An Implementation of MQTT using CC3200

An Implementation of MQTT using CC3200 Ravi Kishore Kodali Department of Electronics and Communication Engineering National Institute Of Technology, Warangal

Abstract—With the advancements in electronics and communication, the electronic devices are being interconnected to create a controlled environment. The number of devices that are being connected to the Internet is booming day-by-day. However, the existing protocols are verbose and overburden the embedded devices having constrained resources in terms of memory, computational power, battery etc. As a relief, certain light weight protocols such as MQTT, CoAP etc. are being developed especially for the devices that are part of Internet of Things network. In this paper, an implementation of Message Queuing Telemetry Transportation (MQTT) using a CC3200 node has been presented. Wi-Fi is used to establish the wireless Internet access to the node and real time tasking is incorporated by TI-RTOS. Various sleep modes in the CC3200 have been made use of to improve power saving. Keywords:CC3200, MQTT, IoT, RTOS

I. I NTRODUCTION Internet of things (IoT) has gained popularity in the recent times owing to its ease in automation. The scenario of the use of Internet has changed from human centric nature to device centric nature. The protocols existing for the Internet of people are effusive and exchange a lot of data to establish reliable communication. The devices connected to the IoT network are essentially embedded devices that have limited processing capabilities and constrained resources in terms of battery, memory and bandwidth. It follows that the protocols used by Internet of people do not suffice the demands of IoT. Hence newer protocols such as MQTT, CoAP etc. are being developed to ideally suit the requirements of these constrained devices and make them smart. In this paper, an insight on IoT and MQTT is presented before heading towards the implementation aspects. Section I introduces this blooming technology by addressing the scope of IoT. A brief review on MQTT is presented in section II. The related work on deploying these evolving protocols to develop IoT based applications is discussed in section III. In the following section, the implementation details including the hardware setup and software implementation are presented. Results have been presented and discussed in section V. Final section concludes the work. II. I NTERNET OF T HINGS Owing to the improvements in the fields of embedded system design, digital computing and communication technology, electronic devices are being provided with intelligence so that they can operate on their own. These devices can be interconnected in a network and intelligently exchange the information. The self-configuration of these

devices can be achieved by allowing them to interact with the real world besides communicating among themselves. Most of the physical devices are being equipped with sensors, micro-controllers and transceivers to interact with the real world, thereby creating a scope to develop a controlled environment. This idea of interconnection of devices to make them smart is referred to as Internet of Things. Though the term Internet of Things it has been hyped in the recent times as the next big thing, it was coined by Kevin Ashton back in the late 1990s [1]. Inanimate things as well as living organisms are increasingly becoming a part of this IoT network. To integrate the human centric Internet and the Internet of things, Cisco coined the term Internet of Everything [2]. In the near future, the number of devices connected will over weigh the total world population. As per the estimates of Cisco (CIBSG), by 2020 about 50 billion devices are to be connected to the Internet as a part of IoT and on an average, 6.58 devices would be connected per person [3]. Internet of things extends a huge potential across diverse fields [4]. It empowers the device to become alive and express itself. Many industries such as health care, agriculture, transportation, manufacture and supply chain are exploiting this blooming technology to improve efficiency and productivity. Smart homes, smart cities, smart farming, etc. are the outcomes of this revolutionary technology. However, as the electronic devices that are part of IoT network are essentially small embedded devices with constrained resources, the protocols existing for the Internet of people cannot be used. There is a need to develop a new architectural framework and protocols for establishment of reliable and efficient connection in the network. Under such scenario many IoT protocols such as CoAP, MQTT, REST APIs etc have been developed at various layers of protocol stack. III. MQTT Message Queuing Telemetry Transport (MQTT) is an easy to implement light weight transport protocol with a 2 byte fixed header [5]. It is a publish/subscribe based protocol that works on TCP and assures the delivery of messages from node to the server. MQTT is a message oriented information exchange protocol that is ideally suited for the IoT nodes, which have limited capabilities and resources. MQTT was initially developed by IBM [6] in 1999 and recently has been

Fig. 1. MQTT publish/subscribe operations

recognized as standard by Organization for the Advancement of Structured Information Standards (OASIS) [7].

