feat(ecg-app): add pause-mode

with longer 1s press on the TOP_RIGHT buttont you can pause the screen
update. You can then scroll through the increases 4s buffer with
BUTTON_LEFT and BOTTOM_RIGHT. Another press on TOP_RIGHT brings you back
into the normal mode.

The logging operation doesn't get interrupted when pausing the screen.

preload/apps/ecg/__init__.py

-import os
-import display
-import utime
-import buttons
-import max30001
-import math
-import struct
-
-WIDTH = 160
-HEIGHT = 80
-OFFSET = 50
-ECG_RATE = 128
-HISTORY_MAX = ECG_RATE * 2
-DRAW_AFTER_SAMPLES = 5
-SCALE_FACTOR = 30
-MODE_USB = "USB"
-MODE_FINGER = "Finger"
-FILEBUFFERBLOCK = 4096
-COLOR_BACKGROUND = [0, 0, 0]
-COLOR_LINE = [255, 255, 255]
-COLOR_TEXT = [255, 255, 255]
-COLOR_MODE_FINGER = [0, 255, 0]
-COLOR_MODE_USB = [0, 0, 255]
-COLOR_WRITE_FG = [255, 255, 255]
-COLOR_WRITE_BG = [255, 0, 0]
-
-current_mode = MODE_FINGER
-history = []
-filebuffer = bytearray()
-write = 0
-bias = True
-update_screen = 0
-pause_screen = 0
-sensor = 0
-disp = display.open()
-
-
-def callback_ecg(datasets):
-    global update_screen, history, filebuffer, write
-    if len(datasets) > 0:
-        for value in datasets:
-            history.append(value)
-        update_screen += len(datasets)
-    if len(history) > HISTORY_MAX:
-        r = len(history) - HISTORY_MAX
-        for i in range(r):
-            history.pop(0)
-
-    # buffer for writes
-    if write > 0:
-        if len(datasets) > 0:
-            for value in datasets:
-                filebuffer.extend(struct.pack("h", value))
-                if len(filebuffer) >= FILEBUFFERBLOCK:
-                    write_filebuffer()
-
-    # don't update on every callback
-    if update_screen >= DRAW_AFTER_SAMPLES:
-        # print("history: %i, filebuffer: %i" % (len(history), len(filebuffer)))
-        draw_histogram()
-        update_screen = 0
-
-
-def write_filebuffer():
-    global write, filebuffer
-    # write to file
-    chars = ""
-    lt = utime.localtime(write)
-    filename = "/ecg-%04d-%02d-%02d_%02d%02d%02d.log" % (
-        lt[0],
-        lt[1],
-        lt[2],
-        lt[3],
-        lt[4],
-        lt[5],
-    )
-
-    # write stuff to disk
-    # print("Write %i bytes to %s" % (len(filebuffer), filename))
-    try:
-        f = open(filename, "ab")
-        f.write(filebuffer)
-        f.close()
-    except OSError as e:
-        print("Please check the file or filesystem", e)
-        write = 0
-        pause_screen = -1
-        disp.clear(COLOR_BACKGROUND)
-        disp.print("IO Error", posy=0, fg=COLOR_TEXT)
-        disp.print("Please check", posy=20, fg=COLOR_TEXT)
-        disp.print("your", posy=40, fg=COLOR_TEXT)
-        disp.print("filesystem", posy=60, fg=COLOR_TEXT)
-        disp.update()
-        close_sensor()
-    except:
-        print("Unexpected error, stop writeing logfile")
-        write = 0
-
-    filebuffer = bytearray()
-    return
-
-
-def open_sensor():
-    global sensor
-    sensor = max30001.MAX30001(
-        usb=(False if current_mode == MODE_FINGER else True),
-        bias=bias,
-        sample_rate=ECG_RATE,
-        callback=callback_ecg,
-    )
-
-
-def close_sensor():
-    global sensor
-    sensor.close()
-
-
-def toggle_mode():
-    global current_mode
-    close_sensor()
-    current_mode = MODE_USB if current_mode == MODE_FINGER else MODE_FINGER
-    open_sensor()
-
-
-def toggle_bias():
-    global bias
-    close_sensor()
-    bias = False if bias == True else True
-    open_sensor()
-    return
-
-
-def toggle_write():
-    global write, disp, pause_screen
-    pause_screen = utime.time_ms() + 1000
-    disp.clear(COLOR_BACKGROUND)
-    if write > 0:
-        write_filebuffer()
-        write = 0
-        disp.print("Stop", posx=50, posy=20, fg=COLOR_TEXT)
-        disp.print("logging", posx=30, posy=40, fg=COLOR_TEXT)
-    else:
-        filebuffer = bytearray()
-        write = utime.time()
-        disp.print("Start", posx=45, posy=20, fg=COLOR_TEXT)
-        disp.print("logging", posx=30, posy=40, fg=COLOR_TEXT)
-
