Add magnetometer driver & example app

modules/accel_app/__init__.py

@@ -2,7 +2,7 @@
 import tidal
 import accelerometer
 
-class Accel(TextApp):
+class Accel(app.TextApp):
     TITLE = "Accelerometer"
     timer = None
 

modules/app_launcher/__init__.py

@@ -67,6 +67,7 @@ def list_core_apps(self):
             ("Sponsors", "sponsors", "Sponsors"),
             ("Battery", "battery", "Battery"),
             ("Accelerometer", "accel_app", "Accel"),
+            ("Magnetometer", "magnet_app", "Magnetometer"),
             ("Settings", "settings_app", "SettingsApp"),
             # ("Swatch", "swatch", "Swatch"),
             # ("uGUI Demo", "ugui_demo", "uGUIDemo")

modules/magnet_app/__init__.py

@@ -0,0 +1,29 @@
+from app import TextApp
+import magnetometer
+
+class Magnetometer(TextApp):
+    TITLE = "Magnetometer"
+    timer = None
+
+    def on_start(self):
+        super().on_start()
+
+    def on_activate(self):
+        super().on_activate()
+        self.update_screen()
+        self.timer = self.periodic(500, self.update_screen)
+
+    def on_deactivate(self):
+        self.timer.cancel()
+        super().on_deactivate()
+
+    def update_screen(self):
+        win = self.window
+        win.set_next_line(0)
+        win.println()
+
+        (x, y, z) = magnetometer.get_xyz()
+
+        win.println(f"X: {x:0.3g}")
+        win.println(f"Y: {y:0.3g}")
+        win.println(f"Z: {z:0.3g}")

modules/magnetometer.py

@@ -0,0 +1,73 @@
+from tidal import i2c
+import ustruct
+import time
+
+_inited = False
+
+# See https://github.com/emfcamp/TiDAL-Hardware/blob/main/datasheets/QMC7983%20Datasheet%20-NCP-Rev1.0.pdf
+
+DEVICE_ADDR = 0x2C
+
+
+REG_XYZ = 0x0
+REG_STATUS = 0x6
+REG_TOUT_0 = 0x7
+REG_TOUT_1 = 0x8
+REG_CFG = 0x9
+REG_RST = 0xA
+REG_FBR = 0xB
+REG_OTP_RDY = 0xC
+REG_CHIPID = 0xD
+
+_scale = 8
+
+def write(reg, val):
+    i2c.writeto_mem(DEVICE_ADDR, reg, bytes((val,)))
+
+def read(reg, count):
+    return i2c.readfrom_mem(DEVICE_ADDR, reg, count)
+
+def read_val(bytes):
+    return (ustruct.unpack("<h", bytes)[0] / 32768) * _scale
+
+def init():
+    global _inited
+    write(REG_RST, 0x80)
+    time.sleep(0.1)
+
+    write(REG_FBR, 0x0F)
+
+    if (_scale == 16):
+        write(REG_CFG, 0x3D)
+    if (_scale == 12):
+        write(REG_CFG, 0x2D)
+    if (_scale == 8):
+        write(REG_CFG, 0x1D)
+    if (_scale == 2):
+        write(REG_CFG, 0x0D)
+
+    _inited = True
+
+def sleep():
+    global _inited
+    if _inited:
+        print("Magnetometer sleep")
+        write(REG_CFG, 0x00)
+        _inited = False
+
+def check_ready():
+    ready = read(REG_STATUS, 1)[0] & 1
+    if not _inited or not ready:
+        init()
+
+def get_xyz():
+    try:
+        check_ready()
+        rawdata = read(REG_XYZ, 6)
+    except OSError:
+        return (0, 0, 0) # is there something more sensible?
+
+    x = read_val(rawdata[0:2])
+    y = read_val(rawdata[2:4])
+    z = read_val(rawdata[4:6])
+    return (x, y, z)

modules/scheduler.py

@@ -92,6 +92,7 @@ def main(self, initial_app):
 
     def enter(self):
         import accelerometer
+        import magnetometer
         first_time = True
         self._level += 1
         enter_level = self._level
@@ -152,6 +153,7 @@ def enter(self):
 
                     # Other power management actions we want to do before display off
                     accelerometer.sleep()
+                    magnetometer.sleep()
 
                 # Make sure any debug prints show up on the UART
                 tidal_helpers.uart_tx_flush(0)