RFM12B board on Arduino with ethernetshield?

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RFM12B board on Arduino with ethernetshield?

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aetjansen

Hi All,
After a few projects with Arduino's, I would love to get my feet wet with JeeNode's. The low-power wireless properties are very attractive to setup a WSN around the house.
However, I already have an arduino with an ethernet-shield and an xbee shield attached. I am not too familiar (yet!) with protocols like I2C and SPI, etc, and I have a bit of trouble figuring out if it would be possible to at the new RFM12B board to the existing setup. If possible, that would enable my gateway-unit to be extended with a communication option for JeeNodes.
I use the gateway unit currently to receive Xbee data and post it to a server online.
The Xbee shield used D0 and D1 (serial tx,rx) ports, and the ethernetshield uses pins also in use by the rfm12b board (D10-D13). Would it be possible to add the RFM12B board as well and still use the xbee and ethernet capabilities?
Kind regards, Arno Jansen

Posted 03/03/2011 22:09:03
jamescw

BUMP!
Is also like to know how todo this.

Posted 08/03/2011 15:00:03
tankslappa

One problem you have is that the RFM12B runs on 3.3v, the Arduino on 5v. One solution would be to change the Arduino to run at 3.3v by changing the regulator, but I have no idea if the xbee and ethernet board would like this, so you'll probably have to build a little resister voltage divider for all the input lines to the RFM12B (not the output lines though).
Next problem is the SPI connection, the ethernet is already using those. You should be able to put the RFM12 onto the same MISO, MOSI and SCK lines, but you will have to use a different line for the select (SS). The RF12 library expects the select to be on D10, you'll have to move it to D9 and change the RF12 library definition of SPISS. The interrupt onto D2 looks free.
So with the voltage divider and select line moved you should be connected up hardware wise...
Unfortunately there is one last problem, with the Xbee and ethernet, is the Arduino going to be too busy to service the RFM12B fast enough to keep it happy? No idea! You'll have to try it!
If that is an issue, then JC sells his own Ethernet board implementation for the JeeNode, so you could connect one of those to a JeeNode and use that as the RFM12B to ethernet bridge.

Posted 08/03/2011 17:45:42
tankslappa

Oh, and don't forget a regulator on the power to the RFM12B!

Posted 08/03/2011 22:55:04
jcw

@tankslappa - the RFM12B board has level adjustment resistors.
You're going to need 5 I/O pins: MOSI, MISO, and SCK are standard SPI signals which can be shared across multiple chips. The RFM12B also needs a chip select pin (it uses SS/digital10 on the JeeNode) and an interrupts pin (digital2 on the JeeNode). That last one is tricky - the JeeNode uses the highest-priority interrupt pin, since these interrupts come in at a fairly fast rate while "on-air". If you use a different pin, you'll need to adjust the RF12 driver in several places. The chip select pin is defined as SPISS in RF12.cpp.

Posted 09/03/2011 00:03:21
tankslappa

@JC, ah yes, the penny didn't drop, I forgot about the "new" RFM12 board, I thought the OP was playing with a bare RFM12B module.

Posted 09/03/2011 01:11:32
jamescw

I've been looking at the EtherCard at it looks like some significant work took place to make another SPI device work along side the RFM12B.
The RFM12B driver looks like it was left unmodified to accommodate the ether card, but the ether card driver had to be modified to use a different SPISS pin and lock out interrupts from the RFM12B.
I've got the RFM12B board working with the Arduino as my base-station for my WSN, the Arduino is hooked to a small pc via USB. I now want to use Ethernet to completely remove the PC from the set up.
I now have two options, I either buy an Arduino EtherShield and attempt to modify either the RFM12B driver or the ethernet driver to make them work together (not so confident on that one) or invest in another JeeNode plus CarrierBoard w/ box and an EtherCard to achieve what a want. The later option is probably twice as costly but is probably the fastest, but it would be a shame to not use my existing kit.
Any thoughts from the experts?

