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FONE with two Feathers?
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

FONE with two Feathers?

by fgnievinski on Tue Jan 26, 2021 9:12 pm

Greetings.

Currently I use the following parts:

A1) Adafruit Feather M0 Adalogger
https://www.adafruit.com/product/2796

A2) Adafruit Ultimate GPS FeatherWing
https://www.adafruit.com/product/3133

Now I'd like to add a FONA.

Ideally there would be a FONA featherwing.
But the only option is a full FONA feather:

A3) Adafruit Feather 32u4 FONA
https://www.adafruit.com/product/3027

- My question is: will two Feathers
play well stacked together?
Can I use one as a wing?

I'd like to keep using the M0
because 32u4 is too limited.
Otherwise, I'd probably choose
set B below instead of set A above:

B1) Adafruit Feather 32u4 FONA
https://www.adafruit.com/product/3027
B2) Adafruit Ultimate GPS FeatherWing
https://www.adafruit.com/product/3133
B3) Adalogger FeatherWing - RTC + SD Add-on
https://www.adafruit.com/product/2922

Thanks for your help!
-Felipe.

fgnievinski
 
Posts: 31
Joined: Wed Sep 09, 2015 10:42 am

Re: FONE with two Feathers?

by adafruit_support_mike on Thu Jan 28, 2021 12:37 am

Stacking Feathers doesn't work. Each one wants to control the IO pins, so they'll fight in ways that could damage either or both boards.

You can create a Serial connection between a FONA Feather 32u4 and a Feather M0 though. The 32u4 uses pins 8 and 9 to talk to the SIM800 module, and those are independed of the pins connected to TX/RX at the side of the board. Both Feathers also handle USB internally, so the Serial interface that talks to a computer only exists in code. Both sets of TX/RX pins are free for other uses, and are identified as interface Serial1 in code.

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Re: FONE with two Feathers?

by fgnievinski on Thu Jan 28, 2021 12:14 pm

Thank you for clarifying that Feathers are not supposed
to be stacked -- max is 1 Feather + multiple Featherwings.

Now I wonder if I should use this larger board instead?

Adafruit FONA - Mini Cellular GSM Breakout uFL Version
https://www.adafruit.com/product/1946

I'm also a little concerned with the power supply.
Can I route energy from one Feather to another?
I'm hoping not having to duplicate the power supply system.
I'm using a solar panel and battery with this charger:

USB / DC / Solar Lithium Ion/Polymer charger - v2
https://www.adafruit.com/product/390

Thank you!
-Felipe.

fgnievinski
 
Posts: 31
Joined: Wed Sep 09, 2015 10:42 am

Re: FONE with two Feathers?

by adafruit_support_mike on Thu Jan 28, 2021 11:24 pm

fgnievinski wrote:Now I wonder if I should use this larger board instead?

You can, but it probably isn't necessary. You'll have to deal with the same communication issues among the microcontrollers and the FONA either way.

fgnievinski wrote:I'm also a little concerned with the power supply. Can I route energy from one Feather to another?

You can power multiple microcontrollers from the same power supply, that's no problem.

The only point where you'll need to be careful involves the FONA: when the radio is active, it can use bursts of current up to 2A. Make sure you have a direct, low-resistance connection between the power supply and the FONA, and make sure the power supply can handle the peak load.

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Posts: 63052
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Re: FONE with two Feathers?

by fgnievinski on Fri Feb 05, 2021 3:51 pm

Hi, thanks again for your support.

I'm still trying to adapt my current power supply system:

- USB / DC / Solar Lithium Ion/Polymer charger - v2
https://www.adafruit.com/product/390

- Lithium Ion Battery Pack - 3.7V 4400mAh
https://www.adafruit.com/product/354

- Large 6V 3.5W Solar panel - 3.5 Watt
https://www.adafruit.com/product/500

It's being used for an outdoor station based on this board:

- Feather 32u4 Adalogger
https://www.adafruit.com/product/2795

From the Feather 32u4 FONA's tutorial, I garner "You must have a Lipoly/LiIon battery plugged in at all times for using the Feather FONA", to accommodate the high intensity short lived peaks (2A for a few ms).

https://learn.adafruit.com/adafruit-fea ... -1753146-2

So the easiest thing would be to have a second battery just for the FONA. The first problem that I ran into was how to feed FONA's built-in charger. The tutorial discouraged to "Connect an external 5V power supply to the USB and GND pins", recommending to "wire it to a USB cable's 5V and GND input".

https://learn.adafruit.com/adafruit-fea ... 3016720-12

Apart from the need for a USB cable plug, I'm not sure FONA's internal regulator would be okay with the chager's output voltage range? The solar charger tutorial says "LOAD output can be as high as 6VDC if in direct sun because it will draw current directly from the 6V panel instead of from the battery." But the LOAD output can also be as low as 3.1V when on batteries (overnight). I also assume the solar charger's LOAD output can be shared in parallel between the two Feathers?

https://learn.adafruit.com/usb-dc-and-s ... 1887758-11

Another option would be the following:
- keep a single battery plugged in to the FONA
- plug the solar charger's LOAD output only to the FONA (via USB?)
- plug Adalogger's BAT pin to FONA's 3.3V regulator output.

Would there be a third, easier alternative for powering both the 32u4 and FONA, please?

Thanks,
-FGN.

fgnievinski
 
Posts: 31
Joined: Wed Sep 09, 2015 10:42 am

Please be positive and constructive with your questions and comments.