IoT_ESP_Azure

C-code based on different projects from around the web, adapted to work with an ESP8266 and ESP32. Straight forward code to send and receive (polling) message from an IoT Hub of Azure (direct or through Central)

Innovet

The code was initialy developed and released as a research project, financed by onderwijs.vlaanderen.be. The previous research project was mainly about interfacing sensors and actuators for the IoT scene, while this year the main task was communicating with the Microsoft Azure platform. The combination of the two projects gives a real life IoT application (e.g. monitoring digital power meter).

The first initial release does work on either the ESP8266 or the ESP32. Various options are available, but some are not fully implemented:

Option	ESP8266	ESP32
Azure HUB	X	X
Azure Central	X	X
WiFi	X	X
Ethernet (Wiz5500)	X	/
SSL store	/	/

The code should work with only a few changes, mainly in the config.h file:

Global configuration

When using WiFi, you should ofcourse provide the SSID to connect to #define WIFI_SSID "YOUR-SSID-HERE". When a password is needed to connect to the SSID, also provide #define WIFI_PSK "YOUR-PSWD-HERE"
When using Ethernet, choose for using Ethernet instead of WiFi by providing #define USE_LAN true. When set to another value then true, WiFi will be used. If this define is not provided, WiFi will be used.
The Ethernet relies on the Wiz5500 chip connected to the SPI bus. There are sufficient examples on how to connect on the internet. An example can be found here. The CS line can be choosen freely, but must be provided by #define ETH_CS x, where x is the pin on the ESP8266 being used. The reset is optional for the ESP8266 but will be included in the ESP32 version.

Azure configuration

There are a few options which can be configured:

#define IOT_CENTRAL false will configure the code to use Azure HUB. Is this setting will be placed on true, then Azure CENTRAL will be used. See Azure credentials (further on) to provide the needed credentials to connect to Azure.
#define SAS_RENEW 15 is the time given in minutes between SAS (Shared Access Signatures) renewals. When your SAS is compromised, the attacker can only use it for the maximum of the given time.
#define IOT_UPDATE 300 is the time given in seconds between transmitting messages. The demo code does transmit a JSON based message with a given interval.
#define POLL_TIME 60 is the time given in seconds to check for new messages. Messages transmitted from the cloud to the device will be queued. The ESP will check if messages are enqueued every given interval.

Azure credentials

Depending on using HUB or CENTRAL, the correct credentials should be given.

For HUB, only one connection string should be provided. This connection string does contain all needed settings (HUB connection point, HUB device name and HUB SAS). Provide this in the following way const char* primaireVerbindingsreeks = "HostName=xyz.azure-devices.net;DeviceId=ESP8266;SharedAccessKey=XcDOTsMyDhfFrkKu/WuajID4nx5gdrhfc1InPrLuER8=";
For CENTRAL, the three different settings should be provided seperately. const char* SCOPE_ID = "0ne00241B52";, const char* DEVICE_ID = "1oikfewjvtb"; and const char* DEVICE_KEY = "omvqlYa9x6+uZBGfNdfhghAjv8kRQMVaBzroOc0NDCes=";. All settings can be found in the Azure Portal.

Future releases

Wired ethernet on the ESP32: The ESP32 has an inbuild MAC which does only need an external PHY. Using a MAC+PHY (as the Wiz5500) gives problems with the default libraries. An altered version of the code is currently being tested and will be merged with the tree if found working.
SSL store: The given code uses https. Every time a message thas to be transmitted or received through Azure, the certificate is checked. This certificate is saved in the header file of the azure code.

static const char rootCACertificateCentral[] PROGMEM = R"EOF(
-----BEGIN CERTIFICATE-----
MIIFWjCCBEKgAwIBAgIQD6dHIsU9iMgPWJ77H51KOjANBgkqhkiG9w0BAQsFADBa
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lk+521W+Ncih3HRbvRBE0LWYT8vWKnfjgZKxwHwJ
-----END CERTIFICATE-----
)EOF";

static const char rootCACertificateHub[] PROGMEM = R"EOF(
-----BEGIN CERTIFICATE-----
MIIFWjCCBEKgAwIBAgIQD6dHIsU9iMgPWJ77H51KOjANBgkqhkiG9w0BAQsFADBa
MQswCQYDVQQGEwJJRTESMBAGA1UEChMJQmFsdGltb3JlMRMwEQYDVQQLEwpDeWJl
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lk+521W+Ncih3HRbvRBE0LWYT8vWKnfjgZKxwHwJ
-----END CERTIFICATE-----
)EOF";