-    disp.update()
-    return
-
-
-def draw_histogram():
-    global disp, history, current_mode, bias, write, pause_screen
-
-    # skip rendering due to message beeing shown
-    if pause_screen == -1:
-        return
-    elif pause_screen > 0:
-        t = utime.time_ms()
-        if t > pause_screen:
-            pause_screen = 0
-        else:
-            return
-
-    disp.clear(COLOR_BACKGROUND)
-
-    # get max value and calc scale
-    value_max = 0
-    for value in history:
-        if abs(value) > value_max:
-            value_max = abs(value)
-    scale = SCALE_FACTOR / (value_max if value_max > 0 else 1)
-
-    # draw histogram
-    old = False
-    x = 0
-    samples = len(history)
-    for i, value in enumerate(history):
-        if old == False:
-            old = (x, int(value * scale) + OFFSET)
-            x += 1
-            continue
-        elif i > samples - WIDTH:
-            disp.line(old[0], old[1], x, int(value * scale) + OFFSET, col=COLOR_LINE)
-            old = (x, int(value * scale) + OFFSET)
-            x += 1
-
-    # draw text: mode/bias/write
-    disp.print(
-        current_mode + ("+Bias" if bias else ""),
-        posx=0,
-        posy=0,
-        fg=(COLOR_MODE_FINGER if current_mode == MODE_FINGER else COLOR_MODE_USB),
-    )
-
-    # announce writing ecg log
-    if write > 0:
-        t = utime.time()
-        if write > 0 and t % 2 == 0:
-            disp.print("LOG", posx=0, posy=60, fg=COLOR_WRITE_FG, bg=COLOR_WRITE_BG)
-
-    disp.update()
-
-
-def main():
-    # show button layout
-    disp.clear(COLOR_BACKGROUND)
-    disp.print("  BUTTONS  ", posx=0, posy=0, fg=COLOR_TEXT)
-    disp.print("Finger/USB>", posx=0, posy=20, fg=COLOR_MODE_FINGER)
-    disp.print("     Bias >", posx=0, posy=40, fg=COLOR_MODE_USB)
-    disp.print("< Write Log", posx=0, posy=60, fg=COLOR_WRITE_BG)
-    disp.update()
-    utime.sleep(3)
-
-    # start ecg
-    open_sensor()
-    while True:
-        button_pressed = False
-        while True:
-            v = buttons.read(
-                buttons.BOTTOM_LEFT | buttons.BOTTOM_RIGHT | buttons.TOP_RIGHT
-            )
-            if v == 0:
-                button_pressed = False
-
-            if not button_pressed and v & buttons.BOTTOM_LEFT != 0:
-                button_pressed = True
-                toggle_write()
-
-            elif not button_pressed and v & buttons.BOTTOM_RIGHT != 0:
-                button_pressed = True
-                toggle_bias()
-
-            elif not button_pressed and v & buttons.TOP_RIGHT != 0:
-                button_pressed = True
-                toggle_mode()
-
-        pass
-
-
-if __name__ == "__main__":
-    main()
+import os
+import display
+import utime
+import buttons
+import max30001
+import math
+import struct
+
+WIDTH = 160
+HEIGHT = 80
+OFFSET_Y = 49
+ECG_RATE = 128
+HISTORY_MAX = ECG_RATE * 4
+DRAW_AFTER_SAMPLES = 5
+SCALE_FACTOR = 30
+MODE_USB = "USB"
+MODE_FINGER = "Finger"
+FILEBUFFERBLOCK = 4096
+COLOR_BACKGROUND = [0, 0, 0]
+COLOR_LINE = [255, 255, 255]
+COLOR_TEXT = [255, 255, 255]
+COLOR_MODE_FINGER = [0, 255, 0]
+COLOR_MODE_USB = [0, 0, 255]
+COLOR_WRITE_FG = [255, 255, 255]
+COLOR_WRITE_BG = [255, 0, 0]
+
+current_mode = MODE_FINGER
+history = []
+filebuffer = bytearray()
+write = 0
+bias = True
+update_screen = 0
+pause_screen = 0
+pause_histogram = False
+histogram_offset = 0
+sensor = 0
+disp = display.open()
+
+
+def callback_ecg(datasets):
+    global update_screen, history, filebuffer, write
+    update_screen += len(datasets)
+
+    # update histogram datalist
+    if pause_histogram == False:
+        if len(datasets) > 0:
+            for value in datasets:
+                history.append(value)
+        if len(history) > HISTORY_MAX:
+            r = len(history) - HISTORY_MAX
+            for i in range(r):
+                history.pop(0)
+
+    # buffer for writes
+    if write > 0:
+        if len(datasets) > 0:
+            for value in datasets:
+                filebuffer.extend(struct.pack("h", value))
+                if len(filebuffer) >= FILEBUFFERBLOCK:
