}
+
+boolean CUSBRequest::IsCompleteImmediately (void) const
+{
+	return m_bCompleteImmediately;
+}
+
 IMPLEMENT_CLASS_ALLOCATOR (CUSBRequest)

[rsta2]

Thank you for the diff! I will see, how I can integrate it.

[rsta2]

I have a question on the configuration, you are usually using. Which of the following defines are normally defined?

USB_MIDI_FIQ_COMPLETION
USB_MIDI_RETRY_ON_NAK
USB_MIDI_EARLY_RESUBMIT
USB_NOSPLIT_BULK_IMMEDIATE
USE_USB_FIQ

EDIT: USB_NOSPLIT_BULK_IMMEDIATE added

[marchingband]

All of those are defined and
cmdline.txt has usbboost=true
config.mk has DEFINE += -DNO_SDHOST -DUSE_USB_FIQ -DUSB_MIDI_RETRY_ON_NAK -DUSB_MIDI_EARLY_RESUBMIT -DUSB_NOSPLIT_BULK_IMMEDIATE -DUSB_MIDI_FIQ_COMPLETION

[rsta2]

Thanks for answering!

[rsta2]

I integrated your code into Circle, mostly as it was, but with a different method to select most of the (previously build-) options. The cmdline.txt option usbboost= has been extended and gets a bit mask as a decimal number now, where a set bit 0-3 activates one of the available options:

From doc/cmdline.txt:

The parameter is a decimal number (default 0) with the following
values or'ed together: 1 (Do not insert a delay, when no MIDI event
has been received, same as when "true" is specified), 2 (do complete
on NAK and relax the USB, when no MIDI event is available, this may
break other attached devices), 4 (restart receiving MIDI events,
before the previous received events have been processed),
8 (immediately start no-split Bulk requests without queuing, this
may break the standard USB timing).

The build option USB_MIDI_FIQ_COMPLETION still exists as before, because existing applications must be changed to be able to accept calls to the MIDI packet handler at FIQ_LEVEL, which is normally not the case.

There is also a new build option USB_MIDI_CHECK_INCOMING, which enables the validation of incoming MIDI events. Because most existing applications should do this already on their own, validating it twice would reduce performance a little bit and so it is an option now.

The modified code is currently on the branch usb-midi-boost. It would be great, if you could test it with your system, so that I know, that it works, before I merge it. Unfortunately I do not have a USB MIDI keyboard controller, which lost MIDI events before, so I cannot really test the effect of the changes. You should set the following options to enable all options as before:

In Config.mk:

DEFINE += -DUSE_USB_FIQ -DUSB_MIDI_FIQ_COMPLETION -DUSB_MIDI_CHECK_INCOMING

In cmdline.txt:

usbboost=15

[marchingband]

I will do my best to test when I have some time. It's not so straightforward for me because my circle repo is pretty dirty, and I am working from a commit from last year.
FYI any Arturia MIDI controller will test this change. Even the MINILab MKI I got on marketplace for $50