HW Recap

As previously mentioned, the program runs on:

• Avnet LTE IoT Starter KitAvnet LTE IoT Starter Kit
• LTE IoT Breakout CarrierLTE IoT Breakout Carrier

This LTE IoT Starter Kit comes in two varieties, a North American (NA) Version (M18FG-1) and a Global Version (M18QWG).  The difference between the two are that the NA version uses the North American Cellular Bands and is SIM locked to AT&T while the M18QWG uses the International Cellular Bands and is not SIM locked.  Additionally, the NA SOM is PTCRB but the Global SOM is not. Both SOMs contain Host Mode Firmware which was used for  the PTCRB certification.  Details of the SOM Hardware can be found in the User Manual and the Breakout Carrier schematic (located here). The Breakout Carrier facilitates the Barometer Click  and the Temp&Humidity Click modules that I use in the application. If you don't have these modules or the Breakout Carrier, it is not a problem, as this configuration is checked during startup and if not present, it simply means the Barometer and Humidity measurements will not be sent to Azure.  Assembling the kit simply requires you to connect the Antennas, insert the SIM card, and connect power, then connect the board to your development machine for interaction/programming (see the User Manual if you need details).

Required Software Tools

The development tools are all targeted to a Linux environment but it is possible to run in a virtual machine if necessary.  This is because the eLinux distribution contained in the SOM (and tools utilized) are based on Yocto Linux. To obtain the software, compile the program, and interact with the hardware you will need the following tools:

GIT Distributed Version Control System

This is available at: https://gist.github.com/derhuerst/1b15ff4652a867391f03

The WNC SDK                                                                                                                           

This can be obtained by issuing the command:

git clone http://github.com/Avnet/AvnetWNCSDK

Once cloned, proceed to the AvnetWNCSDK directory and install the tools by executing the command:

sudo ./oecorex-86_64-cortexa7-neon-vfpv4-toolchain-nodistro.0.sh'

After the toolchain has been installed, you will need to add the environment variables (you will need to do this each time you open a new terminal window for development) by executing:

. /usr/local/oecore-x86_64/environment-setup-cortexa7-neon-vfpv4-oe-linux-gnueabi (there is a spaces after the '.')

Install ADB

1. Open up a terminal windows.
2. Install ADB by issuing the command 'sudo apt-get install adb'
3. Copy the file file adbpub.key from the AvnetWNCSDK directory to the ADB directory (cp ./AvnetWNCSDK/adbpub.key ~/.android/). This installs the security key so ADB can access the SK2.
4. Connect your M18Qx to the development PC
5. Verify the ADB connection by listing the attached devices, sudo adb devices When you do this the SK2 should be reported as:

$sudo adb devices 
List of devices attached 
WNC_ADB     device

Once all the tools are installed on your development machine, you are ready to download the example program, build it, then load/execute it.

Get Program Source Code

The source code is available from https://github.com/Avnet/M18QxAzureIoT.  You get this code by issuing the command:

git clone --recurse-submodules https://github.com/Avnet/M18QxAzureIoT

Once cloned, the development directory will resemble:

Azure SDK

The directory msft_azure_iot_sdk (that you obtained when you cloned the application code) contains elements of the Microsoft Azure IoT SDK. I broke it out into its own sub directory because only a sub-set of the SDK is needed for this application.  Microsoft organized the SDK was to support all aspects that the SDK including test-harnesses, multiple development environments, jenkins tools, optional helper tools, etc.  I wanted the SDK to only contain what was needed for this program--the necessary transports, and IoT client software.

The platform directory within msft_azure_iot_sdk is the only directory that contains software that would be modified for this application.  By isolating all changes to the platform directory, the transports, client, and c-utility directories can be easily updated when Microsoft releases new versions. 

MbedTLS

When Building the SDK, there are several options you can use for the SSL layer.  Microsoft has used OpenSSL and WolfSSL in their samples, but I wanted to use ARM's MbedTLS so that is the library I imported.  This library is pulled in when you clone the directory by virtue of the '--recurse-submodules' flag when cloning the M18QxAzureIoT repository.  There are no modifications made to the MbedTLS library itself, it is only compiled and used.

Architecture Overview

Files and Descriptions

These are the repositories that are used in the program.  The msft_azure_iot_sdk is simply a subset of the Microsoft Azure IoT C SDK.

The program uses GNU auto tools as its build system (the Microsoft SDK is setup to use CMAKE).  With GNU auto tools, the "meat" of the build is contained in the Makefile.am file and the configure.ac. The Makefile is created from these two inputs.

These two script files are an aid for remembering the format of the Azure CLI calls for monitoring and sending message.

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