First tests with micropython and MQTT.<\/p>\n
On Ubuntu 17.04:<\/p>\n
If we want to use our system as a MQTT broker, we need the mosquitto daemon. The mosquitto-clients package include commands to test publishing and subscribing from the command line:<\/p>\n
sudo apt-get install mosquitto mosquitto-clients<\/pre>\nTo install micropython just follow instructions for Debian-based systems<\/a>.<\/p>\n
Then we need to install a MQTT library for micropython. Used ‘umqtt.simple<\/a>‘:<\/p>\n
.\/micropython -m upip install micropython-umqtt.simple<\/pre>\nThey have some examples, let’s test ‘example_pub.py<\/a>‘:<\/p>\n
from umqtt.simple import MQTTClient\r\n\r\ndef main(server=\"localhost\"):\r\n c = MQTTClient(\"umqtt_client\", server)\r\n c.connect()\r\n c.publish(b\"foo_topic\", b\"hello\")\r\n c.disconnect()\r\n\r\nif __name__ == \"__main__\":\r\n main()<\/pre>\nThis example publish “hello” message to topic “foo_topic” on a broker on our localhost. If we have installed ‘mosquitto’, it is already started (at least on Ubuntu) so we just need to subscribe for messages under “foo_topic”:<\/p>\n
mosquitto_sub -h localhost -t foo_topic<\/pre>\nWe can now run the example (on another terminal):<\/p>\n
.\/micropython example_pub.py<\/pre>\nand we should get:<\/p>\n
hello<\/pre>\n<\/p>\n
Now let’s use a public MQTT broker. There are several available<\/a> but since we are already using mosquitto client we will also use mosquitto own public broker (i.e. ‘test.mosquitto.org<\/a>‘).<\/p>\n
Since it is a public broker, it has considerable traffic so we use a less general topic:<\/p>\n
from umqtt.simple import MQTTClient\r\n\r\nSERVER='test.mosquitto.org'\r\n\r\ndef main(server=SERVER):\r\n c = MQTTClient(\"umqtt_client\", server)\r\n c.connect()\r\n print(\"Connected\")\r\n c.publish(b\"ev3dev_topic\", b\"Make my day!\")\r\n c.disconnect()\r\n print(\"Sent\")\r\n\r\nif __name__ == \"__main__\":\r\n main()<\/pre>\nAnd we subscribe to it:<\/p>\n
mosquitto_sub -h test.mosquitto.org -t ev3dev_topic<\/pre>\nand it still works. It’s not instant messaging but it sure takes less than a second (please note that a public broker cannot assure 100% availability or performance; even it the service is available performance can be degraded if lots of publishers and subscribers are connected passing lots of messages).<\/p>\n
Now let’s do the opposite – subscribe with micropython. We use another example, ‘example_sub.py’:<\/p>\n
<\/p>\n
import time\r\nfrom umqtt.simple import MQTTClient\r\n\r\n# Publish test messages e.g. with:\r\n# mosquitto_pub -t foo_topic -m hello\r\n\r\nSERVER = \"test.mosquitto.org\"\r\n\r\n# Received messages from subscriptions will be delivered to this callback\r\ndef sub_cb(topic, msg):\r\n print((topic, msg))\r\n\r\ndef main(server=SERVER\"):\r\n c = MQTTClient(\"umqtt_client\", server)\r\n c.set_callback(sub_cb)\r\n c.connect()\r\n c.subscribe(b\"ev3dev_topic\")\r\n while True:\r\n if True:\r\n # Blocking wait for message\r\n c.wait_msg()\r\n else:\r\n # Non-blocking wait for message\r\n c.check_msg()\r\n\r\n # Then need to sleep to avoid 100% CPU usage (in a real\r\n # app other useful actions would be performed instead)\r\n time.sleep(1)\r\n\r\n c.disconnect()\r\n\r\nif __name__ == \"__main__\":\r\n main()<\/pre>\n<\/p>\n
For this script to run we also need ‘time’ library for micropython:<\/p>\n
.\/micropython -m upip install micropython-time<\/pre>\nSo if we now publish something:<\/p>\n
mosquitto_pub -h test.mosquitto.org -t ev3dev_topic -m Yahoo!<\/pre>\nwe’ll get:<\/p>\n
$ .\/micropython testsub.py \r\n(b'ev3dev_topic', b'Yahoo!')<\/pre>\nNext: port this to ev3dev.<\/p>\n
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Now the first test:<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
First tests with micropython and MQTT. On Ubuntu 17.04: If we want to use our system as a MQTT broker, we need the mosquitto daemon. The mosquitto-clients package include commands to test publishing and subscribing from the command line: sudo apt-get install mosquitto mosquitto-clients To install micropython just follow instructions for Debian-based systems. Then we … Continuar a ler “micropython and MQTT”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","enabled":false},"version":2}},"categories":[1],"tags":[],"series":[],"class_list":["post-1184","post","type-post","status-publish","format-standard","hentry","category-sem-categoria"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2Mhyv-j6","_links":{"self":[{"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/posts\/1184","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/comments?post=1184"}],"version-history":[{"count":0,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/posts\/1184\/revisions"}],"wp:attachment":[{"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/media?parent=1184"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/categories?post=1184"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/tags?post=1184"},{"taxonomy":"series","embeddable":true,"href":"https:\/\/ofalcao.pt\/blog\/wp-json\/wp\/v2\/series?post=1184"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}