BNO080 Driver

Revision 9:430f5302f9e1, committed 2020-11-24

Comitter:

Jamie Smith

Date:

Tue Nov 24 15:06:05 2020 -0800

Parent:

8:199c7fad233d

Commit message:

Implement BNO080Async

Changed in this revision

--- a/BNO080.cpp	Wed Nov 18 18:07:27 2020 -0800
+++ b/BNO080.cpp	Tue Nov 24 15:06:05 2020 -0800
@@ -93,7 +93,7 @@
 
 bool BNO080Base::begin()
 {
-	//Configure the BNO080 for I2C communication
+	//Configure the BNO080
 
 	_rst = 0; // Reset BNO080
 	ThisThread::sleep_for(1ms); // Min length not specified in datasheet?
@@ -159,7 +159,7 @@
 	}
 
 	// Finally, we want to interrogate the device about its model and version.
-	zeroBuffer();
+	clearSendBuffer();
 	txShtpData[0] = SHTP_REPORT_PRODUCT_ID_REQUEST; //Request the product ID and reset info
 	txShtpData[1] = 0; //Reserved
 	sendPacket(CHANNEL_CONTROL, 2);
@@ -194,7 +194,7 @@
 
 void BNO080Base::tare(bool zOnly)
 {
-	zeroBuffer();
+	clearSendBuffer();
 
  	// from SH-2 section 6.4.4.1
 	txShtpData[3] = 0; // perform tare now
@@ -216,7 +216,7 @@
 bool BNO080Base::enableCalibration(bool calibrateAccel, bool calibrateGyro, bool calibrateMag)
 {
 	// send the Configure ME Calibration command
-	zeroBuffer();
+	clearSendBuffer();
 
 	txShtpData[3] = static_cast<uint8_t>(calibrateAccel ? 1 : 0);
 	txShtpData[4] = static_cast<uint8_t>(calibrateGyro ? 1 : 0);
@@ -259,7 +259,7 @@
 
 bool BNO080Base::saveCalibration()
 {
-	zeroBuffer();
+	clearSendBuffer();
 
 	// no arguments
 	sendCommand(COMMAND_SAVE_DCD);
@@ -295,7 +295,7 @@
 
 void BNO080Base::setSensorOrientation(Quaternion orientation)
 {
-	zeroBuffer();
+	clearSendBuffer();
 
 	// convert floats to Q
 	int16_t Q_x = floatToQ(orientation.x(), ORIENTATION_QUAT_Q_POINT);
@@ -915,7 +915,7 @@
 bool BNO080Base::readFRSRecord(uint16_t recordID, uint32_t* readBuffer, uint16_t readLength)
 {
 	// send initial read request
-	zeroBuffer();
+	clearSendBuffer();
 
 	txShtpData[0] = SHTP_REPORT_FRS_READ_REQUEST;
 	// read offset of 0 -> start at the start of the record
@@ -1024,7 +1024,7 @@
 bool BNO080Base::writeFRSRecord(uint16_t recordID, uint32_t* buffer, uint16_t length)
 {
 	// send initial write request, which tells the chip where we're writing
-	zeroBuffer();
+	clearSendBuffer();
 
 	txShtpData[0] = SHTP_REPORT_FRS_WRITE_REQUEST;
 	// length to write (must be <= record length)
@@ -1057,7 +1057,7 @@
 	for(uint16_t wordIndex = 0; wordIndex < length; wordIndex += 2)
 	{
 		// send packet containing 2 words
-		zeroBuffer();
+		clearSendBuffer();
 		txShtpData[0] = SHTP_REPORT_FRS_WRITE_DATA;
 
 		// offset to write at
@@ -1214,7 +1214,7 @@
 }
 
 
-void BNO080Base::zeroBuffer()
+void BNO080Base::clearSendBuffer()
 {
 	memset(txPacketBuffer, 0, SHTP_HEADER_SIZE + SHTP_MAX_TX_PACKET_SIZE);
 }
@@ -1548,7 +1548,7 @@
 
