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Topic: Available shields and shield ideas (Read 7 times) previous topic - next topic

vxir

Well, using the module won't be as fun :-(, but it will be a lot more likely to actually work :-)... but it does make the problem a LOT easier!

Anyone have an issue with the fact that its 3.3v?  It does not look like the pins are 5v tolerant.  So to expose the arduino pinouts at 5v we'd have to use the CPLD I've been talking about.  We could push all the Arduino pinouts into the CPLD, and then connect the CPLD to this module.  So you could actually reprogram the CPLD to remap the arduino pinout to the 1281 pinout. That will be fun! :-)

Given that there are a lot fewer pins on the 1281 then on the 1280, I'm wondering if there will be enough to push out to the arduino pins... we'll have to check to see if all CPU pins are exposed or if some are used within the module.

Finally, my major concern is that they seem to be operating the CPU at 4mhz.  Anyone else see issues with that?




novice

#46
Oct 13, 2009, 06:50 am Last Edit: Oct 13, 2009, 07:49 am by novice Reason: 1
@vxir
Quote
It does not look like the pins are 5v tolerant.

The datasheet states:
   GPIO Output Voltage (High/Low) -10/ 5 mA 2.3/ 0.5 V

Looks like you're right.  I assume they've gone for lower voltages to minimise power/battery usage.  Microchip and Freescale modules use similar voltages.

Taking a look at the AT86RF230 Transceiver again, its power supply voltage is 1.8V to 3.6V (with Internal Regulator).

"Supply voltage VDD Min Max Typ
                                 1.8  3.0  3.6 V"

novice

@vxir
Quote
Given that there are a lot fewer pins on the 1281 than on the 1280, I'm wondering if there will be enough to push out to the arduino pins... we'll have to check to see if all CPU pins are exposed or if some are used within the module.

Considering Inopia is the initiator of these ideas, he'd have to provide his opinion.

If the 1280 is more suitable then possibly choose to implement an Atmel AT86RF230 Transceiver and 1280 mcu on your own board with the board antenna discussed previously.

Inopia's main functional requirements appear to be:

- "I'm looking mostly for arduino<->arduino communication. I want to build a network of several arduino mega based sensor nodes that form an ad-hoc, multi-hop wireless network"

- " I want something that's cheaper and with a bigger MCU (32kB program flash is not enough for our purposes)."



Inopia - when you say "arduino mega based sensor nodes" do you mean every node has an Arduino Mega attached?. Or that each uses a mega mcu?.

Inopia

I'm perfectly fine with it being 3.3v. As for the 1280 vs 1281 and clock speed issues, all is fine with me as long as it has 128k program flash and at least 4k ram. 4MHz is fine for me because I want the thing to be in low power mode 99.9% of the time anyway.

The modules come in various forms with different antenna solutions (dual chip, trace, connector), and http://shop.strato.de/epages/61427429.sf/en_GB/?ObjectPath=/Shops/61427429/Products/630000003 sells them for <12 euro/piece with no minimum qty.

Arduino compatibility isn't a huge thing for me personally, but since the modules don't have all the Atmega1280 pins broken out it won't be possible as far as I can tell to make it arduino compatible. For one, PORTA on the atmega is 8 pins that can work as ADC. To be fully compatible with the arduino they should all be connected to the header on the lower left hand side of the board (decimilia with the USB facing up). Since those modules only have 4 ADC pins broken out I see no way to make this work. You could still go with a 'somewhat' compatible board that at least does SPI/power/digital I/O, so that you can stick on an ethernet or LCD shield, or battery packpack.

I think the ideal solution in terms of technical specifications would be to take the arduino mega design and replace the MCU with one of those ATmega1281 + RF chips. In terms of cost and ease of design I think a (partially) arduino-compatible break out board for the module would be a great solution as well.

Inopia

Quote
Inopia - when you say "arduino mega based sensor nodes" do you mean every node has an Arduino Mega attached?. Or that each uses a mega mcu?.


Either I suppose. It could be an arduino mega with some sort of wireless shield, or an arduino with a wireless chip on-board.

vxir

I have fear that they can only drive the chip at 4Mhz because the 230 is so sensitive to digital interference that it can't handle higher clock rates...

