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platform device language
linux
vho1-x
c

Run a simple C sample on VHo1-X running Linux Beaglebone 3.2.0

Table of Contents

Introduction

About this document

This document describes how to connect VHo1-X device running Linux with Azure IoT SDK. This multi-step process includes:

  • Configuring Azure IoT Hub
  • Registering your IoT device
  • Build and deploy Azure IoT SDK on device

Step 1: Prerequisites

You should have the following items ready before beginning the process:

Step 2: Prepare your Device

  • Connect the VHo1-X using the twisted pair for SDK download and data transfer.

Step 3: Setup the development environment

This section shows you how to set up a development environment for the Azure IoT device SDK for C on VHo1-X.

Install dependencies under /usr/lib

  • Download curl-7.49.1.tar.gz and openssl-1.0.2h.tar.gz for cross compiling.

  • Download the Microsoft Azure IoT Device SDK by issuing following command:

     git clone --recursive https://github.com/Azure/azure-iot-sdks.git

  • Navigate to the folder c/build_all/linux in your local copy of the repository.

Step 4: Build and Run the sample

4.1 Setting up cmake to cross compile

  • Switch to the SDK directory tree.

    cd ~/azure-iot-sdks/c/build_all/linux

  • Using the text editor of your choice, create a new file in this directory and call it toolchain-rpi.cmake and add following lines to it:

    INCLUDE(CMakeForceCompiler)

SET(CMAKE_SYSTEM_NAME Linux)     # this one is important
SET(CMAKE_SYSTEM_VERSION 1)     # this one not so much

# this is the location of the arm toolchain targeting the beaglebone
SET(CMAKE_C_COMPILER ~/cross_tools/linux-devkit/bin/arm-arago-linux-gnueabi-gcc)

# this is the file system root of the target
SET(CMAKE_FIND_ROOT_PATH ~/cross_tools/linux-devkit/)

# search for programs in the build host directories
SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)

# for libraries and headers in the target directories
SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

  • Save the toolchain file. Your cross compilation environment is now complete.

4.2 Build the sample

  • Edit the following file using any text editor of your choice: azure-iot-sdks/c/iothub_client/samples/iothub_client_sample_mqtt/iothub_client_sample_mqtt.c

  • Find the following place holder for IoT connection string:

    static const char* connectionString = "[device connection string]";

  • Replace the above placeholder with device connection string you obtained in Step 1 and save the changes.

  • Add certificates define.

    const char certificates[];

    if (IoTHubClient_LL_SetOption(iotHubClientHandle, "TrustedCerts", certificates) != IOTHUB_CLIENT_OK)
{
    printf("failure to set option \"TrustedCerts\"\r\n");
}

  • Conditional compile on the above code to pass certificate.

  • Because cross compiling toolchain gcc version is 4.5.3, /c/serializer/inc/agenttypesystem.h code must be modified to pass compiling.

    Del Line33:typedef struct AGENT_DATA_TYPE_TAG AGENT_DATA_TYPE;
Del Line540:AGENT_DATA_TYPE* value;
Add Line540:struct AGENT_DATA_TYPE_TAG * value;

  • Build the SDK using following command.

    sudo ./azure-iot-sdks/c/build_all/linux/build.sh --toolchain-file toolchain-rpi.cmake  --no-amqp --no-http --skip-unittests  -cl -DMBED_BUILD_TIMESTAMP | tee LogFile.txt
## 4.3 Deploy the sample
  • Transfer following libraries to target board directory /usr/lib. 
    libcrypto.so.1.0.0
libssl.so.1.0.0
libcurl.so.4.4.0
  • Transfer the sample executable iothub_client_sample_mqtt to target board directory /usr/local/bin.

***Note:***Because sample code is compiled with 'TrustedCerts', there is no need to install certificates.

  • Before run the sample ,the device must clock calibrating ,use following command to calibrate.

    ntpdate [NtpServer]
## 4.4 Send Device Events to IoT Hub: 
    /usr/local/bin/iothub_client_sample_mqtt
  • See Manage IoT Hub to learn how to observe the messages IoT Hub receives from the application.

4.5 Receive messages from IoT Hub

  • See Manage IoT Hub to learn how to send cloud-to-device messages to the application.