Any MQTT connection typically involves two kinds of agents: MQTT clients and MQTT public broker or MQTT server. Data that is being transported by MQTT is referred to as application message. Any device or program that is connected to the network and exchanges application messages through MQTT is called as an MQTT client. MQTT client can be either a publisher or a subscriber. A publisher publishes application messages and a subscriber requests for these application messages. MQTT server is a device or program that interconnects various MQTT clients. It accepts and transmits the application messages among multiple clients connected to it. The devices such as sensors, mobiles etc. are considered as MQTT clients. When an MQTT client has certain information to be broadcast, it publishes the data to the MQTT broker. MQTT broker is responsible for data collection and its organization. The application messages that are published by MQTT client are forwarded to other MQTT clients that subscribe to it. MQTT is designed to simplify the implementation on client by concentrating all the complexities at the broker. Publisher and subscriber are isolated, meaning they need not have to know the existence or application of the other. Before transmitting the application messages, control packets are exchanged based on the QoS associated with them. An MQTT control packet consists of

a fixed header, a variable header and payload. CONNECT, CONNACK, PUBLISH, PUBACK, PUBREC, PUBREL, SUBSCRIBE, SUBACK, etc. are some of the MQTT control packets [8] exchanged between MQTT clients and MQTT server. In MQTT, routing information is provided in terms of hierarchical tree called Topic. Each topic has a topic name and a topic level associated with it. There may be multiple topic levels separated by / in a topic tree. Wildcard characters such as # and + are used to match multiple levels in a topic. MQTT incorporates security measures such as TLS, VPN etc. at various layers of protocol stack. It is necessary to implement authentication and authorization of resources as well as integrity and privacy of application messages. MQTT supports three levels of Quality of Service (QoS) [9] to the client that can be used based on the application. Each of the inbound and outbound application messages is associated with one of the three QoS levels. QoS 0 is fire and forget approach in which the MQTT client sends data to MQTT broker at most once. It is used in case of reliable connections exist between the clients and broker. The guarantee of delivery of message is taken care of underlying network in QoS 0. The receiver does not acknowledge and the sender does not retransmit the messages. QoS 1 is used, when the MQTT client wants to make sure that the information

is described in this paper. In [11] paper, author proposed an intelligent active system that combines the advantages of TDMA and CSMA for route discovery and data sharing based on MQTT. Each node floods the message to the neighboring nodes in order to obtain the routing table. Time is divided into time slots as in TDMA with a small twist that the slots are classified as priority slots, own slots and other slots. Any node can use the slot when it is free as in CSMA. The simulations show that there is an increase in data delivery rate and a decrease in delay.

Fig. 2. MQTT QoS

is transmitted to the MQTT broker. The sender assigns a packet identifier to the application messages and the receiver responds with an acknowledgment if it accepts the message. The transmitter retransmits the unacknowledged application messages. Duplication of messages might be possible in QoS 1, as the receiver treats the packets with same identifier as a new message after it acknowledges the packet. In QoS 2, multiple signals are exchanged by the MQTT client and broker so that the information is transmitted exactly one time, preventing the loss and duplication at the cost of extra overheads. Hence, there is a trade off between reliability and overhead of the message. There is a two step acknowledgment process to publish the message. The receiver, after receiving the message sends a PUBREC to acknowledge the receipt of the packet. The PUBREL is transmitted by the publisher to indicate the release of published message and the PUBCOMP is transmitted by the receiver to indicate the completion of publication. Each of these control packets are transmitted along with their packet identifiers and the duplicate messages are thus discarded. MQTT features a queuing system. If the client that has subscribed to a topic went off-line, MQTT broker buffers the messages and delivers them to the client, as and when the session is enabled. The client and server store the state of the session. The server queues the messages of an active session till it is received by the client. These features make this light weight protocol ideally suited for IoT nodes, which have limited bandwidth and memory.

This [12] paper briefs MQTT as a message oriented paradigm that ideally suit the IoT scenario. It proposes a framework for smart devices and managers in order to relay the messages from and to MQTT brokers. This framework was verified by prototyping a smart bulb using Raspberry-Pi. In [13] paper, the authors developed http based web server to remotely control a peripheral. Data packets of various nodes are analyzed in multiple operating system environments. Faulty nodes are detected by sniffing the data packets of M2M communication. M2M connection is achieved through WiFi and MiWi protocol on CC3200 and Beagle Bone Black through Zena adapter. V. I MPLEMENTATION D ETAILS Three-tier architecture is used as a basic reference to describe a node in IoT network. It consists of perception layer, transmission layer and application layer. The sensors and actuation controls constitute the perception layer, while the transmission layer deals with connectivity and application layer accounts for data storage and processing. The proposed system consists of a sensing unit and an actuation control based on CC3200. On board sensors, push buttons and LEDs form the perception layer in this prototype. The data is transmitted over Wi-Fi. CC3200 is powered by USB cable connected to host PC. This USB connector also communicates with the terminal in host PC through UART denoting the communication status of the device. The sensor data comprises of the readings of TMP006, an on board temperature sensor. This data is published to IBMs MQTT broker. Push buttons on CC3200 also act as publishers, publishing their state to the broker. Three on- board LEDs (Red, Green and Yellow) are the subscribers that subscribe for the commands. Based on these commands, they turn On and Off. A. CC3200