Posted 09/03/2011 11:21:54
jamescw

After reading this: http://arduino.cc/en/Main/ArduinoEthernetShield
I think it maybe simple todo is some scenarios...
"The solder jumper marked "INT" can be connected to allow the Arduino board to receive interrupt-driven notification of events from the W5100, but this is not supported by the Ethernet library. The jumper connects the INT pin of the W5100 to digital pin 2 of the Arduino."
So by default, it is NOT connected to the same interrupt pin!
So theoretically if you change the SS pin in the RFM12B driver to another pin, you should be able to use both devices together, with RFM12B taking priority.
This should be far easier then messing with RFM12B's interrupt pin, but it does mean the Ethershiled cannot be interrupt driven (not supported by the default library anyway).
Can anyone test this? (I havent got my ethershild yet)

Posted 09/03/2011 15:16:20
warp

I would also be interested in this project, this is exactly what i want to do.
So if someone could give feedback....if not i will try by myself, but i first have to buy 2 RFM12B ;-)

Posted 10/03/2011 10:19:22
aetjansen

Thanks for the replies people, greatly appreciated.
I am not yet very familiar with the inner workings of SPI, but judging by the pins used on the Xbee shield and the ethernet shield I have already connected to the Arduino, it should be possible to use an RFM12B board with some trial an error.
Not having interrupts on the ethernet shield is not an issue for me since I do not plan to run a server on the arduino. Instead, the device will pull in data from online if need be (a web interface changing config settings, storing those on the server and the arduino periodically checking on the server for new settings).
The D2 interrupt pin (on ethernet shield v4, D4 on v5) is used to access the SD card if I am correct. However, my shield does not look like the v5 (pcb wise), but has no SD card, so it might not even use those pins right now.
@tankslappa I was indeed talking about the JeeLabs RFM12B board, but I do not yet have one.
I guess I would be best off using one wireless technology for the projects around the house. And to be honest, it seems to me that JeeNodes are the way to go (as opposed to Arduino's of which I got a few to get me started on programming MCU's and electronics). I will have to use those in other projects than ;-)
Thanks for the advise! And if anyone does manage to get this setup going, please do not hesitate to share your experience..
Regards, Arno

Posted 10/03/2011 12:02:21
gentor

... a possible solution:

Posted 11/03/2011 11:10:43
aetjansen

Wow, very impressive work gentor and most of all: thanks for sharing your solution in such great detail! Judging by the amount of "yeah, I would like this too" posts, I think you made quite a few people happy :-)
For my original question this would work as well as I would like to add an already existing Xbee to the setup you posted. That should not be a problem as the Xbee uses D0/D1 for serial communication and does not interfere with the SPI used by the RFM12B and ethernet shield.
Physically however, adding the RFM12B board to the stack of Arduino-Ethernet shield-Xbee shield, would probably not fit (judging by the picture you posted) as the Xbee shield is an odd form of shield (I am definitely not a fan) and blocks those pins used by the RFM12B board (http://www.shieldlist.org/libelium/xbee).
It might fit though if an 8 pin header is stacked on the exposed header of the ethernet shield. Or, use a different Xbee board (I like the Adafruit one: http://www.adafruit.com/xbee).

Posted 11/03/2011 12:36:47
jamescw

Nice work gentor, will this work with the most recent Ethernet Shield?
I would put this on the wiki if you can, this seems to be hot topic lots of people have been trying todo this, myself included.

Posted 11/03/2011 17:27:30
gentor

It works with Ethernet Shield 1.0... I can try with most recent Ethernet Shield if this is useful to someone;
but take into account that new Ethernet Shield should be the simplest case because it has not problem with multiple SPI device...
I'm very happy to put this layout on the wiki, let me know if you need more information !

Posted 12/03/2011 11:54:17
jamescw

If you have the most recent Ethernet Shield, it would be very useful for everyone to know that it also works with that.
Im still waiting for mine to come in the post, and I suspect people will buy the most resent one if they are attempting todo this.

Posted 13/03/2011 12:18:05