The TMP36 is a low cost, easy to use sensor that fits well with any project. With the TMP36, adding temperature sensing to your Pycom project is easy! In this tutorial, we will use the Pycom Lopy4, and send our measured data to The Things Network via the LoRa Network!
Here is a schematic for wiring up the TMP36. Keep in mind that the flat face of the sensor is facing TOWARD you in this schematic. In this example, we will be using the Pycom Expansion Board 3.0 and the Pycom Lopy4, but any Pycom board will work! If you are connecting to your Pycom board directly refer to the relevant pinout diagram.
In this example, we have provided the bare minimum needed to interface with a TMP36. Get out there an integrate one into your project!
# Measuring temperature by TMP36 import time import machine adc = machine.ADC() # create an ADC object apin = adc.channel(pin='P16') # create an analog pin on P16 & connect TMP36 while True: print("") print("Reading TMP36 Sensor...") value = apin() print("ADC count = %d" %(value)) # LoPy has 1.1 V input range for ADC temp = ((value * 1100 ) / 4096 - 500) / 10 print("Temperature = %5.1f C" % (temp)) time.sleep(10)
Sending Your Readings to The Things Network
Now that you have a stable reading from the TMP36, we can package our data into bytes and send it to The Things Network. If you want to learn more about connecting your Lopy4 to The Things Network, then check out our TTN Tutorials and our Getting Started with The Things Network Tutorial. Remember to add in your own App EUI and App Key!
# Measuring temperature by TMP36 from network import LoRa import socket import utime import binascii import pycom import ustruct import machine from machine import Pin adc = machine.ADC() # create an ADC object apin = adc.channel(pin=Pin.exp_board.G3) # Lopy4 specific: (pin = 'P16') create an analog pin on P16 & connect TMP36 # Temp measurment def temp_measure(): print("") print("Reading TMP36 Sensor...") value = apin() print("ADC count = %d" %(value)) # LoPy has 1.1 V input range for ADC temp = ((value * 1100 ) / 4096 - 500) / 10 print("Temperature = %5.1f C" % (temp)) return temp # disable LED heartbeat (so we can control the LED) pycom.heartbeat(False) # set LED to red pycom.rgbled(0x7f0000) # lora config lora = LoRa(mode=LoRa.LORAWAN, region=LoRa.AS923) # access info app_eui = binascii.unhexlify('XXXXXXXXXXXXXXX') app_key = binascii.unhexlify('XXXXXXXXXXXXXXXXXXXXXXXXXXXX') # attempt join - continues attempts background lora.join(activation=LoRa.OTAA, auth=(app_eui, app_key), timeout=0) # wait for a connection print('Waiting for LoRaWAN network connection...') while not lora.has_joined(): utime.sleep(1) # if no connection in a few seconds, then reboot if utime.time() > 15: print("possible timeout") machine.reset() pass # we're online, set LED to green and notify via print pycom.rgbled(0x004600) print('Network joined!') # setup the socket s = socket.socket(socket.AF_LORA, socket.SOCK_RAW) s.setsockopt(socket.SOL_LORA, socket.SO_DR, 5) s.setblocking(False) s.bind(1) count = 0 # limit to 200 packets; just in case power is left on while count < 200: # take temp measurment, turn the temp blue when measuring pycom.rgbled(0x00007d) utime.sleep(1) temp = temp_measure() pycom.rgbled(0x004600) # encode the packet, so that it's in BYTES (TTN friendly) # could be extended like this struct.pack('f', temp) + struct.pack('c',"example text") # 'h' packs it into a short, 'f' packs it into a float, must be decoded in TTN packet = ustruct.pack('f', temp) # send the prepared packet via LoRa s.send(packet) # example of unpacking a payload - unpack returns a sequence of #immutable objects (a list) and in this case the first object is the only object print ("Unpacked value is:", ustruct.unpack('f',packet)) # check for a downlink payload, up to 64 bytes rx_pkt = s.recv(64) # check if a downlink was received if len(rx_pkt) > 0: print("Downlink data on port 200:", rx_pkt) pycom.rgbled(0xffa500) input("Downlink recieved, press Enter to continue") pycom.rgbled(0x004600) count += 1 utime.sleep(10)
Decoding on TTN
If you want to learn more about Pycom check out our Pycom Tutorials. If you want to learn more about connecting to The Things Network and using LoRaWAN check out our The Things Network Tutorials. There are many more sensors and devices that can be used with the Pycom Lopy4, get out there and experiment!