feat(examples): add example with i2c sensor (si7021 temperature/humid…

…ity)

examples/feather-m4-i2c.py

@@ -0,0 +1,107 @@
+# custom
+from prometheus_express.metric import Counter, Gauge
+from prometheus_express.registry import CollectorRegistry
+from prometheus_express.router import Router
+from prometheus_express.server import start_http_server, await_http_request
+
+# system
+import board
+import busio
+import digitalio
+import random
+import socket
+import time
+
+# hardware
+import adafruit_si7021
+import neopixel
+import wiznet
+
+# colors
+RED = (255, 0, 0)
+GREEN = (0, 255, 0)
+BLUE = (0, 0, 255)
+
+# set up sensor
+i2c = busio.I2C(board.SCL, board.SDA)
+sensor = adafruit_si7021.SI7021(i2c)
+
+# set up networking
+spi = busio.SPI(clock=board.SCK, MOSI=board.MOSI, MISO=board.MISO)
+
+eth = wiznet.WIZNET5K(spi, board.D10, board.D11)
+eth.dhcp = True
+
+# initialize the LEDs
+led = digitalio.DigitalInOut(board.D13)
+led.direction = digitalio.Direction.OUTPUT
+
+rgb = neopixel.NeoPixel(board.NEOPIXEL, 1, brightness=0.2)
+
+
+def check_network():
+    online = eth.connected
+    network = eth.ifconfig()
+
+    led.value = online
+
+    print('Online: {}'.format(online))
+    if online == False:
+        return False
+
+    print('Network: {}'.format(network))
+    if network[0] == '0.0.0.0':
+        return False
+
+    return True
+
+
+def bind():
+    ip_addr = eth.ifconfig()[0]
+    ip_port = 8080
+
+    print('Binding: {}:{}'.format(ip_addr, ip_port))
+    return (start_http_server(ip_port, address=ip_addr), True)
+
+
+def main():
+    ready = False
+    bound = False
+
+    registry = CollectorRegistry(namespace='prom_express')
+    metric_t = Gauge('si7021_temperature',
+                     'temperature from the si7021 sensor', registry=registry)
+    metric_h = Gauge('si7021_humidity',
+                     'humidity from the si7021 sensor', registry=registry)
+
+    def prom_handler(headers, body):
+        return {
+            'status': '200 OK',
+            'content': '\r\n'.join(registry.print()),
+        }
+
+    router = Router([
+        ('GET', '/metrics', prom_handler),
+    ])
+    server = False
+
+    rgb[0] = RED  # starting
+    while ready == False:
+        ready = check_network()
+
+    rgb[0] = BLUE  # connected
+    while bound == False:
+        server, bound = bind()
+
+    rgb[0] = GREEN  # ready
+    while True:
+        metric_h.set(sensor.relative_humidity)
+        metric_t.set(sensor.temperature)
+        try:
+            await_http_request(server, router)
+        except OSError as err:
+            print('Error accepting request: {}'.format(err))
+            server, bound = bind()
+
+
+main()