Author Topic: Making a lower power Moteino  (Read 25891 times)

joelucid

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Re: Making a lower power Moteino
« Reply #45 on: April 25, 2016, 09:17:16 AM »
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We should split this topic, what's a good starting post to do that?

Seems to me all but the very first message are off the original topic. Speaks to our forum discipline :-)

I think you could separate right there.

In terms of specs I would think:

a) Eliminate the regulator
b) Eliminate the resonator
c) Potentially switch to 328pb

Then comes the timer question. Part of this is being able to run lower power than with the WDT or listen mode. And part of it is being able to track time more precisely. I think some options are:

1) tpl5010 - super simple, super small, very low power timer. Not precise.
2) am1815 - super low power RTC, not temp corrected.
3) 32.768khz crystal on 328p - this gives you a precision timer at <1uA. But a lot needs to be done in software.

1) could probably just take the place of the regulator given how small it is. Same for 3) and the resonator. If you want to add 2) you probably need to let go the flash - it wouldn't hurt me, I've never had much use for it.

With 1) or 2) you'd have the lowest power arduino clone on the market. At least last time I checked nobody had that.

I think 2) is more attractive overall. But it has the difficult package issue.

I guess another thing to consider is throwing in a si7021 at least as option. Everybody should have a handful TH motes at home and it would be great to have something less expensive than the Moteino + Weathershield option available.

Joe

SadE54

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Re: Making a lower power Moteino
« Reply #46 on: April 25, 2016, 09:59:34 AM »
What are the benefits of the atmega328pb over 328p ?

joelucid

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Re: Making a lower power Moteino
« Reply #47 on: April 25, 2016, 10:11:24 AM »
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What are the benefits of the atmega328pb over 328p ?

Cheaper and more peripherals.

SadE54

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Re: Making a lower power Moteino
« Reply #48 on: April 25, 2016, 10:37:00 AM »
I looked at the datasheet . Seems nice : 3 16 bits counters !  ;)
I guess this one is not officially supported by the Arduino platform ?

WhiteHare

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Re: Making a lower power Moteino
« Reply #49 on: April 25, 2016, 12:03:43 PM »
FWIW, I'd like to see an am1815 on a Moteino.  It's one of the flagship lowpower RTC's, and it has a small footprint.  It's also difficult to hand solder.  I think those qualities taken together might help some people justify buying a pre-made board (i.e. buy rather than make).

Felix

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Re: Making a lower power Moteino
« Reply #50 on: April 25, 2016, 02:02:38 PM »
@joelucid,
RE the MCU:
a) and b) are no problem. This would imply different fuses also. Maybe fuses should also be discussed.
c) This will likely not be a reality due to lack of support. When I switch to 328pb it will be everything I make.

RE the timer:
Unfortunately am1815 cannot be sourced from any major reputable distributors. The RTC is available here.
32k crystal + lots of work also probably not a good option. Simple is still a feature i'd like to keep.

Si7021 could be included. The 4MBIT FLASH may also be optional, regardless of anything, having memory is attractive to lots of people.

- We should also start talking about battery.
- We should also start talking about board format, layout, pinout, perhaps battery connections depending on the battery.
- We should also start talking about programmability (ISCP, FTDI) and powering it when attached to a FTDI. I am thinking it should only be able to work when its own power supply is attached (ie battery), since the 5V from FTDI will fry it (no regulator) - the FTDI also has a 3.3v power output (via solder jumper) but it's limited to 50mA so that won't do it either.
« Last Edit: April 25, 2016, 03:09:29 PM by Felix »

joelucid

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Re: Making a lower power Moteino
« Reply #51 on: April 25, 2016, 02:40:08 PM »
Felix, I'll have more on the other items later. Just quickly: the am1815 is broadly sold by Abacon as ab1815. Digikey, mouser etc all carry it. It's fairly inexpensive and VERY low power.

Felix

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Re: Making a lower power Moteino
« Reply #52 on: April 25, 2016, 03:16:26 PM »
Felix, I'll have more on the other items later. Just quickly: the am1815 is broadly sold by Abacon as ab1815. Digikey, mouser etc all carry it. It's fairly inexpensive and VERY low power.
Doh, I just searched to AM1815 so of course I got nothing. AB1815 reveals it. Thanks for pointing that out. At $1.95 (1qty) it's quite a pricey part compared to other things. The required crystal adds another $0.70.
In 1000qty this combo would come to $1.31, not bad.
Which of the AB18X5 variants would be preferrable? I2C or SPI?
How about the more package friendly (still pretty low power at 1uA) MCP7951x/MCP7952x?
« Last Edit: April 25, 2016, 03:25:05 PM by Felix »

joelucid

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Re: Making a lower power Moteino
« Reply #53 on: April 25, 2016, 04:11:38 PM »
I've used i2c but realized that spi would have been much better: when you have an rtc the temptation is to use it listen mode style. That means setting a couple of registers every other second or so. And with i2c that takes too much time/power.

