Cloud Bluemix Demo

Demonstrates IBM Bluemix communication over the MQTT protocol

SDK directory: apps/cloud/bluemix

API Features Demonstrated

MQTT Protocol Library

Platforms

This app works on:

AMW004-E03 - Zentri Mackerel evaluation board
AMW106-E03 - Zentri Moray evaluation board
NXP-SCCK - NXP Secure Cloud Connectivity Kit - Note that for this device the periodic_publish function must be modified to use a different sensor.
Avnet BCM4343W - Avnet IoT Starter Kit - Note that for this device the periodic_publish function must be modified to use a different sensor.

Requirements and Prerequisites

This app requires ZentriOS 3.1+.

The application is written to transmit thermistor data. The Zentri AMW004-E03 and AWM106-E03 evaluation boards have a thermistor connected to a standard ADC and GPIO.

For other platforms you can substitute another data source, by modifying the periodic_publish function.

Resources

The manifest.json file is configured to download two lookup tables to the device:

resources/lut_10bit.csv
resources/lut_12bit.csv

Description

This demonstration does not require a user account or security certificates.

The application connects to the Bluemix Quickstart broker: quickstart.messaging.internetofthings.ibmcloud.com

After connection is established, the app periodically reads the thermistor and converts the value to temperature, using lookup tables. It also reads the signal strength of the Access Point. The result is then published to the quickstart topic. The period is by default 5 seconds.

You can view a graph of the transmitted values on the IBM Quickstart IoT site:

https://quickstart.internetofthings.ibmcloud.com

Usage Instructions

Open a ZentriOS serial terminal to the device. See Getting Started, Opening a ZentriOS Terminal.

This app assumes your ZentriOS device is set up with the credentials to join your local network. If you have not already set up network credentials, on the ZentriOS terminal, run the commands:

network_up -s
save

See the Wi-Fi Command API documentation for network_up and save.

On starting up, the app displays messages similar to the following on the ZentriOS terminal:

> Network is down, restarting...
[Associating to Zentri_Guest]
> Security type from probe: WPA2-AES
Obtaining IPv4 address via DHCP
IPv4 address: 192.168.6.113
[Associated]
>
IBM Bluemix MQTT Demo Application Started
  - Broker: quickstart.messaging.internetofthings.ibmcloud.com
  - Client ID: d:quickstart:type:zentri_4422
  - Topic/Queue: iot-2/evt/zentri/fmt/json

Opening connection with broker quickstart.messaging.internetofthings.ibmcloud.com:1883
[Opening: quickstart.messaging.internetofthings.ibmcloud.com:1883]
> Resolving host: quickstart.messaging.internetofthings.ibmcloud.com
Connecting (TCP): 184.172.124.189:1883
[2016-03-29 | 06:14:35: Opened: 0]
> Connection established
Connecting...
Send CONNECT frame

If the connection is successful, the app displays messages similar to the following:

Received CONNACK
CONNECTED
Publishing to topic: 'iot-2/evt/zentri/fmt/json', message: '{"d":{"signal strength": -72, "temperature": 25.7693}}'
Send PUBLISH frame
MESSAGE PUBLISHED
Publishing to topic: 'iot-2/evt/zentri/fmt/json', message: '{"d":{"signal strength": -67, "temperature": 25.7436}}'
Send PUBLISH frame
MESSAGE PUBLISHED
Publishing to topic: 'iot-2/evt/zentri/fmt/json', message: '{"d":{"signal strength": -75, "temperature": 25.7693}}'
Send PUBLISH frame
...

To view the transmitted values on the IBM Quickstart IoT site, open the following URL in a browser:

https://quickstart.internetofthings.ibmcloud.com

In the Quickstart page Device ID box, enter the client ID type displayed in the ZentriOS terminal when the app starts up. For example if the app displays:

- Client ID: d:quickstart:type:zentri_4422

then enter zentri_4422 in the Device ID box

The device ID is unique to the device, in the form zentri_xxxx where xxxx represents the least significant 4 bytes of the device WLAN MAC address.

Implementation

common.h

Configuration values and constants

bluemix.c

Sets up global variables:

settings - settings structure
mqtt_connection - object to hold MQTT connection details
callback - mqtt_connection_event_cb connection handler callback

zn_app_init

Starts up the network if required with zn_network_restart
Initalises the thermistor ADC
Initialises the lookup table
Allocates memory for an MQTT connection object with zn_malloc
Initialises the MQTT connection object with mqtt_init
Calls mqtt_app_connect to connect to the IBM cloud service

mqtt_app_connect

calls mqtt_open to open the connection to the IBM Watson IoT platform Quickstart site.
- If unsuccessful, logs an error and returns.
- The connection handler callback function supplied is the static function mqtt_connection_event_cb. This function is called on any subsequent connection event.
On successful open, calls mqtt_connect to send the CONNECT message requesting a connection.
- Note how memory for the conninfo is allocated
- The connection info includes a keepalive period and the client ID.

mqtt_connection_event_cb

Callback to handle connection events
- On successful connection event, issues a one-off event periodic_publish
- On subsequent publish events, issues a timed periodic_publish event

periodic_publish

Sends a message with the ADC temperature value and the RSSI reading. On a platform with other sensors, you can modify this function to send an appropriate value.
- calls zn_issue_command_return_data to issue the wlan_get_rssi command and return the value.
- gets the ADC value with zn_adc_gpio_to_peripheral. Logs error if unsuccessful.
- reads ADC value as temperature using the previously set up lookup table with zn_adc_sample_and_convert. Logs error if unsuccessful.
- converts the floating point temperature to a string and formats as an MQTT message in the global settings.message.
- calls mqtt_app_publish to publish the message

mqtt_app_publish

calls mqtt_publish to publish settings.message to the topic settings.topic using the connection mqtt.connection. Logs an error if unsuccessful.

Source

See: