# Low memory available?
**URL:** https://community.keyboard.io/t/low-memory-available/430
**Category:** Programming
**Created:** [October 16, 2017, 9:52pm UTC](https://community.keyboard.io/t/low-memory-available/430 "2017-10-16T21:52:45Z")
**Posts on this page:** 13
**Page:** 1
### Author:  [@james.nvc](https://community.keyboard.io/u/james.nvc)
#### Post date: [October 16, 2017, 9:52pm UTC](https://community.keyboard.io/t/low-memory-available/430/1 "2017-10-16T21:52:45Z")
I’m theorycrafting my keyboard layout at the moment and arduino IDE is giving me a scary warning about low dynamic memory that may cause stability problems when compiling/verifying.
```auto
Sketch uses 21,512 bytes (75%) of program storage space. Maximum is 28,672 bytes.
Global variables use 2,046 bytes (79%) of dynamic memory, leaving 514 bytes for local variables. Maximum is 2,560 bytes.
Low memory available, stability problems may occur.
```
I don’t have a unit to test on yet, so I’m not sure if these stability problems are something I need to worry about, but is this something to be concerned about? Am I doing something strange/incorrect to cause 2k of global variables?
Source for layout is [here](https://bitbucket.org/jamesnvc/keyboardiolayout/src).
---
### Author:  [@jesse](https://community.keyboard.io/u/jesse)
#### Post date: [October 16, 2017, 10:21pm UTC](https://community.keyboard.io/t/low-memory-available/430/2 "2017-10-16T22:21:47Z")
It’s hard for me to be sure without testing. There’s definitely optimization to be done.
---
### Author:  [@algernon](https://community.keyboard.io/u/algernon)
#### Post date: [October 16, 2017, 10:30pm UTC](https://community.keyboard.io/t/low-memory-available/430/3 "2017-10-16T22:30:06Z")
That’s quite a bit of memory used! For reference, I’m at 1905 bytes, 74.4%, probably 0.6% below the warning threshold. I’ll have a look at your sketch to see what’s eating your memory.
---
### Author:  [@algernon](https://community.keyboard.io/u/algernon)
#### Post date: [October 16, 2017, 10:38pm UTC](https://community.keyboard.io/t/low-memory-available/430/4 "2017-10-16T22:38:40Z")
Interesting! Compiling the sketch here on Linux, Arduino 1.8.0 (with avr-gcc 4.9.2) yields:
```nohighlight
- Size: firmware/james_layout/james_layout-0.0.0-gb0eb-dirty.elf
- Program: 20886 bytes (72.8% Full)
- Data: 1782 bytes (69.6% Full)
```
1.7k is perfectly reasonable, and I don’t see anything in the sketch that would increase memory use so drastically. What OS are you on, and what version of Arduino (& gcc/clang) are you using with it?
---
### Author:  [@james.nvc](https://community.keyboard.io/u/james.nvc)
#### Post date: [October 16, 2017, 10:50pm UTC](https://community.keyboard.io/t/low-memory-available/430/5 "2017-10-16T22:50:24Z")
Ah! Apparently I was using Arduino 1.6.13 instead of 1.8.3. I switched to 1.8.3 & I’m down to 69%. My mistake!
For future reference though (as I think I’m probably going to start hitting that warning again soon), are there patterns one should be following/avoiding to keep memory usage reasonable?
---
### Author:  [@algernon](https://community.keyboard.io/u/algernon)
#### Post date: [October 16, 2017, 10:57pm UTC](https://community.keyboard.io/t/low-memory-available/430/6 "2017-10-16T22:57:05Z")
> [@james.nvc](#):
>
> For future reference though (as I think I’m probably going to start hitting that warning again soon), are there patterns one should be following/avoiding to keep memory usage reasonable?
Most of the time when I noticed an increase in memory use, was because I started using structures that were just too big.
Whenever you need to store something in a global, try to find a way to store as little as possible, or push the data to `PROGMEM` or `EEPROM`. Only keep in RAM what absolutely must be read-writeable at run-time. And don’t use things like `bool stateMap[8]` when you could use `uint8_t stateMap` and bit operations (and save 7 bytes!).