 	// send packet to IMU.
 	// This also might receive the first part of another packet, which there is no way to avoid.
-	_spiPort.write(reinterpret_cast<char*>(txPacketBuffer), totalLength, reinterpret_cast<char*>(rxPacketBuffer), totalLength);
+	spiTransferAndWait(txPacketBuffer, totalLength, rxPacketBuffer, totalLength);
 
 	if(rxShtpHeader[0] == 0 && rxShtpHeader[0] == 0)
 	{
@@ -1587,8 +1587,8 @@
 
 	}
 
-	// read the header bytes first
-	_spiPort.write(nullptr, 0, reinterpret_cast<char *>(rxPacketBuffer), SHTP_HEADER_SIZE);
+	// read the header bytes first.
+	spiTransferAndWait(nullptr, 0, rxPacketBuffer, SHTP_HEADER_SIZE);
 
 	// now read the data
 	return receiveCompletePacket(SHTP_HEADER_SIZE, timeout);
@@ -1655,7 +1655,7 @@
 	if(bytesRead == SHTP_HEADER_SIZE)
 	{
 		// just read the entire packet into the buffer
-		_spiPort.write(nullptr, 0, reinterpret_cast<char*>(rxPacketBuffer), totalLength);
+		spiTransferAndWait(nullptr, 0, rxPacketBuffer, totalLength);
 	}
 	else
 	{
@@ -1663,7 +1663,7 @@
 		size_t receiveLength = SHTP_HEADER_SIZE + (totalLength - bytesRead);
 
 		// read remaining bytes into the data buffer starting at the next byte
-		_spiPort.write(nullptr, 0, reinterpret_cast<char*>(rxPacketBuffer) + bytesRead, receiveLength);
+		spiTransferAndWait(nullptr, 0, rxPacketBuffer + bytesRead, receiveLength);
 
 		// erase the new header we just read, leaving only the data as a contiguous block
 		std::memmove(rxPacketBuffer + bytesRead, rxPacketBuffer + bytesRead + SHTP_HEADER_SIZE, receiveLength - SHTP_HEADER_SIZE);
@@ -1678,4 +1678,28 @@
 
 	// done!
 	return true;
-}
\ No newline at end of file
+}
+
+#if USE_ASYNC_SPI
+
+void BNO080SPI::spiTransferAndWait(const uint8_t *tx_buffer, int tx_length, uint8_t *rx_buffer, int rx_length)
+{
+	_spiPort.transfer(tx_buffer, tx_length, rx_buffer, rx_length,
+					  callback(this, &BNO080SPI::onSPITransferComplete),
+					  SPI_EVENT_COMPLETE | SPI_EVENT_ERROR);
+
+	uint32_t waitResult = spiCompleteFlag.wait_any(SPI_EVENT_ALL);
+	if(!(waitResult & SPI_EVENT_COMPLETE))
+	{
+		// at least let the user know the error happened...
+		_debugPort->printf("BNO Async SPI Error %" PRIu32 "\n", waitResult);
+	}
+
+}
+
+void BNO080SPI::onSPITransferComplete(int event)
+{
+	spiCompleteFlag.set(event);
+}
+
+#endif
\ No newline at end of file

--- a/BNO080.h	Wed Nov 18 18:07:27 2020 -0800
+++ b/BNO080.h	Tue Nov 24 15:06:05 2020 -0800
@@ -30,6 +30,17 @@
 // useful define when working with orientation quaternions
 #define SQRT_2 1.414213562f
 
+// Enable this to enable experimental support for Mbed's asynchronous SPI transfer API.
+// This will allow your processor to do other things while long SPI transfers are taking place
+// (and this IMU can end up transferring hundreds of bytes per packet, so this is useful).
+// To get this to work, you may need to use a slower clock rate (<1MHz on the STM32F429ZI I tested).
+// You also will need to edit Mbed OS code in order to use 0x00 as the SPI fill character for
+// asynchronous transfers (the API currently only allows changing this for synchronous transfers)
+// (I had to edit the SPI_FILL_CHAR constant in stm_spi_api.c).
+#define USE_ASYNC_SPI 0
+
+// Note: I filed a bug about the SPI fill char issue: https://github.com/ARMmbed/mbed-os/issues/13941
+
 /**
   Class to drive the BNO080 9-axis IMU.
   
