Hi,
I have a project where I use an Adafruit Feather 32u4 to emulate a keyboard via USB and Bluetooth. Everything works but I have run out of program space and I still need to implement some data logging on an SD card.
Would it be feasible to use a second controller, e.g. a Pro Mini to handle the data logging and then communicate with it via I2C? The Mini needs to be powered from the Feather, but as far as I know that should not be a problem?
SomethingClever:
The Mini needs to be powered from the Feather, but as far as I know that should not be a problem?
The Mini power input is 7-9V. How are you connecting it to the Feather to get a voltage in that range?
SomethingClever:
Would it be feasible to use a second controller, e.g. a Pro Mini to handle the data logging and then communicate with it via I2C?
Sure why not? There's an example around here on connecting to Arduinos via I2C.
SomethingClever:
Hi,I have a project where I use an Adafruit Feather 32u4 to emulate a keyboard via USB and Bluetooth. Everything works but I have run out of program space and I still need to implement some data logging on an SD card.
Would it be feasible to use a second controller, e.g. a Pro Mini to handle the data logging and then communicate with it via I2C? The Mini needs to be powered from the Feather, but as far as I know that should not be a problem?
Personally I think it would be more feasible to use their data logging feather if you have the available pins. Merely just a suggestion. I have a couple of feathers myself and love that they all layer with ease.
Blade2021:
Personally I think it would be more feasible to use their data logging feather if you have the available pins. Merely just a suggestion. I have a couple of feathers myself and love that they all layer with ease.
Would a datalog feather provide additional memory over the Adafruit Feather 32u4 that is already full?
adwsystems:
The Mini power input is 7-9V. How are you connecting it to the Feather to get a voltage in that range?
Nonsense. I'm powering mine always from USB (5V) and there are 3.3V versions around as well. No need to supply that high a voltage - unless you like to stress its tiny built-in regulator of course.
wvmarle:
Nonsense. I'm powering mine always from USB (5V) and there are 3.3V versions around as well. No need to supply that high a voltage - unless you like to stress its tiny built-in regulator of course.
Hey man, don't shoot the messenger. I'm just referencing the product list https://www.arduino.cc/en/Products/Compare
adwsystems:
The Mini power input is 7-9V. How are you connecting it to the Feather to get a voltage in that range?Sure why not? There's an example around here on connecting to Arduinos via I2C.
It says here that the input power is 3.35-12v, so I guess the Feather's 3.3v is not enough. I thought a 3.3v system could power another 3.3v system. Do you know if it will work if I step up the voltage?
Blade2021:
Personally I think it would be more feasible to use their data logging feather if you have the available pins. Merely just a suggestion. I have a couple of feathers myself and love that they all layer with ease.
As adwsystems says, I don't think it will change my program space, as I still need the same libraries as now.
SomethingClever:
It says here that the input power is 3.35-12v.
My bad. I missed the 'Pro' in Pro Mini.
What is powering the Feather? Why not split the incoming power?
Pro Mini (which OP said they have) is listed as 5-12V input for the 5V versions (like I use myself).
The Mini (those designations get more and more confusing) is indeed a bit different again, but does have 5V pins.
SomethingClever:
It says here that the input power is 3.35-12v, so I guess the Feather's 3.3v is not enough.
I noticed that; it's indeed outright weird. I don't know why they ask for that extra 0.05V - nor do I believe it will make a difference. You can of course just connect it to the same power supply you use for the Feather, instead of taxing the Feather's built-in regulator.
The main problem is the overall power supply. An SD card can draw quite some power when active, and that's not what those little regulators can handle.
adwsystems:
My bad. I missed the 'Pro' in Pro Mini.What is powering the Feather? Why not split the incoming power?
The Feather is powered by USB and by a 3.7v Lipo battery when not plugged in. It has a built in battery charger so I don't have to worry about that.
I guess I could power the Pro Mini with the battery.
wvmarle:
The main problem is the overall power supply. An SD card can draw quite some power when active, and that's not what those little regulators can handle.
The Pro Mini will only have the SD card reader attached and nothing else that draws power. Shouldn't it be able to handle that?
SomethingClever:
Hi,I have a project where I use an Adafruit Feather 32u4 to emulate a keyboard via USB and Bluetooth. Everything works but I have run out of program space .....
maybe just post your code and see if any of the Guru's here can offer suggestions to reduce your program to a smaller footprint ?
SomethingClever:
The Feather is powered by USB and by a 3.7v Lipo battery when not plugged in. It has a built in battery charger so I don't have to worry about that.
Both power supplies are fine for a Pro Mini. It's got it's on-board regulator so will step down the voltage to the correct level.
The Pro Mini will only have the SD card reader attached and nothing else that draws power. Shouldn't it be able to handle that?
Probably can - it's the regulator that's the limiting factor.
dave-in-nj:
maybe just post your code and see if any of the Guru's here can offer suggestions to reduce your program to a smaller footprint ?
Not a Guru but always in for a challenge like that 
I have found some of the adafruit libraries bloated
and with my sloppy programming, I tend to write out things in loooong hand to is it easier for me to follow,
dave-in-nj:
and with my sloppy programming,I tend to write out things in loooong hand to is it easier for me to follow,
I write things out long hand as a rule. The rule being to not program anything in a way I will have to reverse engineer or re-figure out two months from now.
dave-in-nj:
maybe just post your code and see if any of the Guru's here can offer suggestions to reduce your program to a smaller footprint ?
for the SD library? it would have to be a lot of strings without F macro and constant arrays without PROGMEM. The SD library takes 500 bytes for cache.
If it is working, then your proved that it works !
you should be able to get a second device that uses the same voltage and that way to share one power supply.
the options are many.
get a larger single CPU and replace the feather and do it all with one. ESP32 ?
get a smaller board that uses the same voltage as your feather, use one power supply, but split
I have a WEMOS-D1 with a SD card shield in my stock... not used yet.
the D1 does not have a lot of pins, only 1 analog pin.
but the fact it can have the shield added makes it very convenient.
I skimmed your code, lots of repetition, not a lot of memory for the code. I ASSUME the bulk is the libraries.
I wanted to compile your code with just libraries and then again with just the code to see the memory use for each part... alas, mid-week is not my free time.
if all you need at this moment is a working prototype, you seem to have it.
since you got an Arduino to work, you can get it to work in any of the other forms. UNO/NANO/MINI....
if you need a 100% completed project... you waited to the last minute. you must be a student or an American....
Thanks for the reply!
A 32u4 board fits the project really well as it has the USB transceiver, and as the Feather has both BlueTooth LE and built in battery charger it seemed like a good choice when the need is to emulate a keyboard on both USB and BT.
For the power, I think I will power the other board, probably a Pro Mini, from the battery so it will also work when the prototype does not receive USB power. Do you think that will be a problem?
I also think the bulk is libraries, but the switch cases do take up a lot of space - as far as I can calculate around 5% each, amounting to 25% of total program space.
All I need at this moment is a working prototype that can be used for a couple of weeks. I really could not have come much further by now, as our thesis is much more about the development process than the prototype itself. There have been a lot of complexity added along the way that we could not have foreseen.
I am not American, but I am a student, and this project is for my thesis