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Merged
merged 16 commits into from
Jul 30, 2020
Merged

Create example to send and receive messages with Azure #2

merged 16 commits into from
Jul 30, 2020

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LDong-Arm
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@LDong-Arm LDong-Arm commented Jul 22, 2020 •
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Introduction

Create an official Mbed OS example to demonstrate how to use the Azure SDK to communicate with an IoT Hub.

Note

  • This uses the MQTT communication protocol
  • The application runs on the main thread, while communication is processed in a dedicated thread internally managed by the Azure SDK
  • Azure's official iothub_convenience_sample is a reference for us. Its steps and API calls are very generic and standardised, so applications that use the SDK (including ours) couldn't differ much from it. In my opinion we may include Microsoft in the copyright header once we added, just in case.

Known issues

  • (Not happening anymore) On GCC_ARM the first message fails to send: 
    Error: Time:Wed Jul 22 15:33:15 2020 File:./main.cpp Func:on_connection_status Line:27 Connection failed, reason: IOTHUB_CLIENT_CONNECTION_BAD_CREDENTIAL
    subsequent messages are sent successfully
  • (Possible solution: Change get_timestamp() return type to int64_t to support ARMCC ntp-client#12 + retries) The shared access key to access IoT Hub relies on system time being correct. Many targets have no real time clocks, so we fetch time from an NTP server but this can fail sometimes. Please check the time printed is sensible, and reset to rerun the application as needed. A long term solution might be adding an option to use an X.509 key which does not depend on time.

Todo

  • Add copyright headers (TBC, subsequent PR) Done, Apache-2.0 license added
  • Support X.509 keys (future work)

@LDong-Arm LDong-Arm mentioned this pull request Jul 22, 2020
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@LDong-Arm LDong-Arm changed the title Create example Create example to send and receive messages with Azure Jul 23, 2020
LDong-Arm
LDong-Arm commented Jul 23, 2020
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main.cpp
Comment on lines +169 to +184
NTPClient ntp(_defaultSystemNetwork);
time_t timestamp = ntp.get_timestamp();
if (timestamp < 0) {
LogError("Failed to get the current time, error: %ld", timestamp);
return -1;
}
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This happens a lot. We'd better implement a retry but it would rely on ARMmbed/ntp-client#12.

LDong-Arm
LDong-Arm commented Jul 23, 2020
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evedon
evedon reviewed Jul 27, 2020
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A few minor comments

LDong-Arm added 4 commits July 27, 2020 17:22
@LDong-Arm
Create example to demonstrate sending/receiving messages with Azure I…
3ac2360 
…oT Hub client
@LDong-Arm
Improve Azure connection stability
f23c0dd 
Setting connection status callback *after* all other callbacks
seems to resolve connection failure on GCC_ARM, and it seems
like the standard thing to do in Azure's existing examples.

We also reduce the frequency to process Azure communication
stack from once per 1ms (default) to 100ms.
@LDong-Arm
Add README.md
72f862b
@LDong-Arm
Make IoT Hub tracing configurable and disabled by default
07cf407
LDong-Arm
LDong-Arm commented Jul 27, 2020
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@evedon Thanks for the review, I've addressed your comments. Also updated mbed-azure-client.lib so the license and copyright info are in place.

@LDong-Arm LDong-Arm requested a review from evedon July 27, 2020 16:28
@LDong-Arm LDong-Arm changed the base branch from master to development July 29, 2020 13:58
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LDong-Arm commented Jul 29, 2020 •
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Changed the base branch from master to development. This aligns with the new release model of Mbed OS official example.

@evedon evedon merged commit 4d053a1 into ARMmbed:development Jul 30, 2020
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@evedon evedon evedon approved these changes

@rajkan01 rajkan01 Awaiting requested review from rajkan01

@ashok-rao ashok-rao Awaiting requested review from ashok-rao

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@LDong-Arm @evedon