@@ -44,7 +55,9 @@
 	Stream * _debugPort;
 
 	/// Interrupt pin -- signals to the host that the IMU has data to send
-	DigitalIn _int;
+	// Note: only ever used as a digital input by BNO080.
+	// Used for interrupts by BNO080Async.
+	InterruptIn _int;
 	
 	// Reset pin -- resets IMU when held low.
 	DigitalOut _rst;
@@ -393,9 +406,11 @@
 	 *
 	 * If this function is failing, it would be a good idea to turn on BNO_DEBUG in the cpp file to get detailed output.
 	 *
+	 * Note: this function takes several hundred ms to execute, mainly due to waiting for the BNO to boot.
+	 *
 	 * @return whether or not initialization was successful
 	 */
-	bool begin();
+	virtual bool begin();
 
 	/**
 	 * Tells the IMU to use its current rotation vector as the "zero" rotation vector and to reorient
@@ -466,6 +481,18 @@
 	 * @return true if the operation succeeded, false if it failed.
  	*/
 	bool setPermanentOrientation(Quaternion orientation);
+
+	/**
+	 * No-op on synchronous driver.  For compatibility with BNO080Async
+	 */
+	virtual void lockMutex()
+	{}
+
+	/**
+	 * No-op on synchronous driver.  For compatibility with BNO080Async
+	 */
+	virtual void unlockMutex()
+	{}
     
 	// Report functions
 	//-----------------------------------------------------------------------------------------------------------------
@@ -482,7 +509,7 @@
 	 * @return True iff new data packets of any kind were received.  If you need more fine-grained data change reporting,
 	 * check out hasNewData().
 	 */
-	bool updateData();
+	virtual bool updateData();
 
 	/**
 	 * Gets the status of a report as a 2 bit number.
@@ -623,12 +650,16 @@
 	/**
 	 * Call to wait for a packet with the given parameters to come in.
 	 *
+	 * Note: on BNO080Async, the received packet data will stay in the RX buffer
+	 * until either the public IMU function that was called returns, or you
+	 * call sendPacket() or waitForPacket() again.
+	 *
 	 * @param channel Channel of the packet
 	 * @param reportID Report ID (first data byte) of the packet
 	 * @param timeout how long to wait for the packet
 	 * @return true if the packet has been received, false if it timed out
 	 */
-	bool waitForPacket(int channel, uint8_t reportID, std::chrono::milliseconds timeout = 125ms);
+	virtual bool waitForPacket(int channel, uint8_t reportID, std::chrono::milliseconds timeout = 125ms);
 
 	/**
 	 * Given a Q value, converts fixed point floating to regular floating point number.
@@ -737,9 +768,10 @@
 	void printPacket(uint8_t * buffer);
 
 	/**
-	 * Erases the current SHTP TX packet buffer
+	 * Erases the current SHTP TX packet buffer.
+	 * In BNO080Async, this blocks until the buffer is available.
 	 */
-	 void zeroBuffer();
+	 virtual void clearSendBuffer();
 
 	 /**
 	  * Loads the metadata for this report into the metadata buffer.
@@ -750,11 +782,6 @@
 
 };
 
-// TODO list:
-// - Better handling of continued packets (discard as an error)
-// - Unified TX/RX SPI comms function
-
-
 /**
  * Version of the BNO080 driver which uses the I2C interface
  */
@@ -819,6 +846,7 @@
  */
 class BNO080SPI : public BNO080Base
 {
+protected:
 	/**
 	 * I2C port object.  Provides physical layer communications with the chip.
 	 */
@@ -851,7 +879,7 @@
 	 */
 	BNO080SPI(Stream *debugPort, PinName rstPin, PinName intPin, PinName wakePin, PinName misoPin, PinName mosiPin, PinName sclkPin, PinName csPin, int spiSpeed=3000000);
 
-private:
+protected:
 
 	bool receivePacket(std::chrono::milliseconds timeout=200ms) override;
 
