mirrors/qmk_firmware
1
0
Fork 1
mirror of https://github.com/qmk/qmk_firmware synced 2024-11-18 01:46:09 +00:00
Code Issues Projects Releases Packages Wiki Activity

[Core] Allow usage of AVRs minimal printf library (#16266)

Browse source 
Co-authored-by: Sergey Vlasov <sigprof@gmail.com>
This commit is contained in:
Stefan Kerkmann 2022-04-22 10:13:31 +02:00 committed by GitHub
parent 68a3fe8347
commit b1681fb6a1
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
2 changed files with 22 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
docs/squeezing_avr.md
View file

@ -30,6 +30,19 @@ MAGIC_ENABLE = no
These features are enabled by default, but may not be needed. Double check to make sure, though.
Largest in size is "magic" -- the QMK magic keycodes -- which control things like NKRO toggling, GUI and ALT/CTRL swapping, etc. Disabling it will disable those functions.
If you use `sprintf` or `snprintf` functions you can save around ~400 Bytes by enabling this option.
```make
AVR_USE_MINIMAL_PRINTF = yes
```
This will include smaller implementations from AVRs libc into your Firmware. They are [not fully featured](https://www.nongnu.org/avr-libc/user-manual/group__avr__stdio.html#gaa3b98c0d17b35642c0f3e4649092b9f1), for instance zero padding and field width specifiers are not supported. So if you use `sprintf` or `snprintf` like this:
```c
sprintf(wpm_str, "%03d", get_current_wpm());
snprintf(keylog_str, sizeof(keylog_str), "%dx%d, k%2d : %c");
```
you will still need the standard implementation.
## `config.h` Settings
If you've done all of that, and you don't want to disable features like RGB, Audio, OLEDs, etc, there are some additional options that you can add to your config.h that can help.

9
platforms/avr/platform.mk
View file

@ -37,6 +37,15 @@ CXXFLAGS += -fno-exceptions -std=c++11
LDFLAGS += -Wl,--gc-sections
# Use AVR's libc minimal printf implementation which has less features
# and thus can shave ~400 bytes. Usually we use the xprintf
# implementation but keyboards that use s(n)printf automatically
# pull in the AVR libc implementation, which is ~900 bytes heavy.
AVR_USE_MINIMAL_PRINTF ?= no
ifeq ($(strip $(AVR_USE_MINIMAL_PRINTF)), yes)
LDFLAGS += -Wl,--whole-archive -lprintf_min -Wl,--no-whole-archive
endif
OPT_DEFS += -DF_CPU=$(F_CPU)UL
MCUFLAGS = -mmcu=$(MCU)