Battery based atmega328p sensor with SMD nrf24l01+

[openhardware.io]

https://www.openhardware.io/view/46/Battery-based-atmega328p-sensor-with-SMD-nrf24l01

[GertSanders]

Added BOM, EAGLE files, board image and a warning: untested board !

[bisschopsr]

Hi Gert,
Looks like an interesting design. Would be great if you could add the schematics as PDF (for the no- eagle users)

Thx

Ralph

[GertSanders]

@bisschopsr

Done

[bisschopsr]

Thx Gert. Very helpful!

Ralph

[alexsh1]

@GertSanders I think I may struggle with capacitors (100nf) as there are a few under the IC this time. I have the following ones:

http://www.ebay.co.uk/itm/100nF-Ceramic-Disc-Capacitor-x10-/111609062446?hash=item19fc6b242e:g:iZMAAOSwBLlU8FK-

Which ones are you using please? Do you think these would be ok:

http://www.ebay.co.uk/itm/SparkyLabs-multilayer-100nF-0-1uF-ceramic-capacitors-various-quantities-10-/181288374594?var=&hash=item2a35a11142mEo7ZMWSQSd4VxrmTONg4dg

OR perhaps I should use 0805 SMD ones?

[GertSanders]

@alexsh1

I'm using these:

http://www.aliexpress.com/item/100pcs-Multilayer-ceramic-capacitor-X7R-100nF-0-1uF-104-50V-2-54mm-10/2000733997.html

Any 100nF capacitor which fits inside a 100 mil footprint is fine. Maximum height should be 4mm.

[alexsh1]

Ok, clear now. I have been really struggling with two ceramic 22pF capacitors in V2 node

[GertSanders]

My prototype boards for V3 have finally arrived. This weekend I will start assembling and testing. Alexsh1 has already confirmed that the drill size of JP1 is a bit too narrow for standard breakable 2.54mm spaced headers. Mine do fit, but just barely. Version V4 of this board is already uploaded to OSH Park, but not yet tested. On that I used another library for the headers which has larger holes.
So I will put that version available, version 3 is just for testing.

Another comment: if the 3V3 regulator is not mounted, do not forget to bridge the "3V3" solder pad.

And also: this board is made for battery holders with 2 batteries, not possible to mount two individual AAA battery holders any more.

[alexsh1]

@GertSanders Can you please summarise the difference between V3 and V4 please?

[GertSanders]

@alexsh1
In V3 I had two optional pull up resistors for pins D2 and D3.
In V4 I only have 1 pull up resistor for D2. But I gained space to add extra pins so that I have the 6 pin ISP layout included in the extention connector.
All the rest remained the same.
I uploaded the schematic to Openhardware.io (I think).

[alexsh1]

I have just noticed you have the INT solderpad. What is it for please?

[GertSanders]

@alexsh1
This is in the V3 version only.
That solderpad allows you to connect the INT pin on the NRF24L01+ to pin 2 of the ATMEGA328p. IF the software would allow it, you could then have the radio wake up the atmega328 via a hardware interrupt.

This is not used in MySensors, but could be used for direct communication via the RF24 library.

This solderpad is available in v3, but I removed it from v4, because I also do not use this interrupt capability in my sensors (all based on MySensors library).

It would make sense if the connector would allow an RF6x radio, but the SMD version has a specific connector layout, so no point to cater for possible INT use in my view.

[alexsh1]

@GertSanders Thanks - I was wondering why you had it as it is not supposed by MySensors, but knowing your "board style" this hardly should come as a surprise - you really try to account for any eventuality.

EDIT: Was just browsing the boards looking for a new board for the GW.
I think its time to publish your board under the name of Gertino or something
Just an idea

[alexsh1]

@GertSanders Did you try EEPROM or ATSHA204a? I have got AT25512N-SH-T SOIC-8 which is slightly different one compare to your BOM and I wonder if this would be fine.

I also have a few 8 pins ATSHA204a, but they are not suitable for MySensors and 3 pin version is in post.

[GertSanders]

@alexsh1

Nope, I did not yet try the Flash memory, nor the ATSHA204. I did received some three-pin versions recently, so I could try. But my gateways is directly a raspberry, not an atmega328 based one, so signed messages are not (yet) supported. For flash memory I'm in the same predicament as other contributors here. I can buy them from Mouser , but 20 USD for transport kills the idea of buying only 5 pcs.

I would like to participate in a group buy. Maybe an idea for the meetup in Breda next month.

[alexsh1]

@GertSanders Count me in for a group buy - excellent idea

Do you think the IC I have (AT25512N-SH-T SOIC-8) would be working with your board?

[GertSanders]

@alexsh1
Really no idea. Someone with knowledge of the dual-optiboot workings should be able to confirm this.
I have some Winbond flash memory, but did not yet have time to do a test yet (other projects are asking for priority).

[alexsh1]

@GertSanders ATSHA204A is working fine on your node. I finally have built a full node with ATSHA204A and SPI EEPROM.

Starting sensor (RNONAA, 2.0.0-beta)
Radio init successful.
Pressure Sensor1.1isMetric: 1
send: 12-12-0-0 s=2,c=1,t=38,pt=7,l=5,sg=0,st=ok:3.40
send: 12-12-0-0 s=255,c=3,t=0,pt=1,l=1,sg=0,st=ok:114
send: 12-12-0-0 s=255,c=4,t=0,pt=6,l=10,sg=0,st=ok:FFFFFFFFFFFFFFFF0300
Signing required
send: 12-12-0-0 s=255,c=3,t=15,pt=0,l=2,sg=0,st=ok:


Waiting for GW to send signing preferences...
Skipping security for command 3 type 15
read: 0-0-12 s=255,c=3,t=15,pt=0,l=2,sg=0:

Mark node 0 as one that do not require signed messages
Mark node 0 as one that do not require whitelisting
send: 12-12-0-0 s=255,c=0,t=17,pt=0,l=10,sg=0,st=ok:2.0.0-beta
send: 12-12-0-0 s=255,c=3,t=6,pt=1,l=1,sg=0,st=ok:0
Skipping security for command 3 type 16
read: 0-0-12 s=255,c=3,t=16,pt=0,l=0,sg=0:
Signing backend: ATSHA204
SHA256: A8457C04B9E7BAD1DC89908CB0127583D783B5-�¶
Transmittng nonce
send: 12-12-0-0 s=255,-�ÖÖ139
Current nonce: A8457C04B9E7BAD1DC89908CB0127583D783B54D5B963B84E9AAAAAAAAAAAAAA
HMAC: 78E50639CF4048466816DD0CD92E3B21BF--�j-�]
Signature OK

[GertSanders]

@alexsh1
Excellent !!!

[vikasjee]

@alexsh1 Can you please publish your full node design (SCH+BRD) or/and PDFs with ATSHA204A and SPI EEPROM? I am really interested in checking it out! Also the relevant sketch to understand how the battery operations are really supported esp. with interrupt handler et al.

[GertSanders]

@vikasjee
Alex used the hardware described at the start of this thread.
You will find all design documents on Openhardware.io