@@ -863,8 +891,38 @@
 	 * @return
 	 */
 	bool receiveCompletePacket(size_t bytesRead, std::chrono::milliseconds timeout=200ms);
+
+#if USE_ASYNC_SPI
+
+	/**
+	 * Start an SPI transfer and suspend the current thread until it is complete.
+	 * Used by functions in BNO080SPI.
+	 * Note: should only be called by one thread at a time.
+	 * @param tx_buffer
+	 * @param tx_length
+	 * @param rx_buffer
+	 * @param rx_length
+	 */
+	void spiTransferAndWait(const uint8_t *tx_buffer, int tx_length, uint8_t *rx_buffer, int rx_length);
+
+	// callback for finished SPI transfers
+	void onSPITransferComplete(int event);
+
+	// Signal whan an SPI transfer is complete.
+	EventFlags spiCompleteFlag;
+
+#else
+
+	/**
+	 * Start an SPI transfer and wait for it to complete.
+	 * BNO080Async swaps in a threaded implementation here.
+	 * API same as SPI::write().
+	 */
+	void spiTransferAndWait(const uint8_t *tx_buffer, int tx_length, uint8_t *rx_buffer, int rx_length)
+	{
+		_spiPort.write(reinterpret_cast<const char *>(tx_buffer), tx_length, reinterpret_cast<char *>(rx_buffer), rx_length);
+	}
+#endif
 };
 