Eric T

I've created a shield board that will be available sometime in November 2009. It is a video overlay board that uses the MAX7456 chip from Maxim. I've not determined pricing yet, but once I have I'll add it here and update my site.
Here is more information about the board:
http://lowvoltagelabs.com/products/videooverlayshield/

Thanks,
Eric
Low Voltage Labs

novice

@Inopia
Quote
Inopia - when you say "arduino mega based sensor nodes" do you mean every node has an Arduino Mega attached?. Or that each uses a mega mcu?.

Either I suppose. It could be an arduino mega with some sort of wireless shield, or an arduino with a wireless chip on-board.

Sounds like you have to decide.

Satisfying your 2 original Requirements, points towards each node using an Atmel mega mcu and capability for one to interface to an Arduino Mega at the 'Main' node to interface to a computer.
Having each node consist of an actual Arduino Mega would be too costly.

Do you envisage a board with mcu, transceiver, antenna, power supply connector, header (for local sensors), and some means of interfacing to an Arduino Mega (on the main node) - presumably UART?.

mowcius

Quote
I've created a shield board that will be available sometime in November 2009. It is a video overlay board that uses the MAX7456 chip from Maxim. I've not determined pricing yet, but once I have I'll add it here and update my site.


I had seen that and I thought that I had added it to the list already but apparently not... It looks good.
I will be buying one of those, It would also be a good prank board!

Mowcius

Inopia

Note that the AT86RF230 + an avr such as the 128 is essentially Atmel's Zigbit offering. The RF chip is just a simple packet radio, all the zigbee stuff (routing, etc) is handled by the avr. The zigbit software stack isn't open source afaik, but I could be wrong. Personally I'm interested in developing my own routing protocols so not a big issue for me.

As I see it there are three options so far when it comes to using this chip:

* An arduino shield with just the RF chip. The bundle arduino mega + shield would then essentially be a zigbit module.
* A break-out board for the avr+rf modules. Should be cheap to produce, but can't be fully compatible with arduino shields because not all the neccesairy pins are broken out. The modules are dirt cheap, so I think it is a compelling option in terms of cost. It does run at 4MHz apparently so this might be a bit slow for some.
* A completely new Arduino board, using the Arduino Mega as a template but using an ATmega128RZAV (ATmega 1281 + RF) instead of a vanilla ATmega 1281.

Any of the above would be fine for me, so I'll let your electrical engineers tackle the design bit.

Link to modules: http://shop.strato.de/epages/61427429.sf/en_GB/?ObjectPath=/Shops/61427429/Categories/ZigBee/%22ATMEL%20ZigBit%22/%22ZigBee%20Module%22
Link to all-in-one chips: http://www.atmel.com/dyn/products/product_card.asp?part_id=3949

novice

@Inopia
Quote
Personally I'm interested in developing my own routing protocols so not a big issue for me.

Why not use Zigbee?.

Inopia

Because Zigbee is boring :3

I would like to use this hardware for sensor networks research. There are many different types of networks that you can build such as multi hop collection trees, multi hop or single hop many-to-many routing, etc. Parameters such as power consumption, bandwidth, burstiness, and network density all influence how well a protocol performs. Then there are different metrics for deciding what constitutes 'good'. This can be delivery rate, power consumption, resilience to churn, dealing with mobile nodes, resilience to interference from other networks, etc. Finally you could look at things like reducing overhearing and contention by using multiple channels, indoor localisation (fingerprinting), etc.

novice

@Inopia
I figure you're either in the military or academia. They're always re-inventing the wheel.  ;D

Zigbee may be "boring" as you see it, but that's where the Wireless Sensor Networks are heading.  I suggest that your cheap node implementation be at least Zigbee compatible so it is marketable.

You can separately load your own customised stacks as you wish.

Inopia

@novice: if it wasn't for academia there wouldn't have been Zigbee in the first place.

Why don't you get an xbee shield if you want Zigbee?

vxir

@Inopia: can you open source your work so our little device will have some pretty cool sensor network infrastructure?  Or are you working behind an iron curtain? :-)  I'm interested in cooperative robotic, formation flying RC airplanes, etc so the kind of advanced sensor network that you are talking about is an essential building block.


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