MQTT with AWS questions


#1

Hi Chris,

thanks for our call today. As I mentioned, there are eWON topics we to need to address in the future. Could you please connect me with an IoT expert from your company to discuss feasibility and possible approaches?

Currently we use a basic script that sends live data from the eWON to AWS via MQTT.

Current situation:

  1. Data loss if internet is down
  2. We only send data from the eWON to AWS

Intended situation:

  1. After the internet was down the script sends the missing data locally logged on the eWON to the cloud autonomously
  2. Sending data both ways

#2

#4

Hi Alex,

Chris said you have some questions about the eWON and MQTT. What exactly did you want to know?

Kyle


#5

Hi Kyle,

Thanks for following up. I mentioned to Chris that we currently use a basic script that sends live data from the eWON to AWS via MQTT. There the things we want to improve in the future (please see below). Could you please give input on feasibility, possible solutions and possible support from HMS? (please see the current script in the attachment).


#6

#7

#12
  1. MQTT is primarily used to publish live data and as far as I know, this issue of data delivery and inconsistent mobile connections has not been addressed at the protocol level. I have seen some proposals, but for now this has to be done at the application level. There are some settings on the broker side for maintaining the session, but you would have to use BASIC or Java to create a buffer (possibly on an SD card) on the eWON itself. I am going to check with some developers to see if anyone has created a solution for this yet, but in the meantime, you can use historical logging and fill in the blanks with that data if it is critical.

  2. Currently you are only using the script to Publish messages, but you can also Subscribe to topics if you want to receive data using MQTT. See this doc. There are many other ways to send data from an AWS server to an eWON including the M2Web API, FTP, etc. The best way would depend on the type of data and specific situation.


#13

Thanks Kyle,

We’re looking into these options and we’ll write down our specifications more in detail. In general there is no need to limit the solution space to MQTT.

I’ve two questions already:

  • Which max. SD Card size does the eWON Flexy 205 support

  • How is the cost structure for M2Web API (Data Mailbox)?

Thanks,

Alex


#14

You can use an SD card up to 128GB. Please see this post for more info:

The m2web API and DataMailbox are free to use, but there are higher bandwidth and data limits with the Pro Account:

https://www.ewon.biz/cloud-services/talk2m/plan-pricing

Let me know if you are interested in speaking with our Solution Center which creates customized solutions for customers.

Kyle


#16

Hi Kyle,

Thanks for your message. The SD Card worked for me.

To me, the difference of m2web API and DataMailbox is not so clear. Do I understand correctly that m2web API allows me to access the data logged locally at the eWON? And the DataMailbox is a buffer in your cloud?

Further questions:

  • m2web API: is the bandwith stated on your website per eWON or per talk2m account?

  • m2web API: does it make sure that there is no data loss when the internet connection is down? (as long as there is enough storage on the eWON) If yes, whats the benefit of data mailbox?

  • DataMailbox data points: can a “rolling storage” be implemented that values are overwritten once it is full? Also, can it be expanded?

Thanks,

Alex


#17

Hi Alexander,

Do I understand correctly that m2web API allows me to access the data logged locally at the eWON? And the DataMailbox is a buffer in your cloud?

Yes, I think your understanding is correct and the DataMailbox essentially acts as a “buffer” for the data you are exporting.

is the bandwith stated on your website per eWON or per talk2m account?

The data bandwidth is per device and shouldn’t be an issue in most cases.

m2web API: does it make sure that there is no data loss when the internet connection is down?

The m2web API is just a programming tool to communicate with the ewon, it does not store data. I’m not sure I understand exactly what you’re asking.

whats the benefit of data mailbox?

The datamailbox is a central location where all of your data from various ewon devices can be extracted. It is a more direct connection and faster than having to download directly from the eWON.

DataMailbox data points: can a “rolling storage” be implemented that values are overwritten once it is full? Also, can it be expanded?

The datamailbox is essentially a buffer, like you mentioned, and data is automatically overwritten in a “first in first out” manner. It cannot be expanded or altered.

For more information, please see the DMWeb Programming page.

Kyle


#18

Thanks Kyle!

Is it also possible to write data (tag values) from a cloud via data mailbox to an eWON?

Best,

Alex