I think 1uA is too much these days for simply keeping the time.

Felix

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Re: Making a lower power Moteino
« Reply #54 on: April 25, 2016, 05:07:33 PM »
Right, so it sounds like the 1815 variant.
1uA is too much yes, when 15nA is an option :)
That and the fact that the MCP is scarce would make the AM1815 a good option (ignoring the QFN package).

joelucid

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Re: Making a lower power Moteino
« Reply #55 on: April 26, 2016, 02:12:09 AM »
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- We should also start talking about battery.

Of course you can run these from all kinds of batteries. The li-Mno2 chemistry is appealing because of all the small button cell types (cr2032, cr2450) as well as the small cylindrical shapes (cr123a or craa/2). But 2x LiFeS02 or even alkali - it all works. The Li-SOCl2 cells like the Saft are appealing if a little high-voltage because of their energy density and near constant discharge curve. Li-(CF)x (the BR coin cells) is great for long lived projects because of the low self discharge (and this actually matters once you have a 150nA sleep load!).

I think it would be nice if a coin cell or coin cell holder could directly be mounted for smaller form factor - similar to Tino or my small TH mote.

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- We should also start talking about board format, layout, pinout, perhaps battery connections depending on the battery.

I personally find that in most my motes I don't use close to all pins. So maybe doing something with a less complete pinout would be attractive in particular for the coin cell powered moteino. That said it would also be useful to have the same pinout across the board - I'm not sure what's best.

Generally I find that Motes dedicated to one purpose tend to have the better form factor in the end. So I could also see you making a TH-Mote that only exposes a hand-full of extra pins for expansion.

Quote
- We should also start talking about programmability (ISCP, FTDI) and powering it when attached to a FTDI. I am thinking it should only be able to work when its own power supply is attached (ie battery), since the 5V from FTDI will fry it (no regulator).
- the FTDI also has a 3.3v power output (via solder jumper) but it's limited to 50mA so that won't do it either.

Good points. I actually used the 3.3V FTDI output for powering modded Moteinos without regulator. I wasn't even aware of the limitation. I think it would be better to have a new FTDI connector with regulator on board than to have batteries connected while programming. Batteries won't be able to sustain the programming currents - in particular the coin cell types.

Joe

joelucid

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Re: Making a lower power Moteino
« Reply #56 on: April 27, 2016, 10:57:03 AM »
Maybe another reason for preferring a non-regulator Moteino:

As I measured bit error rates today I converted a TH Mote into something I could use by replacing the cr2032 with 2 AAA eneloop. That worked well as described in the other thread.

Now as I had this ready I also wanted to test the noise floor on it using my methodology. The results are by far the lowest numbers I have ever measured:

Apr 27 16:50:57 espgw.lx  250:1 251:3 252:5
Apr 27 16:51:14 espgw.lx  251:2 252:4 253:5
Apr 27 16:51:30 espgw.lx  250:1 251:3 252:4 253:5
Apr 27 16:51:47 espgw.lx  251:3 252:4 253:5
Apr 27 16:52:03 espgw.lx  251:5
Apr 27 16:52:19 espgw.lx  250:1 251:3 252:3 253:5
Apr 27 16:52:36 espgw.lx  250:2 251:5 252:3 253:5
Apr 27 16:52:52 espgw.lx  249:1 251:3 252:4 253:5
Apr 27 16:53:08 espgw.lx  250:1 251:3 252:5
Apr 27 16:53:25 espgw.lx  250:2 251:3 252:4 253:5
Apr 27 16:53:41 espgw.lx  251:5

This is 5khz rxbw. On this mote you could run this profile with an RSSITHRESH of 249 (-125 dBm) and still use AGC. Pretty cool. I suspect it's a benefit of not getting regulator noise. I do have a 100nF cap directly at the radio pin.

kobuki

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Re: Making a lower power Moteino
« Reply #57 on: September 07, 2016, 11:48:49 AM »
Felix, is it reasonable to expect this product this year or even in the near future? Are planned features fixed yet in any case?

Felix

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Re: Making a lower power Moteino
« Reply #58 on: September 08, 2016, 08:37:18 AM »
I will first have to be convinced by the economics if I was to "mass produce" anything like what's mentioned here :)
The [ low power + cost to make/test/own + ease of use compared to a regular Moteino ] would have to be very convincing.

kobuki

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Re: Making a lower power Moteino
« Reply #59 on: September 08, 2016, 08:45:18 AM »
OK, in my interpretation it's "not going to happen" - though I think there would be significant demand, seeing the prevalence of the myriad of battery operated nodes everywhere and the ULP operation it obviates. We'll continue to desolder the LDO then :)