+                    write_filebuffer()
+
+    # don't update on every callback
+    if update_screen >= DRAW_AFTER_SAMPLES:
+        draw_histogram()
+
+
+def write_filebuffer():
+    global write, filebuffer
+    # write to file
+    chars = ""
+    lt = utime.localtime(write)
+    filename = "/ecg-%04d-%02d-%02d_%02d%02d%02d.log" % (
+        lt[0],
+        lt[1],
+        lt[2],
+        lt[3],
+        lt[4],
+        lt[5],
+    )
+
+    # write stuff to disk
+    try:
+        f = open(filename, "ab")
+        f.write(filebuffer)
+        f.close()
+    except OSError as e:
+        print("Please check the file or filesystem", e)
+        write = 0
+        pause_screen = -1
+        disp.clear(COLOR_BACKGROUND)
+        disp.print("IO Error", posy=0, fg=COLOR_TEXT)
+        disp.print("Please check", posy=20, fg=COLOR_TEXT)
+        disp.print("your", posy=40, fg=COLOR_TEXT)
+        disp.print("filesystem", posy=60, fg=COLOR_TEXT)
+        disp.update()
+        close_sensor()
+    except:
+        print("Unexpected error, stop writeing logfile")
+        write = 0
+
+    filebuffer = bytearray()
+    return
+
+
+def open_sensor():
+    global sensor
+    sensor = max30001.MAX30001(
+        usb=(False if current_mode == MODE_FINGER else True),
+        bias=bias,
+        sample_rate=ECG_RATE,
+        callback=callback_ecg,
+    )
+
+
+def close_sensor():
+    global sensor
+    sensor.close()
+
+
+def toggle_mode():
+    global current_mode
+    close_sensor()
+    current_mode = MODE_USB if current_mode == MODE_FINGER else MODE_FINGER
+    open_sensor()
+
+
+def toggle_bias():
+    global bias
+    close_sensor()
+    bias = False if bias == True else True
+    open_sensor()
+    return
+
+
+def toggle_write():
+    global write, disp, pause_screen
+    pause_screen = utime.time_ms() + 1000
+    disp.clear(COLOR_BACKGROUND)
+    if write > 0:
+        write_filebuffer()
+        write = 0
+        disp.print("Stop", posx=50, posy=20, fg=COLOR_TEXT)
+        disp.print("logging", posx=30, posy=40, fg=COLOR_TEXT)
+    else:
+        filebuffer = bytearray()
+        write = utime.time()
+        disp.print("Start", posx=45, posy=20, fg=COLOR_TEXT)
+        disp.print("logging", posx=30, posy=40, fg=COLOR_TEXT)
+
+    disp.update()
+    return
+
+
+def toggle_pause():
+    global pause_histogram, histogram_offset, history
+    if pause_histogram == True:
+        pause_histogram = False
+        history = []
+    else:
+        pause_histogram = True
+    histogram_offset = 0
+
+
+def draw_histogram():
+    global disp, history, current_mode, bias, write, pause_screen, update_screen
+
+    # skip rendering due to message beeing shown
+    if pause_screen == -1:
+        return
+    elif pause_screen > 0:
+        t = utime.time_ms()
+        if t > pause_screen:
+            pause_screen = 0
+        else:
+            return
+
+    disp.clear(COLOR_BACKGROUND)
+
+    # offset in pause_histogram mode
+    samples = len(history)
+    s_start = samples - (histogram_offset + (ECG_RATE * 2))
+    s_end = samples - (histogram_offset + 1)
+    s_draw = s_end - (WIDTH - 1)
+
+    # get max value and calc scale
+    value_max = 0
+    for i, value in enumerate(history):
+        if i >= s_start and i <= s_end and abs(value) > value_max:
+            value_max = abs(value)
+    scale = SCALE_FACTOR / (value_max if value_max > 0 else 1)
+
+    # draw histogram
+    old = False
+    x = 0
+    for i, value in enumerate(history):
+        if old == False:
+            old = value
+            x += 1
+            continue
+        elif i > s_start and i > s_draw and i < s_end:
+
+            oldy = int(old * scale)
+            if oldy < -SCALE_FACTOR:
+                oldy = -SCALE_FACTOR
+            elif oldy > SCALE_FACTOR:
+                oldy = SCALE_FACTOR
+
+            disp.line(
+                x - 1, oldy + OFFSET_Y, x, int(value * scale) + OFFSET_Y, col=COLOR_LINE
+            )
+            old = value
+            x += 1
+
+    # draw text: mode/bias/write
+    if pause_histogram == True:
