feat: double tap to reset orientation (xiao-ble)

README.md

@@ -109,8 +109,14 @@ First, you shall [flash UF2 bootloader to the board](./doc/Nano33BLE.md). You on
 Then connect the board to your computer, double-tap on button and copy `ht_nano-33-ble_xxx.uf2` file to NANO33BOOT usb drive.
 
 ## Use head tracker
-Attach the board with flashed head tracker code to your FPV goggles.  
-Place your goggles on a solid surface and power the head tracker with 2 cell battery or 5v source. I use analog adaptor bay on my DJI goggles to source 5v. 
+Attach the head tracker to your FPV goggles.  
+Power the head tracker via USB, 2 cell battery or 5v source.  
+> Hint: I personally use analog adapter bay on my DJI V1 goggles to source 5v.  
+
+### Bare
+The head tracker is usable "bare", no extra accessories needed, not even a button.  
+To reset the orientation without a button, simply **double-tap** the head tracker.  
+> Hint: When the head tracker is mounted on your goggles directly, you can just double-tap your googles in any place to reset the orientation.
 
 ### LEDs
 On start, board shall blink continuously blue, red and green/orange leds.
@@ -119,12 +125,11 @@ On start, board shall blink continuously blue, red and green/orange leds.
 - Green/orange led indicates health of the head tracker and shall slowly blink during normal operation.
 
 ### Buttons
-The head tracker records initial orientation on power up, place your goggles accordingly.  
-Optionally, a **reset orientation** button can be wired to **D2** and **GND** pins.
-Keep **reset orientation** button pressed on power up to discard calibration parameters stored in flash memory.
+The head tracker records initial orientation on power up, place your goggles accordingly or reset orientation later by double-tapping the head tracker or by using a **reset orientation** button that can be wired to **D2** and **GND** pins.  
+Keep **reset orientation** button pressed on power up to **discard calibration parameters** stored in flash memory.
 
 ### Screen
-If you have a LED 128x32 screen added you your board (via I2C), the board's bluetooth address is displayed on it. Blinking ":" symbols indicate bluetooth connection status, like blue led. Upon start, while gyroscope is calibrating, you shall see head tracker version briefly on the screen. The version is then replaced by 3 horisonal bars, one for each axis: roll, pitch and yaw.
+If you have a LED `128x32` screen added you your board (via I2C), the board's bluetooth address is displayed on it. Blinking ":" symbols indicate bluetooth connection status, like blue led. Upon start, while gyroscope is calibrating, you shall see head tracker version briefly on the screen. The version is then replaced by 3 horisonal bars, one for each axis: roll, pitch and yaw.
 
 
 ## Connect to radio

src/main.go

@@ -29,6 +29,7 @@ const flashStoreTreshold = 10_000
 var (
 	d *display.Display
 	t trainer.Trainer
+	i *orientation.IMU
 	o *orientation.Orientation
 	f *Flash
 )
@@ -40,7 +41,8 @@ func init() {
 	initExtras()
 
 	// Orientation
-	o = orientation.New()
+	i = orientation.NewIMU()
+	o = orientation.New(i)
 	o.Configure(PERIOD * time.Millisecond)
 
 	// Trainer (Bluetooth or PPM)
@@ -149,9 +151,11 @@ func main() {
 	iter = 0
 	for {
 
-		if !pinResetCenter.Get() { // Low means button pressed => shall reset center
+		if !pinResetCenter.Get() || (iter%400 == 0 && i.ReadTap()) { // Button pressed OR [double] tap registered (shall not read register more frequently than double tap duration)
 			o.Reset()
-			continue
+			on(ledR)
+		} else {
+			off(ledR)
 		}
 
 		o.Update()

src/orientation/imu_nano-33-ble.go

@@ -63,3 +63,7 @@ func (imu *IMU) Read() (gx, gy, gz, ax, ay, az float64, err error) {
 	ax, ay, az = float64(-axi)/1000000, float64(ayi)/1000000, float64(azi)/1000000
 	return
 }
+
+func (imu *IMU) ReadTap() (tap bool) {
+	return false // TODO implemented tap detection on Nano 33 BLE
+}

src/orientation/imu_xiao-ble.go

@@ -9,6 +9,15 @@ import (
 	"tinygo.org/x/drivers/lsm6ds3tr"
 )
 
+const (
+	TAP_SRC     = 0x1C
+	TAP_CFG     = 0x58
+	TAP_THS_6D  = 0x59
+	INT_DUR2    = 0x5A
+	WAKE_UP_THS = 0x5B
+	MD1_CFG     = 0x5E
+)
+
 type IMU struct {
 	device *lsm6ds3tr.Device
 	gyrCal *GyrCal
@@ -34,12 +43,24 @@ func (imu *IMU) Configure() {
 	// Configure IMU
 	imu.device = lsm6ds3tr.New(machine.I2C1)
 	imu.device.Configure(lsm6ds3tr.Configuration{
-		AccelRange:      lsm6ds3tr.ACCEL_4G,
-		AccelSampleRate: lsm6ds3tr.ACCEL_SR_833,
-		GyroRange:       lsm6ds3tr.GYRO_500DPS,
-		GyroSampleRate:  lsm6ds3tr.GYRO_SR_833,
+		AccelRange:      lsm6ds3tr.ACCEL_4G,     // 4g
+		AccelSampleRate: lsm6ds3tr.ACCEL_SR_833, // every ~1.2ms
+		GyroRange:       lsm6ds3tr.GYRO_500DPS,  // 500 deg/s
+		GyroSampleRate:  lsm6ds3tr.GYRO_SR_833,  // every ~1.2ms
 	})
 
+	tapConfig := map[byte]byte{
+		TAP_CFG:     0x8F, // interrupts enable + tap all axes + latch (saves the state of the interrupt until register is read)
+		TAP_THS_6D:  0x01, // tap threshold
+		INT_DUR2:    0xFF, // tap sensing params: duration = 16*([7:4]+1)*1.2ms, quiet = 2*([3:2]+1)*1.2ms, shock = 4*([1:0]+1)*1.2ms => 0xFF = 307.2ms, 10.8ms, 4.8ms
+		WAKE_UP_THS: 0x80, // enable double tap events
+		MD1_CFG:     0x08, // route double tap events to INT1 (requited for the latch to work)
+	}
+
+	for reg, val := range tapConfig {
+		machine.I2C1.WriteRegister(uint8(imu.device.Address), reg, []byte{val})
+	}
+
 }
 
 func (imu *IMU) Read() (gx, gy, gz, ax, ay, az float64, err error) {
@@ -61,3 +82,9 @@ func (imu *IMU) Read() (gx, gy, gz, ax, ay, az float64, err error) {
 	ax, ay, az = float64(-axi)/1000000, float64(ayi)/1000000, float64(azi)/1000000
 	return
 }
+
+func (imu *IMU) ReadTap() (tap bool) {
+	data := []byte{0x00}
+	machine.I2C1.ReadRegister(uint8(imu.device.Address), TAP_SRC, data)
+	return data[0]&0x10 != 0
+}

src/orientation/orientation.go

@@ -18,9 +18,9 @@ type Orientation struct {
 	current mgl.Quat
 }
 
-func New() *Orientation {
+func New(imu *IMU) *Orientation {
 	return &Orientation{
-		imu:    NewIMU(),
+		imu:    imu,
 		offset: mgl.QuatIdent(),
 	}
 }