Presented by: Tanmoy Sen, Amazon Web Services Presented at All Things Open 2020 Abstract: Connecting microcontroller-based devices to the cloud enables data collection, analysis and remote updates to deployed devices. Often, these devices need to cost-effectively connect to a mobile device for provisioning, reading, and security. This talk describes how to easily program, deploy, secure, connect, and manage small, low-power edge devices with the open source real-time OS, FreeRTOS, using different connectivity protocols. You learn how to authenticate microcontroller devices with iOS and Android devices and to monitor, manage, and update firmware using the over-the-air update functionality.

1. © 2020, Amazon Web Services, Inc. or its Affiliates.© 2020, Amazon Web Services, Inc. or its Affiliates.
Tanmoy Sen
Connecting Microcontrollers to the Cloud
Using MQTT, HTTP, and Bluetooth LE
Oct-20, 2020

2. © 2020, Amazon Web Services, Inc. or its Affiliates.
Agenda
• How microcontrollers (MCUs) benefit from the cloud
• Connecting MCUs using MQTT
• Connecting MCUs using HTTP
• Connecting MCUs using Bluetooth LE
• Over-the-air updates

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What is a microcontroller (MCU)?
• Small processor
• Simple, functional tasks
• Resource constrained
• MHz compute speed
• KB of RAM
• Low power

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Data sources

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How MCUs benefit from the cloud
Endpoints
Things
Sense & act
Cloud
Storage & compute
Intelligence
Insights & logic → action
Gateway
Gateway
Fleet
onboarding,
management,
and SW updates
Fleet
audit and
protection
Connecting
devices to
services
IoT data
analytics, actions,
and intelligence
Secure device
connectivity
and messaging

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MCU code space
Communications stack
Security stack
Key management
OTA
Bootloader
Functionality

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FreeRTOS libraries
Local
Connectivity
Cloud
Connectivity
Security OTA &
Code Signing
Communicate with a
gateway device without
a cloud connection
Bluetooth LE
Easily collect data & take
actions on microcontroller
-based devices
MQTT, HTTP
Secure device data
and connections
Deploy security updates,
bug fixes, and firmware
updates to devices in the
field
Real-time OS

8. © 2020, Amazon Web Services, Inc. or its Affiliates.
FreeRTOS libraries
Local
Connectivity
Cloud
Connectivity
Security OTA &
Code Signing
MIT license CustomizableOpen source

9. © 2020, Amazon Web Services, Inc. or its Affiliates.© 2020, Amazon Web Services, Inc. or its Affiliates.
MQTT

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Connecting MCUs to the cloud using MQTT
• Lightweight publish/subscribe
application-layer messaging protocol
• MQTT topic acts as matching
mechanism between publishers and
subscribers
• Three communication patterns: point-
to-point, broadcast, and fan-in
• TLS 1.2, X.509 client certificate Source: AWSWhitepaper - Designing MQTTTopics for AWS IoT Core

11. © 2020, Amazon Web Services, Inc. or its Affiliates.© 2020, Amazon Web Services, Inc. or its Affiliates.
HTTP

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Connecting MCUs to the Cloud using HTTP
Amazon Simple
Storage Service
(Amazon S3)
IoT Devices
HTTPGET/PUT
Why use HTTP for IoT devices?
• For high-bandwidth downloads/uploads
• To conform to existing HTTP-based
legacy systems
HTTP client library supports:
• HTTPS 1.1 with GET/PUT
• Async/sync programming models
• Files storage in any hosted service
• File transfer using TLS1.2

13. © 2020, Amazon Web Services, Inc. or its Affiliates.© 2020, Amazon Web Services, Inc. or its Affiliates.
Bluetooth LE

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Connecting MCUs to the Cloud using Bluetooth LE
Amazon
Cognito
AWS IoT
Bluetooth Low
Energy
Devices

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BLE support in FreeRTOS
• Standardized BLE API
• GAP and GATT profiles in BLE
• Companion iOS and Android SDKs
• Custom profile for MQTT over BLE
• Custom profile for Wi-Fi provisioning over BLE

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Custom profile: MQTT over BLE
• Connect BLE devices to AWS
IoT via mobile devices as proxy
• iOS and Android SDKs provide
the proxy libraries
• Amazon Cognito handles
authentication between proxy
and AWS IoT
• Enables use of OTA and AWS
IoT services
Amazon
Cognito
AWS IoT
Core

17. © 2020, Amazon Web Services, Inc. or its Affiliates.
Custom profile: Wi-Fi provisioning over BLE
• Provision Wi-Fi credentials over
Bluetooth LE using mobile device
• Save multiple networks,
reprioritize, add, delete
• Supports Bluetooth LE Secure
Connections (BLE 4.2 and up)
• Demo examples to get started

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Over-the-air updates (OTA)

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OTA updates
• Assign firmware update to groups using AWS
IoT Device Management
• Code sign new firmware images
• Validate signature on device
• Stream updates to device over MQTT or HTTP
• APIs to control installation and reboot logic
• Memory-efficient updated client

20. © 2020, Amazon Web Services, Inc. or its Affiliates.
OTA on FreeRTOS

21. © 2020, Amazon Web Services, Inc. or its Affiliates.
OTA actions
Developer
authors update
Upload to
cloud and sign
image
Schedule an
update job
Notify device
update is
available
Device
downloads
image (over
MQTT)
Write image to
flash
Close file and
verify signature
Notify
application that
new image is
ready
Application
activates when
it is ready
Verify image at
boot
Initialize OTA
agent and confirm
current image is
latest
Hand control to
application for
self test
On passing self
test, commit
new image
Update cloud
status to
completed
Developer
authors update
Upload to cloud
Schedule an
update job
Notify device
update is
available

22. © 2020, Amazon Web Services, Inc. or its Affiliates.
Getting started
Visit https://freertos.org/ for more information
• FreeRTOS kernel and libraries
https://freertos.org/RTOS.html
https://freertos.org/iot-libraries.html
• IoT Reference Integrations
https://freertos.org/aws-reference-integrations.html
• Community Forums
https://forums.freertos.org/
• Documentation
https://freertos.org/
https://docs.aws.amazon.com/freertos/

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Q&A
Tanmoy Sen

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Thank you!
Tanmoy Sen
Sr. Product Manager
AWS IoT
stanmoy@amazon.com