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PostPosted: Tue Nov 17, 2015 1:45 pm 

Joined: Tue Sep 01, 2015 8:31 pm
Posts: 24
Location: Paris, France
Hi JP,
I got my hands on STM32L1 Nucleo board: http://www.st.com/web/catalog/tools/FM1 ... oL152RE-pr, alongside with Nucleo Spirit1 add-on board: http://www.st.com/web/en/catalog/tools/PF261982

I am planning to try your OpenTag (https://github.com/jpnorair/OpenTag) on this set-up. I have two boards like this.

My question is - is it possible to use SPIRIT1 in 868MH range, or I have absolutely to buy 433MHz module?

Point is that these X-Nucleo Spirit1 add-on boards are only ade in 868MHz and 915MHz variants (http://www.emcu.it/Wireless/SubGHz/Sub1Ghz.html), so I do not know where to get the 433MHz module only add-on board... Maybe in that case I would have to buy something like this: http://www.st.com/web/en/catalog/tools/PF258711

BR,
Drasko


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PostPosted: Tue Nov 17, 2015 7:36 pm 
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Joined: Tue Jun 12, 2012 4:33 am
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Location: New York, NY
868 MHz should work, it just needs new register settings in the firmware. Most of these are already written, they just need to be exposed by uncommenting an #define in the radio header.

Also, a new board file needs to be created to map the I/O between STM32L and SPIRIT1 with these PCBs. That is a small job, though. Also, for OpenTag you will need the 32.768kHz oscillator attached. You will need to solder one to the Nucleo board along with matching caps -- it doesn't come with this.

So now I'm interested in this platform.
http://www.findchips.com/search/X-NUCLEO-IDS01

I will buy a couple and add official support before the end of the year. I will use the 915MHz version because I'm in USA, but 868 and 915 versions will be supported.


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PostPosted: Tue Nov 17, 2015 7:57 pm 

Joined: Tue Sep 01, 2015 8:31 pm
Posts: 24
Location: Paris, France
Quote:
Also, a new board file needs to be created to map the I/O between STM32L and SPIRIT1 with these PCBs. That is a small job, though. Also, for OpenTag you will need the 32.768kHz oscillator attached. You will need to solder one to the Nucleo board along with matching caps -- it doesn't come with this.


Can you please explain me in some more details - why this additional oscillator is needed?
Also, can you please give some schematic instructions so that I can see the design - how to add components.

Quote:
So now I'm interested in this platform.
http://www.findchips.com/search/X-NUCLEO-IDS01


I have a really great experience with Nucleo line. They are reliable, well done boards. I thin that STM32L1 Nucleo + this SPIRIT1 add-on can really be a GREAT strting point for OpenTag and DASH7. Boards are cheap and well supported - if we add the documentation we can really popularize DASH7 more.

I am willing to work on this platform and my first work will be to enable 868MHz, since I am in Europe (Paris, France).

I would ike to make a proof of concept - several Nucleo nodes + one GW, probably Linux based - but I am still struggling to understand how DASH7 gateways are made. I have in my head some wide area deployments:
1) A base-station similar to some LoRa GW (like this for example: http://www.kerlink.fr/en/products/lora- ... on-868-mhz)
2) number of end-nodes

I guess that 3km perimeter can be covered, and if this is the case, then a project like this one: http://thethingsnetwork.org/ can be organized, only for DASH7. I guess topology like this can cover whole city, only that you will use twice the gateways than LoRa - but they can be 3 times cheaper.

Does this sound realistic to your, or am I too optimistic?

BR,
Drasko


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PostPosted: Tue Nov 17, 2015 8:08 pm 
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Joined: Tue Jun 12, 2012 4:33 am
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Location: New York, NY
LoRaWAN is full of missing features -- like good 2-way communication. Maybe I'll look at their platform (the things) and see if I can port DASH7 into it, to work together with LoRaWAN. LoRa reference design also uses STM32L, so it should be really easy.

To replicate this network with SPIRIT1, I think the best frequency is 169MHz. SPIRIT1 is optimized for narrowband, and to have good narrowband performance in urban environment, the frequency should be low. but it's fine to test first at 868/915.

Take a look at your nucleo board and just make sure that it has a low frequency oscillator (32.768 kHz). Mine did not have these, I had to add them. RTOSes for wireless need precise clocks in order to schedule communication intervals, so you need the precise timer from 32.768 kHz crystal. You can look at the Saturn schematic to see a crystal and capacitor pair that will work. https://github.com/jpnorair/Saturn


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PostPosted: Tue Nov 17, 2015 8:33 pm 

Joined: Tue Sep 01, 2015 8:31 pm
Posts: 24
Location: Paris, France
Quote:
LoRaWAN is full of missing features -- like good 2-way communication. Maybe I'll look at their platform (the things) and see if I can port DASH7 into it, to work together with LoRaWAN. LoRa reference design also uses STM32L, so it should be really easy.

To replicate this network with SPIRIT1, I think the best frequency is 169MHz. SPIRIT1 is optimized for narrowband, and to have good narrowband performance in urban environment, the frequency should be low. but it's fine to test first at 868/915


I was not thinking about using Nucleo with OpenTag as a node for LoRaWAN network. I was thinking more about creating an urban DASH7 network from the scratch.

That means:
- nodes with Nucleo
- Gateway

Node architecture is more or less clear - OpenTag on Nucleo with SPIRIT1.

Now I am trying to figure out how Gateway should look like - should it be Linux machine with SPIRIT1? How many simultaneous connections can it handle (i.e. how many end-nodes can be connected to one base station)? What is the expected range (can we reach 3-5km in urban environment)? Etc...

BR,
Drasko


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PostPosted: Tue Nov 17, 2015 8:37 pm 

Joined: Tue Sep 01, 2015 8:31 pm
Posts: 24
Location: Paris, France
Quote:
Take a look at your nucleo board and just make sure that it has a low frequency oscillator (32.768 kHz). Mine did not have these, I had to add them. RTOSes for wireless need precise clocks in order to schedule communication intervals, so you need the precise timer from 32.768 kHz crystal.


I can see here: http://www.st.com/web/en/resource/techn ... 105823.pdf

Quote:
5.6.2 OSC 32 kHz clock supply
There are three ways to configure the pins corresponding to low-speed clock (LSE):
• On-board oscillator: X2 crystal. Please refer to the AN2867 for oscillator design guide
for STM32 microcontrollers.ABS25-32.768KHZ-6-T manufactured by Abracon
corporation.


It seems like Nucleo boards have this oscillator already integrated.

BR,
Drasko


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PostPosted: Tue Nov 17, 2015 8:45 pm 
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Joined: Tue Jun 12, 2012 4:33 am
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Location: New York, NY
You need the LSE crystal on X2.


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