Google IoT and MQTT

[panda]

Re: [SiPy](Micropython and Google IoT Core MQTT)

I was able to make this work. What made this doable is using the new pycom ucrypto library. Previously it would take ~5 minutes to generate a JWT signature. The following repository has what should be placed in /flash/lib

https://github.com/innoagg/pycom_google_iot

Next you need to setup your Google IoT registry and download the private key from that process. See these steps:

https://cloud.google.com/iot/docs/how-tos/mqtt-bridge#downloading_mqtt_server_certificates

From the steps above you should have created a private key for the device. Place this key in /flash/cert

Next you must build a configuration file with details from the Google IoT instance. here is an example mqtt_config.py that I used:

google_cloud_config = {
    'project_id':'XXX',
    'cloud_region':'us-central1',
    'registry_id':'XXX',
    'device_id':'XXX',
    'mqtt_bridge_hostname':'mqtt.googleapis.com',
    'mqtt_bridge_port':8883
}

jwt_config = {
    'algorithm':'RS256',
    'token_ttl': 43200, #12 hours
    'private_key':""
}

try:
    log.info("Loading RSA Private Key...")
    with open('/flash/cert/private_key.pem','rb') as f:
        jwt_config['private_key'] = f.read()
        print(jwt_config['private_key'])
    f.close()
    log.info("RSA Private Key Loaded")
except Exception as e:
    log.error("Error Loading RSA Private Key: {}".format(e))
    jwt_config['private_key']

Finally, use a similar procedure to return an MQTT client:

import mqtt_config
import microjwt
from umqtt.simple import MQTTClient
import machine
import time
from network import WLAN
from machine import RTC
import ujson

print("connect wifi")

wlan = WLAN(mode=WLAN.STA)
wlan.connect("XXX", auth=(WLAN.WPA2, "XXX"), timeout=5000)

while not wlan.isconnected():
    machine.idle()

rtc = RTC()
rtc.init()

if not rtc.synced():
    rtc.ntp_sync("pool.ntp.org")
    while not rtc.synced():
        print("RTC Syncing...")
        time.sleep_ms(500)

print("RTC Time:{}".format(time.time()))

print(wlan.ifconfig())

print("wifi connected")

def on_message(topic, msg):
   print("Topic:{}  Msg:{}".format(topic, msg))

def get_mqtt_client(project_id, cloud_region, registry_id, device_id, jwt):
    """Create our MQTT client. The client_id is a unique string that identifies
    this device. For Google Cloud IoT Core, it must be in the format below."""
    client_id = 'projects/{}/locations/{}/registries/{}/devices/{}'.format(project_id, cloud_region, registry_id, device_id)
    print('Sending message with password {}'.format(jwt))
    client = MQTTClient(client_id.encode('utf-8'),server=mqtt_config.google_cloud_config['mqtt_bridge_hostname'],port=mqtt_config.google_cloud_config['mqtt_bridge_port'],user=b'unused',password=jwt.encode('utf-8'),ssl=True)
    client.set_callback(on_message)
    client.connect(clean_session=True)
    client.subscribe('/devices/{}/config'.format(device_id), 1)
    client.subscribe('/devices/{}/commands/#'.format(device_id), 1)
    return client

print("generate jwt")
jwtObj = microjwt.new(mqtt_config.google_cloud_config['project_id'], mqtt_config.jwt_config['private_key'], 'RS256', mqtt_config.jwt_config['token_ttl'])
jwt = jwtObj.encodedValue()

client = get_mqtt_client(mqtt_config.google_cloud_config['project_id'], mqtt_config.google_cloud_config['cloud_region'], mqtt_config.google_cloud_config['registry_id'], mqtt_config.google_cloud_config['device_id'], jwt)

temp = 0;
def pub():
    global temp
    temp = temp + 1
    message = {
        "device_id": mqtt_config.google_cloud_config['device_id'],
        "temp": temp
    }
    print("Publishing message "+str(ujson.dumps(message)))
    mqtt_topic = '/devices/{}/{}'.format(mqtt_config.google_cloud_config['device_id'], 'events')
    client.publish(mqtt_topic.encode('utf-8'), ujson.dumps(message).encode('utf-8'))

def checkMessages():
    print("Check Messages...")
    client.check_msg()
    time.sleep(1)

[BetterAuto]

Hey @panda are you still out there? What firmware version did you test this on? I can't get any other Google IoT libraries to work due to various firmware bugs and want to try your implementation.

[panda]

Also refer to the mqtt library used and included in my repository:

https://github.com/micropython/micropython-lib/tree/master/umqtt.simple