IV. R ELATED W ORK In [10] paper, the author tried to present a review on the pub/sub based MQTT protocol. They proposed an extension to the existing protocol to operate over the nodes of Wireless Sensor Network. They designed the architecture of MQTT-S encompassing MQTT gateways in addition to clients and brokers. An implementation of MQTT-S on IBM test bench

Taking the advantage of ubiquitous wireless Internet access, CC3200 [14], a wireless MCU from Texas Instruments is used to integrate IoT node and gateway. TIs CC3200 is a low cost and low power wireless MCU that on ARM CORTEX M4 at 80MHz. It integrates two subsystems for handling user applications and networking efficiently. CC3200 is a Wi-Fi based development board that supports 802.11 b/g/n standards.

Fig. 4. Texas Instruments CC3200 development board [15]

Fig. 3. Network Setup

With the on-board web server and WiFi support, CC3200 can support HTTP as well as MQTT. With a 256 KB of RAM and 1MB external flash, it supports debugging as well as programming the firmware after the development of application. The sensing unit comprises of on board temperature sensor and accelerometer. The on-board LEDs are used for actuation control in this prototype.

VI. S OFTWARE I MPLEMENTATION

Fig. 5. Screenshot of Code Composer Studio

Code Composer Studio (CCS) from Texas Instruments is used to develop an application on CC3200 to transform it into an MQTT client. CCSV6 [16] is an Eclipse based one that supports overall application development for almost all the micro-controllers from Texas Instruments. With the help of MQTT library in the software development kit package for CC3200, the node can be programmed as MQTT client. TI-RTOS [17] is made use of in the application to create MQTT task that helps to publish the real-time sensor data from CC3200 to the MQTT broker. The status of CC3200 can be displayed over UART through a terminal emulator called TeraTerm [18]. MessageSpirit [19] is the public MQTT broker from IBM that is used to aggregate data. MQTTLens [20], a Google Chrome based GUI tool is used to connect to the MQTT broker and grasp the data being published and subscribed.

Fig. 6. Status of device as seen from TeraTerm

switched ON and OFF. Multiple LEDs can be controlled by using wild cards (+ or #). cc3200 \act \led \# controls red, green and yellow LEDs ON or OFF at the same time. IX. F UTURE W ORK

Fig. 7. Screenshot of MQTTLens

VII. MQTT

CLIENT AND BROKER

C OMMUNICATION

CC3200 has a unique MAC address and DHCP enabled. When it is connected to an access point after satisfying the authenticating credentials, it is assigned a private IP address. Once CC3200 is connected to the Wireless Access Point, it can transmit and receive data over Wi-Fi. Each of the units in perception layer is assigned with a unique topic. These topics provide routing information to IBMs MQTT broker. The topic used by the client units are: Temperature Sensor: cc3200 \sense \temp Push Buttons:cc3200 \sense \sw Red LED: cc3200 \act \led \L1 Green LED: cc3200 \act \led \L2 Yellow LED: cc3200 \act \led \L3 After CC3200 is connected to the access point, the data from the topics cc3200 \sense \ is published to the IBMs MQTT broker using port 1883. The data gets successfully published if this port is open through the firewall. The LEDs are subscribed to the topic cc3200 \act \led for their controlling commands. VIII. R ESULTS

AND

D ISCUSSION

The MQTT client has been able to connect to MQTT broker successfully. The communication between client and broker can be seen from UART terminal connected to CC3200 which acts as MQTT client. The exchanged MQTT messages can also be grasped through MQTT Lens. Each MQTT packet consisted of 2 byte fixed header and 78 bytes of message, which is much smaller than that of HTTP. Thus, it can be noticed that MQTT is a light weight protocol that works well on low bandwidth. The sensor data is successfully published onto the IBM Message sight. Based on the controlling command messages subscribed to the appropriate topics, LEDs can be

