LowPowerLab Forum

Hardware support => RF - Range - Antennas - RFM69 library => Topic started by: ColinR on January 01, 2015, 03:36:45 PM

Title: RFM69 teensy?
Post by: ColinR on January 01, 2015, 03:36:45 PM
Anybody used RFM69 with a teensy? I have one collecting dust and am trying to figure out what I want to do with it. Obviously I want to use some RF.

Title: Re: RFM69 teensy?
Post by: Felix on January 01, 2015, 05:58:51 PM
I have a teensy collecting dust as well. For about 3 years.
It's not the right size so I can't really use it for anything, I keep it for price-comparison pictures :)
Title: Re: RFM69 teensy?
Post by: ColinR on January 02, 2015, 01:39:42 AM

So I guess the thing would be to use the Teensy for what it can do and the Atmega can't. It has an analog output, it's faster and has shit-tons of memory. I could use the AOUT with a MOSFET to dim something, I suppose. Hmm. Maybe with a photodiode light input? Dim a light based on ambient light ... let me think about where this could be useful.
Title: Re: RFM69 teensy?
Post by: ColinR on January 02, 2015, 03:34:20 AM
You have to be impressed, however, at the form factor of the thing. On-board FTDI and a killer processor in a footprint smaller than an R4, way smaller than a MEGA, and with some serious firepower. No RF, of course, but pretty impressive nonetheless.

The footprint was not a big issue until this recent project (the thermostat) where I wanted a MEGA but my real estate was seriously limited. I ended up with a doubledecker PCB, which was useful for other reasons in the end (getting the LCD and bar display near the top of the enclosure), but smaller is (as you know) always better!

Title: Re: RFM69 teensy?
Post by: Felix on January 02, 2015, 08:24:43 AM
I do agree the features are great. Back when i started designing Moteino I made it as small as possible, it was probably very similar in size to teensy. That was the very first ever prototype revision made at OSHPark. Until I got them and realized how dumb I was for not even doing a fitting test for the RFM radios. While the footprint of the RFM12B would fit on the back, when I needed to solder the headers I could not because the PCB of RFM12B would cover the side header pins. Fail... So I had to enlarge it to the next 0.1" multiple width, to keep it breadboard friendly and fit the radios and be able to solder headers. So there's the size story. In my practice I designed an atmega328 PCB that was 10mm in diameter and used the QFN28 atmega328 and 0402 passives. Yes, that small, so it can be done, it's just a matter of whether it is practical or not. The current Moteino format is what covers close to 99% of cases. The MEGA is that big because all the headers needed to be broken out. Custom versions can always be made where all the pins are not needed and real-estate is crucial. I believe the MEGA is close to teensy in memory, but no analog output and the bootloader is not a USB one but a traditional custom arduino bootloader. I went with the atmegas because it's the easiest thing for people to get started with and most familiar when it comes to the Arduino world.
Title: Re: RFM69 teensy?
Post by: ColinR on January 03, 2015, 02:10:49 AM
Hey, don't get me wrong. I wasn't second-guessing anything you've done. I think you made all the right decisions. I followed your explanation and agreed each step of the way.

Very solid point about breaking out all of the pins. A Moteino works for 100% of use cases with pins. A huge plus. I just ran into a use-case where my four IO on my remote node was just not enough, so I'll have to make an extended remote board to have at least 8 IO.