-
-
 #endif //HAMSTER_BNO080_H

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/BNO080Async.cpp	Tue Nov 24 15:06:05 2020 -0800
@@ -0,0 +1,305 @@
+//
+// Created by jamie on 11/18/2020.
+//
+
+#include "BNO080Async.h"
+
+#include <cinttypes>
+
+#define BNO_ASYNC_DEBUG 0
+
+// event flags constants for signalling the thread
+#define EF_INTERRUPT 0b1
+#define EF_SHUTDOWN 0b10
+#define EF_RESTART 0b100
+
+void BNO080Async::threadMain()
+{
+	while(commLoop())
+	{
+		// loop forever
+	}
+}
+
+bool BNO080Async::commLoop()
+{
+	_rst = 0; // Reset BNO080
+	ThisThread::sleep_for(1ms); // Min length not specified in datasheet?
+	_rst = 1; // Bring out of reset
+
+	// wait for a falling edge (NOT just a low) on the INT pin to denote startup
+	{
+		EventFlags edgeWaitFlags;
+		_int.fall(callback([&](){edgeWaitFlags.set(1);}));
+
+		// have the RTOS wait until an edge is detected or the timeout is hit
+		uint32_t edgeWaitEvent = edgeWaitFlags.wait_any(1, (BNO080_RESET_TIMEOUT).count());
+
+		if(!edgeWaitEvent)
+		{
+			_debugPort->printf("Error: BNO080 reset timed out, chip not detected.\n");
+		}
+	}
+
+#if BNO_ASYNC_DEBUG
+	_debugPort->printf("BNO080 detected!\r\n");
+#endif
+
+	wakeupFlags.set(EF_INTERRUPT);
+
+	// configure interrupt to send the event flag
+	_int.fall(callback([&]()
+	{
+		if(!inTXRX)
+		{
+			wakeupFlags.set(EF_INTERRUPT);
+		}
+	}));
+
+	while(true)
+	{
+		uint32_t wakeupEvent = wakeupFlags.wait_any(EF_INTERRUPT | EF_SHUTDOWN | EF_RESTART);
+
+		if(wakeupEvent & EF_SHUTDOWN)
+		{
+			// shutdown thread permanently
+			return false;
+		}
+		else if(wakeupEvent & EF_RESTART)
+		{
+			// restart thread
+			return true;
+		}
+
+		// lock the mutex to handle remaining cases
+		bnoDataMutex.lock();
+
+		if(wakeupEvent & EF_INTERRUPT)
+		{
+			while(_int == 0)
+			{
+				inTXRX = true;
+
+				// send data if there is data to send.  This may also receive a packet.
+				if (dataToSend)
+				{
+					BNO080SPI::sendPacket(txPacketChannelNumber, txPacketDataLength);
+					dataToSend = false;
+				}
+				else
+				{
+					BNO080SPI::receivePacket();
+				}
+
+				inTXRX = false;
+
+				// clear the wake flag if it was set
+				_wakePin = 1;
+
+				// If the IMU wants to send us an interrupt immediately after a transaction,
+				// it will be missed due to the inTXRX block.  So, we need to keep checking _int
+				// in a loop.
+
+				// update received flag
+				dataReceived = true;
+
+				// check if this packet is being waited on.
+				if (waitingForPacket)
+				{
+					if (waitingForReportID == rxShtpData[0] && waitingForChannel == rxShtpHeader[2])
+					{
+						// unblock main thread so it can process this packet
+						waitingPacketArrived = true;
+						waitingPacketArrivedCV.notify_all();
+
+						// unlock mutex and wait until the main thread says it's OK to receive another packet
+						clearToRxNextPacket = false;
+						waitingPacketProcessedCV.wait([&]() { return clearToRxNextPacket; });
+					}
+				}
+				else
+				{
+					processPacket();
+				}
+
+				// clear the interrupt flag if it has been set because we're about to check _int anyway.
+				// Prevents spurious wakeups.
+				wakeupFlags.clear(EF_INTERRUPT);
+
+			}
+
+		}
+
+		// unlock data mutex before waiting for flags
+		bnoDataMutex.unlock();
+	}
+}
+
+bool BNO080Async::sendPacket(uint8_t channelNumber, uint8_t dataLength)
+{
+	// first make sure mutex is locked
+	if(bnoDataMutex.get_owner() != ThisThread::get_id())
+	{
+		_debugPort->printf("IMU communication function called without bnoDataMutex locked!\n");
+		return false;
+	}
+
+	// now set class variables
+	txPacketChannelNumber = channelNumber;
+	txPacketDataLength = dataLength;
+	dataToSend = true;
+
+	// signal thread to wake up by sending _wake signal (which will cause the IMU to interrupt us once ready)
+	_wakePin = 0;
+
+	return true;
+}
+
+void BNO080Async::clearSendBuffer()
+{
+	// first make sure mutex is locked
+	if(bnoDataMutex.get_owner() != ThisThread::get_id())
+	{
+		_debugPort->printf("IMU communication function called without bnoDataMutex locked!\n");
+		return;
+	}
+
+	// Check if we are trying to send a packet while another packet is still queued.
+	// Since we don't have an actual queue, just wait until the other packet is sent.
+	while(dataToSend)
+	{
+		dataSentCV.wait();
+	}
+
+	// now actually erase the buffer
+	BNO080Base::clearSendBuffer();
+}
+