With the development of protocols like MQTT, IoT is experiencing rapid growth these days. For prototyping and estimating the performance of MQTT on a node, this study is restricted to small on-board peripherals. However, various devices such as bulb, fan, TV, ACs, irrigation systems etc. can be suitably connected to the General Purpose Input Output (GPIO) pins of CC3200, through relays and amplifiers. This enables the existing devices to be remotely controlled. Multiple sensors such as reed-switch, humidity sensor, gas sensor, current sensor etc. can be integrated into CC3200 and the environment can be monitored. Some rules of automation can be created to provide the actuators with the intelligence based on sensory data and help them configure themselves accordingly. Moreover, a graphic user interface (GUI) can be built in order to personalize and manage the publications and subscriptions among various topics. The web server thus built can incorporate the graphing feature for analytics. X. C ONCLUSIONS The emerging technology of Internet of Things has a great potential in a wide range of fields and its applications is expanding day by day. The number of devices that are being connected to IoT network is sky-rocketing these days. However, the existing protocols seem to overburden the IoT nodes and hence there is a need to focus on new kinds of protocols. A brief overview and implementation of one such light weight protocol -MQTT is presented in this paper. Considering the ease of wireless Internet access through WiFi, MQTT client application is built on CC3200 using Code composer studio and TI-RTOS. The MQTT data packets have been analyzed. The sensors and actuators are remotely monitored and controlled through existing infrastructure of connectivity. Based on the results, it has been observed that the low size headers and multi levels of QoS makes MQTT ideally suitable for IoT nodes. R EFERENCES [1] Rfidjournal.com. That ’Internet of Things’ Thing - RFID Journal . [Online]. Available: http://www.rfidjournal.com/articles/view?4986 [2] An introduction to the internet of things. [Online]. Available: http://www.cisco.com/c/dam/en us/solutions/trends/iot/ introduction to IoT november.pdf [3] D. Evans, “White paper: The internet of things how the next evolution of the internet is changing everything,” Tech. Rep., April 2014. [Online]. Available: http://www.cisco.com/web/about/ac79/docs/innov/ IoT IBSG 0411FINAL.pdf [4] C. reports, “White paper: Reaping the benefits of the internet of things,” Tech. Rep. [Online]. Available: http://www.cognizant.com/InsightsWhitepapers/ Reaping-the-Benefits-of-the-Internet-of-Things.pdf [5] Mqtt v3.1 protocol specification. [Online]. Available: http://public.dhe. ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html [6] Hivemq. [Online]. Available: http://www.hivemq.com/blog/ mqtt-essentials-part-1-introducing-mqtt

[7] Mqtt version 3.1.1 becomes an oasis standard. [Online]. Available: https://www.oasis-open.org/news/announcements/ mqtt-version-3-1-1-becomes-an-oasis-standard [8] Oasis mqtt version 3.1.1. [Online]. Available: http://docs.oasis-open. org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.pdf [9] (2014, October) Mqtt version 3.1.1 oasis standard. [Online]. Available: http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/mqtt-v3.1.1.html [10] null, “Mqtt-s x2014; a publish/subscribe protocol for wireless sensor networks,” in Communication Systems Software and Middleware and Workshops, 2008. COMSWARE 2008. 3rd International Conference on, Jan 2008, pp. 791–798. [11] ——, “Design and simulation of energy efficiency in node based on mqtt protocol in internet of things,” in Green Computing and Internet of Things (ICGCIoT), 2015 International Conference on, Oct 2015, pp. 1413–1417. [12] ——, “Toward the internet of things application and management: A practical approach,” in World of Wireless, Mobile and Multimedia Networks (WoWMoM), 2014 IEEE 15th International Symposium on a, June 2014, pp. 1–6. [13] ——, “Iot based access and analysis of wireless sensor node protocols with low power host connectivity,” in Smart Technologies and Management for Computing, Communication, Controls, Energy and Materials (ICSTM), 2015 International Conference on, May 2015, pp. 372–375. [14] Cc3200 programmable wi-fi mcu datasheet. [Online]. Available: http://www.ti.com/lit/ds/swas032f/swas032f.pdf [15] Ti releases new simplelink wifi cc3200 launchpad. [Online]. Available: http://43oh.com/2014/06/ ti-releases-new-simplelink-wifi-cc3200-launchpad/ [16] Code composer studio - texas instruments wiki. [Online]. Available: http://processors.wiki.ti.com/index.php/Category:Code Composer Studio v6 [17] Ti-rtos texas instruments wiki. [Online]. Available: http://processors.wiki.ti.com/index.php/TI-RTOS?keyMatch=TI% 20rtos&tisearch=Search-EN [18] Tera term open source project. [Online]. Available: https://ttssh2.osdn. jp/index.html.en [19] messagesight.demos.ibm.com. [Online]. Available: messagesight.demos. ibm.com [20] Mqttlens chrome web store. [Online]. Available: https://chrome.google.com/webstore/detail/mqttlens/ hemojaaeigabkbcookmlgmdigohjobjm?hl=en