`shiftIn` + `shiftOut` not implemented

[per1234]

Describe the bug

The shiftIn and shiftOut functions are part of the standardized Arduino core API:

It is expected that every core will implement these functions.

🐛 These functions have not been implemented in this core, which causes compilation of any sketch program referencing them to fail.

Target board + cli verbose compilation output

FQBN: arduino-dev:zephyr:unoq
Using board 'unoq' from platform in folder: /home/per/Arduino/hardware/arduino-dev/zephyr
Using core 'arduino' from platform in folder: /home/per/Arduino/hardware/arduino-dev/zephyr

Detecting libraries used...
/home/per/.arduino15/packages/zephyr/tools/arm-zephyr-eabi/0.16.8/bin/arm-zephyr-eabi-g++ -g -Os -std=gnu++17 -c -D_PICOLIBC_CTYPE_SMALL=1 -w -imacros/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/llext-edk/include/zephyr/include/generated/zephyr/autoconf.h -imacros/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/llext-edk/include/zephyr/include/zephyr/toolchain/zephyr_stdint.h @/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/cxxflags.txt -fno-exceptions -fno-rtti -fno-threadsafe-statics -fno-unwind-tables -fno-use-cxa-atexit -lstdc++ -lsupc++ -lnosys -nostdlib -lstdc++ -lsupc++ -lm -fno-exceptions -fno-rtti -fdata-sections -ffunction-sections -fno-unwind-tables -mcpu=cortex-m33 -mfloat-abi=hard -mfpu=fpv5-sp-d16 -w -x c++ -E -CC -DARDUINO=10607 -DARDUINO_UNO_Q -DARDUINO_ARCH_ZEPHYR -DARDUINO_ARCH_ZEPHYR -DARDUINO_LIBRARY_DISCOVERY_PHASE=1 -I/home/per/Arduino/hardware/arduino-dev/zephyr/cores/arduino -I/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx -I/home/per/Arduino/hardware/arduino-dev/zephyr/cores/arduino/api/deprecated -I/home/per/Arduino/hardware/arduino-dev/zephyr/cores/arduino/api/deprecated-avr-comp -iprefix/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx @/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/includes.txt /home/per/.cache/arduino/sketches/C2E1E84F507BEC59F3E0FE043B27681B/sketch/sketch_feb16a.ino.cpp -o /dev/null
Generating function prototypes...
/home/per/.arduino15/packages/zephyr/tools/arm-zephyr-eabi/0.16.8/bin/arm-zephyr-eabi-g++ -g -Os -std=gnu++17 -c -D_PICOLIBC_CTYPE_SMALL=1 -w -imacros/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/llext-edk/include/zephyr/include/generated/zephyr/autoconf.h -imacros/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/llext-edk/include/zephyr/include/zephyr/toolchain/zephyr_stdint.h @/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/cxxflags.txt -fno-exceptions -fno-rtti -fno-threadsafe-statics -fno-unwind-tables -fno-use-cxa-atexit -lstdc++ -lsupc++ -lnosys -nostdlib -lstdc++ -lsupc++ -lm -fno-exceptions -fno-rtti -fdata-sections -ffunction-sections -fno-unwind-tables -mcpu=cortex-m33 -mfloat-abi=hard -mfpu=fpv5-sp-d16 -w -x c++ -E -CC -DARDUINO=10607 -DARDUINO_UNO_Q -DARDUINO_ARCH_ZEPHYR -DARDUINO_ARCH_ZEPHYR -DARDUINO_LIBRARY_DISCOVERY_PHASE=1 -I/home/per/Arduino/hardware/arduino-dev/zephyr/cores/arduino -I/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx -I/home/per/Arduino/hardware/arduino-dev/zephyr/cores/arduino/api/deprecated -I/home/per/Arduino/hardware/arduino-dev/zephyr/cores/arduino/api/deprecated-avr-comp -iprefix/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx @/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/includes.txt /home/per/.cache/arduino/sketches/C2E1E84F507BEC59F3E0FE043B27681B/sketch/sketch_feb16a.ino.cpp -o /tmp/3377184631/sketch_merged.cpp
/home/per/.arduino15/packages/builtin/tools/ctags/5.8-arduino11/ctags -u --language-force=c++ -f - --c++-kinds=svpf --fields=KSTtzns --line-directives /tmp/3377184631/sketch_merged.cpp

