We created a minimum Lora implementation based on the RFM95 and the ATtiny85. The sketch that sends only outgoing messages, including encryption, on fixed channel and fixed SF is about 3.5 KB so we have plenty of room for extra’s. We have created a mini-PCB that holds the RFM95 on one side and the ATtiny on the other side, including a programming header. The PCB has some flexibility in the routing so you can decide on various ways to hook up the processor to the Lora transceiver and to use the remaining inputs for sensors (using JP1, JP3 and JP4). The minimum interface to the RFM95, existing of MOSI, CLK and NSS is in place and cannot be changed.
The 6-pin programming header interfaces to the 6 pin header on the Sparkfun Tiny Programmer.
Size is 22 x 22 mm and 8 mm thickness (in which the header accounts for 3 mm, so without header it would be 5 mm).
The pitch of all components is such that it can be soldered by hand, if you are not too unsteady
With this board you can reach sub 1 uA sleep current, allowing it to operate for years on a small cell. We use it for our own non-critical applications with just a single input, like a door contact, but we plan to make it available for the wide world as well.
We haven’t decided on pricing yet. If you are interested (either with or without components), pls send a mail to rene@iot-partners.nl
Correct, @arjanvanb that should be a little thing. ADR would be a bit more work. I wonder what KPN’s position is. On the one hand they would like maximum use of ADR since it optimizes their network capacity, on the other hand they themselves advise to switch ADR off for certain types of applications (like the non-stationary ones).
On my personal to-do list: I’d like to implement the MAC command LinkCheckReq in which the node can ask the network for the link budget. That would allow me to set SF and output power for a conservative link budget and thus save network capacity in a similar way to ADR. Do you know if there are any reference implementations that include this MAC commmand?
Very interesting, I’d like to try one for fun
I already got Mini Lora, may by Tiny Lora would be more appropriate for this one
you’re talking about small cell, what kind do you think about ? CR2032 or CR2450 ?
Hi @Charles, we have an application that does nothing more then send a few bytes to the network four times a day with SF12 and max power, that uses a Renata CR2430. I think it is 285 mAhr. We have calculated that it can run for 3 years. If you can use the deep sleep mode on the ATtiny with an external interrupt (like a door contact) you can go even a factor 4 longer!
If a fixed data rate is required, then SF10 would be better; hardcoding SF11 and SF12 is not allowed on a public LoRaWAN network, and you might get you a message from TTN on day.
Is any part of this CE and LoraWAN (pre)certified? It looks interesting for some of our use cases, but I don’t want our users to have to go through the whole certification process themselves .
@arjanvanb in fact for geolocation purposes KPN advises to send at SF12 with ADR off! They will probably come back from this statement when they have more traffic in their network
@Epyon No, this device is not certified. The RFM95 in itself is not certified, and it probably never will because it does not have the LoraWan stack on-board as the RN2483 has. So your own software needs to implement those features that are required for certification.
I don’t know in which country you are planning to use your nodes, and certification requirements may differ from operator to operator. For the Netherlands, KPN allows uncertified devices in the network as long as the series are small ( < 100).
@SunCobalt, this mini Lora board as presented in this thread is ready and available, but it has never been our prime goal to bring this to the market. We have many requests for simple applications, so we developed this mini board as a building block mainly for our own R&D. So if you are looking for a readily available product with for instance a magnetic switch that you can mount on your window or door: we are working on that but there is a long way from prototype to product in the shop
Wow I love the cleanlyness of this one.
I would be very happy if your software could be downloaded. Your implementation looks so much cleaner compared to what we did in the Junior IOT Challenge…!
Only if we could add GPS with libraries.
What about one i2c channel to talk to various sensors at the same time?
Oh, please apply one hole to the antenna pad so we can insert and solder one of those cheap curled wire antennas. In our balloon flight we used these and achieved a 350km+ distance. Very minimalistic at 15 cents each and good enough.
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