+        disp.print(
+            "Pause"
+            + (
+                " -%0.1fs" % (histogram_offset / ECG_RATE)
+                if histogram_offset > 0
+                else ""
+            ),
+            posx=0,
+            posy=0,
+            fg=COLOR_TEXT,
+        )
+    else:
+        disp.print(
+            current_mode + ("+Bias" if bias else ""),
+            posx=0,
+            posy=0,
+            fg=(COLOR_MODE_FINGER if current_mode == MODE_FINGER else COLOR_MODE_USB),
+        )
+
+    # announce writing ecg log
+    if write > 0:
+        t = utime.time()
+        if write > 0 and t % 2 == 0:
+            disp.print("LOG", posx=0, posy=60, fg=COLOR_WRITE_FG, bg=COLOR_WRITE_BG)
+
+    disp.update()
+    update_screen = 0
+
+
+def main():
+    global pause_histogram, histogram_offset
+
+    # show button layout
+    disp.clear(COLOR_BACKGROUND)
+    disp.print("  BUTTONS  ", posx=0, posy=0, fg=COLOR_TEXT)
+    disp.print("Finger/USB>", posx=0, posy=20, fg=COLOR_MODE_FINGER)
+    disp.print("     Bias >", posx=0, posy=40, fg=COLOR_MODE_USB)
+    disp.print("< Write Log", posx=0, posy=60, fg=COLOR_WRITE_BG)
+    disp.update()
+    utime.sleep(3)
+
+    # start ecg
+    open_sensor()
+    while True:
+        button_pressed = {"BOTTOM_LEFT": 0, "BOTTOM_RIGHT": 0, "TOP_RIGHT": 0}
+        while True:
+            v = buttons.read(
+                buttons.BOTTOM_LEFT | buttons.BOTTOM_RIGHT | buttons.TOP_RIGHT
+            )
+
+            # BUTTOM LEFT
+
+            if button_pressed["BOTTOM_LEFT"] == 0 and v & buttons.BOTTOM_LEFT != 0:
+                button_pressed["BOTTOM_LEFT"] = utime.time_ms()
+                if pause_histogram == False:
+                    toggle_write()
+                else:
+                    l = len(history)
+                    histogram_offset += ECG_RATE / 2
+                    if l - histogram_offset < WIDTH:
+                        histogram_offset = l - WIDTH
+
+            if button_pressed["BOTTOM_LEFT"] > 0 and v & buttons.BOTTOM_LEFT == 0:
+                duration = utime.time_ms() - button_pressed["BOTTOM_LEFT"]
+                button_pressed["BOTTOM_LEFT"] = 0
+
+            # BUTTOM RIGHT
+
+            if button_pressed["BOTTOM_RIGHT"] == 0 and v & buttons.BOTTOM_RIGHT != 0:
+                button_pressed["BOTTOM_RIGHT"] = utime.time_ms()
+                if pause_histogram == False:
+                    toggle_bias()
+                else:
+                    histogram_offset -= ECG_RATE / 2
+                    histogram_offset -= histogram_offset % (ECG_RATE / 2)
+                    if histogram_offset < 0:
+                        histogram_offset = 0
+
+            if button_pressed["BOTTOM_RIGHT"] > 0 and v & buttons.BOTTOM_RIGHT == 0:
+                duration = utime.time_ms() - button_pressed["BOTTOM_RIGHT"]
+                button_pressed["BOTTOM_RIGHT"] = 0
+
+            # TOP RIGHT
+
+            # down, and still pressed
+            if button_pressed["TOP_RIGHT"] > 0 and v & buttons.TOP_RIGHT != 0:
+                duration = utime.time_ms() - button_pressed["TOP_RIGHT"]
+                if duration > 1000:
+                    button_pressed["TOP_RIGHT"] = -1
+                    toggle_pause()
+
+            # register down event
+            elif button_pressed["TOP_RIGHT"] == 0 and v & buttons.TOP_RIGHT != 0:
+                button_pressed["TOP_RIGHT"] = utime.time_ms()
+
+            # register up event but event already called
+            if button_pressed["TOP_RIGHT"] == -1 and v & buttons.TOP_RIGHT == 0:
+                button_pressed["TOP_RIGHT"] = 0
+
+            # register normal up event
+            elif button_pressed["TOP_RIGHT"] > 0 and v & buttons.TOP_RIGHT == 0:
+                duration = utime.time_ms() - button_pressed["TOP_RIGHT"]
+                button_pressed["TOP_RIGHT"] = 0
+                if pause_histogram == True:
+                    toggle_pause()
+                else:
+                    toggle_mode()
+
+        pass
+
+
+if __name__ == "__main__":
+    main()