Merge pull request #1191 from caternuson/clue_alti

Code for CLUE altimeter

Author: TheKitty

CLUE_Altimeter/clue_altimeter.py

@@ -0,0 +1,188 @@
+import time
+import struct
+import displayio
+import terminalio
+from microcontroller import nvm
+from adafruit_display_text import label
+from adafruit_bitmap_font import bitmap_font
+import adafruit_imageload
+from adafruit_clue import clue
+
+# ==| USER CONFIG |=====================
+USE_METRIC = False
+DISPLAY_UPDATE = 1
+HOLD_TO_SET = 1
+FONT = terminalio.FONT
+BLUE = 0x53E4FF
+ORANGE = 0xFCDF03
+RED = 0xFA0000
+DEBOUNCE = 0.05
+SAMPLES = 10
+DELAY = 0.05
+STD_SLP = 1013.25
+# ==| USER CONFIG |=====================
+
+# configure pressure sensor (see Table 15 in datasheet)
+clue._pressure.mode = 0x03  # normal
+clue._pressure.overscan_pressure = 0x05  # x16
+clue._pressure.overscan_temperature = 0x02  # x2
+clue._pressure.iir_filter = 0x02  # 4
+clue._pressure.standby_period = 0x01  # 62.5 ms
+
+# restore saved sea level pressure from NVM
+clue.sea_level_pressure = struct.unpack("f", nvm[0:4])[0]
+
+# --------------------------------------------------------------------
+# D I S P L A Y    S E T U P
+# --------------------------------------------------------------------
+
+# create main display group
+splash = displayio.Group(max_size=4)
+clue.display.show(splash)
+
+# background
+bg_bmp, bg_pal = adafruit_imageload.load(
+    "/network23.bmp", bitmap=displayio.Bitmap, palette=displayio.Palette
+)
+for i, color in enumerate(bg_pal):
+    if color == 0xFF0000:
+        bg_pal.make_transparent(i)
+        break
+background = displayio.TileGrid(bg_bmp, pixel_shader=bg_pal)
+
+# a group for both altitude readouts
+alti_readouts = displayio.Group(max_size=2, scale=6)
+
+# altitude (corrected)
+alti_disp = label.Label(FONT, text="12345", color=ORANGE)
+alti_disp.anchor_point = (0, 0)
+alti_disp.anchored_position = (7, 2)
+
+# altitude (uncorrected)
+alt2_disp = label.Label(FONT, text="12345", color=ORANGE)
+alt2_disp.anchor_point = (0, 0)
+alt2_disp.anchored_position = (7, 15)
+
+# add both alti's to group
+alti_readouts.append(alti_disp)
+alti_readouts.append(alt2_disp)
+
+# barometric pressure and temperature
+aux_data = label.Label(FONT, text="P: 1234.56  T: 123.4", color=BLUE)
+aux_data.anchor_point = (0, 0)
+aux_data.anchored_position = (16, 212)
+
+# calibration mode indicator
+cal_mode = label.Label(FONT, text="   ", color=RED, scale=4, x=150, y=200)
+
+# add everything to splash
+splash.append(background)
+splash.append(alti_readouts)
+splash.append(aux_data)
+splash.append(cal_mode)
+
+# --------------------------------------------------------------------
+# H E L P E R    F U N C T I O N S
+# --------------------------------------------------------------------
+def compute_altitude(barometric_pressure, sea_level_pressure):
+    """Compute altitude (m) from barometric pressure (hPa) and sea level pressure (hPa)."""
+    # https://www.weather.gov/media/epz/wxcalc/pressureAltitude.pdf
+    return 44307.69396 * (1 - pow((barometric_pressure / sea_level_pressure), 0.190284))
+
+
+def compute_sea_level_pressure(barometric_pressure, altitude):
+    """Compute sea level pressure (hPa) from barometric pressure (hPa) and altitude (m)."""
+    return barometric_pressure * pow((1 - (altitude / 44307.69396)), -5.2553)
+
+
+def average_readings(samples=10, delay=0.05):
+    """Return averaged readings for pressure and temperature."""
+    pressure = 0
+    temperature = 0
+    for _ in range(samples):
+        pressure += clue.pressure
+        temperature += clue.temperature
+        time.sleep(delay)
+    return pressure / samples, temperature / samples
+
+
+def recalibrate(current_sea_level_pressure=None):
+    """Enter current altitude."""
+    cal_mode.text = "CAL"
+    alt2_disp.text = "-----"
+    # wait for release if still being held
+    while clue.button_a and clue.button_b:
+        pass
+    # get current value
+    altitude = int(alti_disp.text)
+    done = False
+    while not done:
+        now = time.monotonic()
+        # increase
+        if clue.button_a and not clue.button_b:
+            altitude -= 1
+            time.sleep(DEBOUNCE)
+        # decrease
+        elif clue.button_b and not clue.button_a:
+            altitude += 1
+            time.sleep(DEBOUNCE)
+        # hold both to set
+        elif clue.button_a and clue.button_b:
+            while clue.button_a and clue.button_b:
+                if time.monotonic() - now > HOLD_TO_SET:
+                    print("done")
+                    done = True
+                    break
+        alti_disp.text = "{:5d}".format(altitude)
+    cal_mode.text = "   "
+    # change clue settings
+    if not USE_METRIC:
+        altitude *= 0.3048
+    # get current local pressure
+    barometric_pressure, _ = average_readings(SAMPLES, DELAY)
+    # compute sea level pressure and set
+    clue.sea_level_pressure = compute_sea_level_pressure(barometric_pressure, altitude)
+    # store in NVM for later use
+    nvm[0:4] = struct.pack("f", clue.sea_level_pressure)
+
+
+def update_display():
+    """Update the display with latest info."""
+    barometric_pressure, temperature = average_readings(SAMPLES, DELAY)
+    altitude = compute_altitude(barometric_pressure, clue.sea_level_pressure)
+    alt2tude = compute_altitude(barometric_pressure, STD_SLP)
+    if not USE_METRIC:
+        altitude *= 3.28084  # ft
+        alt2tude *= 3.28084
+        # barometric_pressure *= 0.0145038      # psi
+        temperature = 32 + 1.8 * temperature  # deg F
+    alti_disp.text = "{:5d}".format(int(altitude))
+    alt2_disp.text = "{:5d}".format(int(alt2tude))
+    aux_data.text = "P: {:7.2f}  T: {:5.1f}".format(barometric_pressure, temperature)
+
+
+# --------------------------------------------------------------------
+# M A I N    L O O P
+# --------------------------------------------------------------------
+last_update = time.monotonic()
+
+while True:
+
+    now = time.monotonic()
+
+    # update display with latest info
+    if now - last_update > DISPLAY_UPDATE:
+        update_display()
+        last_update = now
+
+    # hold both to recalibrate
+    if clue.button_a and clue.button_b:
+        # accumulate hold time
+        while clue.button_a and clue.button_b:
+            if time.monotonic() - now > HOLD_TO_SET:
+                print("set")
+                recalibrate(clue.sea_level_pressure)
+                break
+        # wait for release if still being held
+        while clue.button_a and clue.button_b:
+            pass