+bool BNO080Async::waitForPacket(int channel, uint8_t reportID, std::chrono::milliseconds timeout)
+{
+	// first make sure mutex is locked
+	if(bnoDataMutex.get_owner() != ThisThread::get_id())
+	{
+		_debugPort->printf("IMU communication function called without bnoDataMutex locked!\n");
+		return false;
+	}
+
+	// send information to thread
+	waitingForPacket = true;
+	waitingForChannel = channel;
+	waitingForReportID = reportID;
+	waitingPacketArrived = false;
+
+	// now unlock mutex and allow thread to run and receive packets
+	waitingPacketArrivedCV.wait_for(timeout, [&]() {return waitingPacketArrived;});
+
+	if(!waitingPacketArrived)
+	{
+		_debugPort->printf("Packet wait timeout.\n");
+		return false;
+	}
+
+	// packet we are waiting for is now in the buffer.
+	waitingForPacket = false;
+
+	// Now we can unblock the comms thread and allow it to run.
+	// BUT, it can't actually start until bnoDataMutex is released.
+	// This means that the packet data is guaranteed to stay in the buffer until that mutex is released
+	// which will happen either when the main thread is done with the IMU, or on the next sendPacket() or
+	// waitForPacket() call.
+	clearToRxNextPacket = true;
+	waitingPacketProcessedCV.notify_all();
+
+	return true;
+}
+
+BNO080Async::BNO080Async(Stream *debugPort, PinName rstPin, PinName intPin, PinName wakePin, PinName misoPin,
+						 PinName mosiPin, PinName sclkPin, PinName csPin, int spiSpeed, osPriority_t threadPriority):
+ BNO080SPI(debugPort, rstPin, intPin, wakePin, misoPin, mosiPin, sclkPin, csPin, spiSpeed),
+ commThread(threadPriority),
+ dataSentCV(bnoDataMutex),
+ waitingPacketArrivedCV(bnoDataMutex),
+ waitingPacketProcessedCV(bnoDataMutex)
+{
+
+}
+
+
+bool BNO080Async::begin()
+{
+	// shut down thread if it's running
+	if(commThread.get_state() == Thread::Deleted)
+	{
+		// start thread for the first time
+		commThread.start(callback(this, &BNO080Async::threadMain));
+	}
+	else
+	{
+		// restart thread
+		wakeupFlags.set(EF_RESTART);
+	}
+
+
+	{
+		ScopedLock<Mutex> lock(bnoDataMutex);
+
+		// once the thread starts it, the BNO will send an Unsolicited Initialize response (SH-2 section 6.4.5.2), and an Executable Reset command
+		if(!waitForPacket(CHANNEL_EXECUTABLE, EXECUTABLE_REPORTID_RESET, 1s))
+		{
+			_debugPort->printf("No initialization report from BNO080.\n");
+			return false;
+		}
+		else
+		{
+#if BNO_DEBUG
+			_debugPort->printf("BNO080 reports initialization successful!\n");
+#endif
+		}
+
+		// Finally, we want to interrogate the device about its model and version.
+		clearSendBuffer();
+		txShtpData[0] = SHTP_REPORT_PRODUCT_ID_REQUEST; //Request the product ID and reset info
+		txShtpData[1] = 0; //Reserved
+		sendPacket(CHANNEL_CONTROL, 2);
+
+		waitForPacket(CHANNEL_CONTROL, SHTP_REPORT_PRODUCT_ID_RESPONSE);
+
+		if (rxShtpData[0] == SHTP_REPORT_PRODUCT_ID_RESPONSE)
+		{
+			majorSoftwareVersion = rxShtpData[2];
+			minorSoftwareVersion = rxShtpData[3];
+			patchSoftwareVersion = (rxShtpData[13] << 8) | rxShtpData[12];
+			partNumber = (rxShtpData[7] << 24) | (rxShtpData[6] << 16) | (rxShtpData[5] << 8) | rxShtpData[4];
+			buildNumber = (rxShtpData[11] << 24) | (rxShtpData[10] << 16) | (rxShtpData[9] << 8) | rxShtpData[8];
+
+#if BNO_DEBUG
+			_debugPort->printf("BNO080 reports as SW version %hhu.%hhu.%hu, build %lu, part no. %lu\n",
+						   majorSoftwareVersion, minorSoftwareVersion, patchSoftwareVersion,
+						   buildNumber, partNumber);
+#endif
+
+		}
+		else
+		{
+			_debugPort->printf("Bad response from product ID command.\n");
+			return false;
+		}
+	}
+
+
+	// successful init
+	return true;
+}
+
+bool BNO080Async::updateData()
+{
+	bool newData = dataReceived;
+	dataReceived = false;
+	return newData;
+}
+
+
+
+
+
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/BNO080Async.graphml	Tue Nov 24 15:06:05 2020 -0800
@@ -0,0 +1,269 @@
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--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/BNO080Async.h	Tue Nov 24 15:06:05 2020 -0800
@@ -0,0 +1,143 @@
+#ifndef BNO080_BNO080ASYNC_H
+#define BNO080_BNO080ASYNC_H
+
+#if MBED_CONF_RTOS_PRESENT
+
+#include <BNO080.h>
+#include <Mutex.h>
+
+/**
+ * Asynchronous version of the SPI BNO080 driver.
+ * Since the timing requirements of this driver are so different,
+ * wouldn't it be great to have a dedicated thread to handle them?
+ * This class provides exactly that, using an internal thread triggered
