Best posts made by elcaron

While most of my home is made smart using ESP8266s, I plan to dive into MySensors for more energy critical stuff. The first project is a keyfob.

Attached is a first design for a 8-button keyfob mit hardware HMAC authentication via an ATSHA204, running on a CR2032 coin cell and fitting into a commercially available keyfob enclosure (see README on github repository).
The ATMEGA is supposed to run in power-down mode (400nA with disabled ADC, internal oszillator @ 8MHz), the powered down RFM69HCW should take 100nA in sleep mode and the ATSHA <150nA in sleep mode, so the overall standby consumption should be well below the self-discharge rate of the coin cell.
In standby, the buttons will have interrupts attached via PCINTx_vect, so that a button press will wake the ATMEGA.

Before I send out the PCB order, perhaps somebody is interested in having a closer look ... this is both my first MySensors project and my first low power project. Also, it is probably the most compact thing I have ever clicked together. (I am so glad about KiCAD's push and shove router ...)

Any comments? Tips? Ideas? Errors?
I would hate to send this to production and end up with 80 unusable PCB (Taking about PCBs, I will have a lot of spare ones in Germany, is anybody is interested ...)
The major issues I could currently think of are:

• Does MySensors implement the sleep mode of the ATSHA? Is it even possible in that package? I don't really know much about the chip (only followed the MySensors tutorial) and it would be a bugger if it sucked my battery dry ... - Answered: Yes it does.
• Will the coin cell provide enough current for transmission? I added a 22uF tantal, should I include more?

KiCAD project on github: https://github.com/kvoit/MySensors_SecureKeyfob/commits/master

Schematic: 0_1492625836524_MySensors_SecureKeyfob.pdf

I would suggest to get solder paste and a hot air gun (I have one of those 40$ thingys, which works fine after checking that it is not one of the units that have mains potential on the metal parts :D).
Maybe also stencils. I just had one made at jlcpcb for 7$ + shipping, it is still in the mail, though.
If you only have two left hands and no serious condition, that should make soldering them quite trivial.

If anybody cares, I have improved a few things - rgb led (choose the standard 505 that is used on RGB strips), impedance to antenna, button footprints ... It is all pushed to Github. There is also a branch with gerbers for a panelized version with v-cuts.
I will order it tomorrow evening. (Hint: I'll sit on 60 PCBs for this, soon. Location Germany.)

Oh, cool! That seems to be exactly what I was looking for. I'll add my projects as soon as I received them and tested them working. Thanks!

Can you link me to what the Github import function expects?

@mfalkvidd Thanks, that is what I feared. Then as far as I understand, it would be a really bad idea to move it away from D2, at least not to anything else than D3. But i guess when the ATMEGA is sleeping, the RFM69 will also be deep asleep, so there is nothing to expect from it to trigger PCINT2_vect. And D3-D7 on the same port is just enough for my 5-button keyfob, so I'll connect it to D2.

Haven't managed to do more tests today. Was trying to get a simple sensor + Gateway2MQTT config running, but the gateway just didn't receive any messages, despite the fact that Radiohead can use my RFM69HW hardware with at least 2.4GHz Wifi range. But let's not highjack my own thread I'll start a new one next weekend when I'll also try to run the personalizer without Wifi.

Answer to myself: There is one from Sparkfun.

Ok, my setup is running now (including personalization, encryption, and soft signing) and stuff is published to mqtt.
Thanks everyone for the help! I really like this community.

Now I need to resolve the issue with the OpenHAB binding but that's no topic for here.