New ultra-low power Arduino board with built-in RF (RFM69)

Hi michaelkellett, we're looking into FCC but it's nothing something we are promising for a few reasons, including the elevated cost for testing. This still a very small scale product and any additional cost would make the end-price prohibitive for our target public. Also being a development board it can be used on so many ways which would simply void the certification. As mcb1 commented, the RFM69 module has some testing results for their product which cover the intentional emission component.

Cheers,
Mike M.

being a development board it can be used on so many ways which would simply void the certification

That arguement was used by Raspberry Pi until they finally submitted them for FCC testing and approval.

Your biggest enemy is the Australian Government who seem to have locked down every frequency.

Because of the power and easily adjustable settings of the RFM devices, it might be hard to get a worldwide type approval as the user can simply program whatever they want.

Most of the frequencies fall within the telemetry band, however we've seen that abused by people feeding continuous data streams.

Mark

Hi mcb1 sure when we hit the 5 millions units we'll have all our boards tested like RPI and Arduino . For the moment it's difficult to guarantee it'll be done for less than 500 boards. If you have a look on many Dev boards, including some from big manufactures it's not common to find the "FCC" logo on all.

Regarding the Australian Government, I don't consider to be the biggest enemy. I see it like any country to be honest. There are some frequencies/bands which can be used by any person in an open-class license arrangement so they can clearly specify what are the restrictions. A Dev board is like a car for me, I bet 99% of the cars can do almost twice the speed limit of any road, is up to the driver to use it within the legislation and don't do anything silly. Similar to that, I bet the Airport security will be very disappointed if you try to fly a FCC approved drone close to the runway.

Finally, I agree with you that some people might abuse on those open frequencies, like that bad neighbor that listen loud music at 3AM.

Cheers!

Mike M.

Hi!

This sounds great!

I wonder one thing: can you manage to sleep the arduino and wake it up by an incoming package of the RFM69? I imagine this would increase the battery life even more, no?

Thanks,

Francis

Using the various sleep modes is probably one  way of increasing the life of your batteries. If the chip supports an interrupt (any line will do that changes state when something of interest occurs will do)

but after reading a bit about the board

it is using a 16Mhz crystal, this means it could be unreliable at 3V3 see the chart showing safe operating speed vs supply, it may work on some boards but not others

Other ways of significantly reducing power is to slow down the CPU, how fast do you really need it to go ?, this of course is application dependent. but will also allow you to reduce the supply voltage. you need to consider the lowest voltage of the other parts though.

Don't listen to the radio the whole time, the datasheet indicates it consumes 16mA in listen mode... thats a lot for a AA battery. but of course, if you're not listening then you can't be woken up by the radio so you will need to use a watch dog timer

Transmit power could be limited based on the range you need. min is also 16mA but can extend to over 130mA...

Hey Francis,

There are a few options to preserve power and keeping the ability to receive messages over RF. The RFM69 module has a power-saving mode, which puts the Radio into a cycle Sleep/Awake until it receives a valid message, causing an interrupt which could be used to wake up the MCU, this sounds ok, but in practical terms the sender node might need to transmit the message multiple times until the receiving node is listening. Another option, which I personally prefer, is to use a pooling technique. The while "receiving" node+RF module are kept in sleeping mode and awakes from time to time, asking a master node (which is always on), if there's a message for to be received. I normally compare to the old days where we all used dial-up connections to download e-mails.

The Whisper Node is into production at the moment and a few practical tests showed some very nice figures related to the power consumption in sleeping mode: under 4uA for the whole board. More details about the board can be found at https://wisen.com.au/store/products/whisper-node-avr/

Robert Peter Oakes, you're right about the AVR atmega328p specification, where 16MHz is a bit off (around 3MHz over) the "safe operating zone". For general application I haven't had any issue running project at 16MHz @ 3.3V, including a board running for over one year inside my fridge transmitting open/close door, temperature and humidity. Anyway, in case you're developing a critical application or if you're planning to run your board on extreme temperatures there's always the option to reduce the MCU clock speed by configuring the CLKPR register. That's basically a CPU Clock pre-scaler and can be easily changed "on the fly" using the function clock_prescale_set ( clock_div_t x ) - http://www.nongnu.org/avr-libc/user-manual/group__avr__power.html.

The CLKPR register gets the initial value from the AVR Fuse CKDIV8 after boot and it's ok to change any time during your code execution. This is a great feature to save even more energy, and at the same time, speed-up your MCU when required. For example, you probably want full speed when talking to the RF module to save energy when having everything up at the same time. But you don't care much about how fast the CPU is if you just need to "blink an LED for 20ms" as 1MHz will be more than enough to do it.

Regarding the transmission power, the Radio offers RSSI, so you can self-adjust the output power to "just enough" instead of always using the max power. Here some simplified results from tests I've performed:

Cheers!

Mike M.

I thought that one of the many reasons to use an approved module was to simplify the passage of the complete device through the compliance procedure.

I'm not sure if it can in effect inherit the pass of the module in relevant aspects  or merely you can have a warm feeling that you are more likely to pass with such a module.

A company who's name escapes me has started selling a much more expensive competitor to the HopeRF devices whilst complaining that the current modules have such wide specs they couldn't pass EMC...All very interesting !

Looks similar to the Badgerboard

Hi,

I just got the lora version of the whisper node.

Were can i get an example of how to send and receive data from the lora network?

Thanks in advance