+ * by interrupts to connect to the BNO.
+ *
+ * Note: the internal thread is started the first time begin() is called,
+ * and is shut down when the class is destroyed.
+ */
+class BNO080Async : public BNO080SPI
+{
+public:
+	// Mutex protecting all sensor data in the driver.
+	// You must lock this while reading data and unlock it when done.
+	// While this is locked, the background thread is prevented from running.
+	Mutex bnoDataMutex;
+
+private:
+	// thread in charge of communicating with the BNO
+	Thread commThread;
+
+	// EventFlags to allow signalling the thread to wake up
+	EventFlags wakeupFlags;
+
+	// main function for the thread.
+	// Handles starting the comm loop.
+	void threadMain();
+
+	// Code loop to communicate with the BNO.
+	// Runs forever in normal operation.
+	// Returns true to request a restart.
+	// Returns false to request the thread to shutdown.
+	bool commLoop();
+
+	// flag to indicate that we have valid data to send queued in the TX buffer.
+	// Protected by bnoDataMutex.
+	bool dataToSend = false;
+
+	// data for packet to send, if above flag is true
+	uint8_t txPacketChannelNumber;
+	uint8_t txPacketDataLength;
+
+	// Condition variable signaled whenever a packet is sent.
+	ConditionVariable dataSentCV;
+
+	// flag used for updateData() return value.
+	// True if any data packets have been received since the last update.
+	bool dataReceived = false;
+
+	// true iff the thread is currently in the middle of a TX/RX operation.
+	// Causes _int interrupts (which get generated by the comms process) to be ignored.
+	bool inTXRX = false;
+
+	bool sendPacket(uint8_t channelNumber, uint8_t dataLength) override;
+
+	void clearSendBuffer() override;
+
+	// waiting for packet state info
+	bool waitingForPacket = false;
+	uint8_t waitingForChannel;
+	uint8_t waitingForReportID;
+	bool waitingPacketArrived = false;
+	bool clearToRxNextPacket = false;
+
+	ConditionVariable waitingPacketArrivedCV;
+	ConditionVariable waitingPacketProcessedCV;
+
+	bool waitForPacket(int channel, uint8_t reportID, std::chrono::milliseconds timeout = 125ms) override;
+
+public:
+	/**
+	 * Construct a BNO080Async.
+	 * This doesn't actually initialize the chip, you will need to call begin() for that.
+	 *
+	 * NOTE: while some schematics tell you to connect the BOOTN pin to the processor, this driver does not use or require it.
+	 * Just tie it to VCC per the datasheet.
+	 *
+	 * @param debugPort Serial port to write output to.  Cannot be nullptr.
+	 * @param rstPin Hardware reset pin, resets the IMU
+	 * @param intPin Hardware interrupt pin, this is used for the IMU to signal the host that it has a message to send
+	 * @param wakePin Hardware wake pin, this is used by the processor to signal the BNO to wake up and receive a message
+	 * @param misoPin SPI MISO pin
+	 * @param mosiPin SPI MOSI pin
+	 * @param sclkPin SPI SCLK pin
+	 * @param csPin SPI CS pin
+	 * @param spiSpeed SPI frequency.  The BNO's max is 3MHz.
+	 * @param threadPriority Priority to give the internal thread.  Defaults to AboveNormal so it will run whenever it can.
+	 */
+	BNO080Async(Stream *debugPort, PinName rstPin, PinName intPin, PinName wakePin, PinName misoPin, PinName mosiPin, PinName sclkPin, PinName csPin, int spiSpeed=3000000, osPriority threadPriority=osPriorityAboveNormal);
+
+	/**
+	 * Resets and connects to the IMU.  Verifies that it's connected, and reads out its version
+	 * info into the class variables above.
+	 *
+	 * Async version also starts the internal communication thread, restarting it if it's
+	 * already started.
+	 *
+	 * If this function is failing, it would be a good idea to turn on BNO_DEBUG in the cpp file to get detailed output.
+	 *
+	 * @return whether or not initialization was successful
+	 */
+	bool begin() override;
+
+	/**
+	 * In BNO080Async, there is no need to call updateData() in order to get new
+	 * results, but this call is provided for compatibility.
+	 *
+	 * It maintains its behavior of returning true iff packets have been received since the last call.
+	 * You must lock bnoDataMutex to call this.
+	 * @return
+	 */
+	bool updateData() override;
+
+	/**
+	 * Locks the data mutex.
+	 */
+	void lockMutex() override
+	{
+		bnoDataMutex.lock();
+	}
+
+	/**
+	 * Unlocks the data mutex.
+	 */
+	void unlockMutex() override
+	{
+		bnoDataMutex.unlock();
+	}
+};
+
+#endif
+
+
+#endif //MBED_CMAKE_TEST_PROJECT_BNO080ASYNC_H