---
### Author:  [@james.nvc](https://community.keyboard.io/u/james.nvc)
#### Post date: [October 16, 2017, 11:03pm UTC](https://community.keyboard.io/t/low-memory-available/430/7 "2017-10-16T23:03:30Z")
> [@algernon](#):
>
> push the data to PROGMEM or EEPROM
For `PROGMEM`, if I understand the [Arduino documentation](https://www.arduino.cc/en/Reference/PROGMEM), that means I just declare the variable with `PROGMEM`?
For storing in EEPROM, that means using the EEPROM `get`/`set` functions?
Thanks so much for your help!
---
### Author:  [@algernon](https://community.keyboard.io/u/algernon)
#### Post date: [October 16, 2017, 11:08pm UTC](https://community.keyboard.io/t/low-memory-available/430/8 "2017-10-16T23:08:07Z")
> [@james.nvc](#):
>
> For PROGMEM, if I understand the Arduino documentation, that means I just declare the variable with PROGMEM?
Almost. You’ll need to use the `pgm_read_byte`/`pgm_read_word`-family of functions to read data back from there, too.
> [@james.nvc](#):
>
> For storing in EEPROM, that means using the EEPROM get/set functions?
Yes. Perhaps in combination with the [EEPROM-Settings](https://github.com/keyboardio/Kaleidoscope-EEPROM-Settings) plugin, if you want to be able to use other plugins that use EEPROM for settings.
---
### Author:  [@james.nvc](https://community.keyboard.io/u/james.nvc)
#### Post date: [October 16, 2017, 11:29pm UTC](https://community.keyboard.io/t/low-memory-available/430/9 "2017-10-16T23:29:13Z")
Hm…I’m a bit confused now. I added a bit more to [my sketch](https://bitbucket.org/jamesnvc/keyboardiolayout/src/8186e0f49a05c073bad1e4f2f3f6da1bf9b6d99c/james_layout.ino?at=master&fileviewer=file-view-default) and I’m back to 79% and getting the warning.
However, I’m not clear exactly what’s consuming memory for me: Looking at my sketch, as far as I can tell, it’s just function definitions, enums, and PROGMEM structures. I have some LED structs declared, but removing those only drops usage down 1%.
I think I’m missing something…
---
### Author:  [@james.nvc](https://community.keyboard.io/u/james.nvc)
#### Post date: [October 16, 2017, 11:40pm UTC](https://community.keyboard.io/t/low-memory-available/430/10 "2017-10-16T23:40:41Z")
Ah, I think I was missing the obvious - I’m including a bunch of plugins that themselves use SRAM. I think I can remove a few LED effects and get back under the threshold.
---
### Author:  [@algernon](https://community.keyboard.io/u/algernon)
#### Post date: [October 16, 2017, 11:42pm UTC](https://community.keyboard.io/t/low-memory-available/430/11 "2017-10-16T23:42:08Z")
The biggest one there is `HostOS`, with its OS-guesser mode enabled. That pulls in the `FingerprintUSBHost` library which uses a lot of RAM, well over 250 bytes. Looking at its code, I think we could reduce that significantly… until then, `#define KALEIDOSCOPE_HOSTOS_GUESSER 0` will help, at the cost of not guessing the OS at boot time.
> [@james.nvc](#):
>
> Ah, I think I was missing the obvious - I’m including a bunch of plugins that themselves use SRAM.
Yep! Plugins will add some RAM usage, some more than others. LED effects usually use little SRAM, surprisingly.
---
### Author:  [@james.nvc](https://community.keyboard.io/u/james.nvc)
#### Post date: [October 16, 2017, 11:44pm UTC](https://community.keyboard.io/t/low-memory-available/430/12 "2017-10-16T23:44:43Z")
> [@algernon](#):
>
> The biggest one there is HostOS, with its OS-guesser mode enabled
Ah, that would explain it!
> [@algernon](#):
>
> LED effects usually use little SRAM
The first one I looked at was the Stalker effect, which declares a 2D array & was 4% of my RAM – I guess that’s not representative 😛
Thanks again for your assistance, I really appreciate it!
---
### Author:  [@algernon](https://community.keyboard.io/u/algernon)
#### Post date: [October 16, 2017, 11:45pm UTC](https://community.keyboard.io/t/low-memory-available/430/13 "2017-10-16T23:45:41Z")
> [@james.nvc](#):
>
> The first one I looked at was the Stalker effect, which declares a 2D array & was 4% of my RAM – I guess that’s not representative 😛
Stalker is one of the outliers =)