Compiling sketch...
/home/per/.arduino15/packages/zephyr/tools/arm-zephyr-eabi/0.16.8/bin/arm-zephyr-eabi-g++ -g -Os -std=gnu++17 -c -D_PICOLIBC_CTYPE_SMALL=1 -w -imacros/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/llext-edk/include/zephyr/include/generated/zephyr/autoconf.h -imacros/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/llext-edk/include/zephyr/include/zephyr/toolchain/zephyr_stdint.h @/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/cxxflags.txt -fno-exceptions -fno-rtti -fno-threadsafe-statics -fno-unwind-tables -fno-use-cxa-atexit -lstdc++ -lsupc++ -lnosys -nostdlib -lstdc++ -lsupc++ -lm -fno-exceptions -fno-rtti -fdata-sections -ffunction-sections -fno-unwind-tables -MMD -mcpu=cortex-m33 -mfloat-abi=hard -mfpu=fpv5-sp-d16 -DARDUINO=10607 -DARDUINO_UNO_Q -DARDUINO_ARCH_ZEPHYR -DARDUINO_ARCH_ZEPHYR -DARDUINO_LIBRARY_DISCOVERY_PHASE=0 -I/home/per/Arduino/hardware/arduino-dev/zephyr/cores/arduino -I/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx -I/home/per/Arduino/hardware/arduino-dev/zephyr/cores/arduino/api/deprecated -I/home/per/Arduino/hardware/arduino-dev/zephyr/cores/arduino/api/deprecated-avr-comp -iprefix/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx @/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/includes.txt /home/per/.cache/arduino/sketches/C2E1E84F507BEC59F3E0FE043B27681B/sketch/sketch_feb16a.ino.cpp -o /home/per/.cache/arduino/sketches/C2E1E84F507BEC59F3E0FE043B27681B/sketch/sketch_feb16a.ino.cpp.o
Compiling libraries...
Compiling core...
Using previously compiled file: /home/per/.cache/arduino/sketches/C2E1E84F507BEC59F3E0FE043B27681B/core/analogReference.cpp.o
Using precompiled core: /home/per/.cache/arduino/cores/cd06985031a4388a327205bbbe5be235/core.a
/home/per/.arduino15/packages/zephyr/tools/arm-zephyr-eabi/0.16.8/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld: Linking everything together...
/home/per/.arduino15/packages/zephyr/tools/arm-zephyr-eabi/0.16.8/bin/arm-zephyr-eabi-g++ -L/home/per/.cache/arduino/sketches/C2E1E84F507BEC59F3E0FE043B27681B -L/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx -Wl,--gc-sections -mcpu=cortex-m33 -mfloat-abi=hard -mfpu=fpv5-sp-d16 -std=gnu++17 -fno-exceptions -fno-rtti -fno-threadsafe-statics -fno-unwind-tables -fno-use-cxa-atexit -lstdc++ -lsupc++ -lnosys -nostdlib --specs=nano.specs --specs=nosys.specs /home/per/.cache/arduino/sketches/C2E1E84F507BEC59F3E0FE043B27681B/sketch/sketch_feb16a.ino.cpp.o /home/per/.cache/arduino/sketches/C2E1E84F507BEC59F3E0FE043B27681B/core/analogReference.cpp.o -Wl,--start-group /home/per/.cache/arduino/sketches/C2E1E84F507BEC59F3E0FE043B27681B/../../cores/cd06985031a4388a327205bbbe5be235/core.a -lstdc++ -lsupc++ -lm -Wl,--end-group -e main -T/home/per/Arduino/hardware/arduino-dev/zephyr/variants/arduino_uno_q_stm32u585xx/syms-dynamic.ld -T/home/per/Arduino/hardware/arduino-dev/zephyr/variants/_ldscripts/memory-check.ld -T/home/per/Arduino/hardware/arduino-dev/zephyr/variants/_ldscripts/build-static.ld -o /home/per/.cache/arduino/sketches/C2E1E84F507BEC59F3E0FE043B27681B/sketch_feb16a.ino_check.tmp
/home/per/.cache/arduino/sketches/C2E1E84F507BEC59F3E0FE043B27681B/sketch/sketch_feb16a.ino.cpp.o: in function `setup':
/tmp/.arduinoIDE-unsaved2026116-88512-1ow9ssf.xfr/sketch_feb16a/sketch_feb16a.ino:3: undefined reference to `shiftOut'
/home/per/.arduino15/packages/zephyr/tools/arm-zephyr-eabi/0.16.8/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld: /tmp/.arduinoIDE-unsaved2026116-88512-1ow9ssf.xfr/sketch_feb16a/sketch_feb16a.ino:3: undefined reference to `shiftIn'
collect2: error: ld returned 1 exit status
exit status 1

Compilation error: exit status 1

Mandatory: attach the sketch

void setup() {
  shiftIn(2, 3, MSBFIRST);
  shiftOut(4, 5, LSBFIRST, 42);
}
void loop() {}

Additional context

Reproduced using 87421b4

---

Originally reported at https://forum.arduino.cc/t/74hc595-with-arduino-uno-q/1424622