Compiler error says "Function is not declared in this scope" but the function is public-CodePudding

I'm setting up an IRQ on a Raspberry Pi Pico in C but when I compile my code it tells me the callback function is "Not declared in this scope". I've been beating my head against the wall for hours because the function is declared and it's public.

#include <stdio.h>
#include "pico/stdlib.h"
#include "hardware/gpio.h"

uint64_t time_between_triggers;
uint16_t times_triggered;

void shaft_speed_init(uint8_t _gpio_number, uint8_t _precision, uint8_t _counts_per_turn){
    gpio_set_irq_enabled_with_callback(2, GPIO_IRQ_EDGE_RISE, true, &_shaft_speed_gpio_callback);

}

void _shaft_speed_gpio_callback(uint16_t _gpio, uint32_t _event_mask) {
    uint64_t trigger_time;
    static uint64_t prev_trigger_time;

    trigger_time = to_us_since_boot(get_absolute_time());
    time_between_triggers = time_between_triggers   (trigger_time - prev_trigger_time);
    prev_trigger_time = trigger_time;
    times_triggered  ;
}

[main] Building folder: variable_rate_planter 
[build] Starting build
[proc] Executing command: /usr/bin/cmake --build /home/taylor/Documents/Programs/Pi-Pico/variable_rate_planter/build --config Debug --target all --
[build] [2/8  12% :: 0.017] Performing build step for 'PioasmBuild'
[build] ninja: no work to do.
[build] [3/8  25% :: 0.026] Performing build step for 'ELF2UF2Build'
[build] ninja: no work to do.
[build] [4/8  37% :: 0.043] No install step for 'PioasmBuild'
[build] [5/8  50% :: 0.052] No install step for 'ELF2UF2Build'
[build] [6/8  62% :: 0.083] Completed 'PioasmBuild'
[build] [6/8  75% :: 0.095] Completed 'ELF2UF2Build'
[build] [7/8  87% :: 0.201] Building CXX object CMakeFiles/vrp.dir/main.cpp.obj
[build] FAILED: CMakeFiles/vrp.dir/main.cpp.obj 
[build] /usr/bin/arm-none-eabi-g   -DCFG_TUSB_DEBUG=1 -DCFG_TUSB_MCU=OPT_MCU_RP2040 -DCFG_TUSB_OS=OPT_OS_PICO -DLIB_PICO_BIT_OPS=1 -DLIB_PICO_BIT_OPS_PICO=1 -DLIB_PICO_DIVIDER=1 -DLIB_PICO_DIVIDER_HARDWARE=1 -DLIB_PICO_DOUBLE=1 -DLIB_PICO_DOUBLE_PICO=1 -DLIB_PICO_FIX_RP2040_USB_DEVICE_ENUMERATION=1 -DLIB_PICO_FLOAT=1 -DLIB_PICO_FLOAT_PICO=1 -DLIB_PICO_INT64_OPS=1 -DLIB_PICO_INT64_OPS_PICO=1 -DLIB_PICO_MALLOC=1 -DLIB_PICO_MEM_OPS=1 -DLIB_PICO_MEM_OPS_PICO=1 -DLIB_PICO_PLATFORM=1 -DLIB_PICO_PRINTF=1 -DLIB_PICO_PRINTF_PICO=1 -DLIB_PICO_RUNTIME=1 -DLIB_PICO_STANDARD_LINK=1 -DLIB_PICO_STDIO=1 -DLIB_PICO_STDIO_USB=1 -DLIB_PICO_STDLIB=1 -DLIB_PICO_SYNC=1 -DLIB_PICO_SYNC_CORE=1 -DLIB_PICO_SYNC_CRITICAL_SECTION=1 -DLIB_PICO_SYNC_MUTEX=1 -DLIB_PICO_SYNC_SEM=1 -DLIB_PICO_TIME=1 -DLIB_PICO_UNIQUE_ID=1 -DLIB_PICO_UTIL=1 -DPICO_BOARD=\"pico\" -DPICO_BUILD=1 -DPICO_CMAKE_BUILD_TYPE=\"Debug\" -DPICO_COPY_TO_RAM=0 -DPICO_CXX_ENABLE_EXCEPTIONS=0 -DPICO_NO_FLASH=0 -DPICO_NO_HARDWARE=0 -DPICO_ON_DEVICE=1 -DPICO_TARGET_NAME=\"vrp\" -DPICO_USE_BLOCKED_RAM=0 -I/home/taylor/pico/pico-sdk/src/common/pico_stdlib/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_gpio/include -I/home/taylor/pico/pico-sdk/src/common/pico_base/include -I/home/taylor/Documents/Programs/Pi-Pico/variable_rate_planter/build/generated/pico_base -I/home/taylor/pico/pico-sdk/src/boards/include -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_platform/include -I/home/taylor/pico/pico-sdk/src/rp2040/hardware_regs/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_base/include -I/home/taylor/pico/pico-sdk/src/rp2040/hardware_structs/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_claim/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_sync/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_irq/include -I/home/taylor/pico/pico-sdk/src/common/pico_sync/include -I/home/taylor/pico/pico-sdk/src/common/pico_time/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_timer/include -I/home/taylor/pico/pico-sdk/src/common/pico_util/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_uart/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_divider/include -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_runtime/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_clocks/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_resets/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_pll/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_vreg/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_watchdog/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_xosc/include -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_printf/include -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_bootrom/include -I/home/taylor/pico/pico-sdk/src/common/pico_bit_ops/include -I/home/taylor/pico/pico-sdk/src/common/pico_divider/include -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_double/include -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_int64_ops/include -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_float/include -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_malloc/include -I/home/taylor/pico/pico-sdk/src/rp2_common/boot_stage2/include -I/home/taylor/pico/pico-sdk/src/common/pico_binary_info/include -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_stdio/include -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_stdio_usb/include -I/home/taylor/pico/pico-sdk/lib/tinyusb/src -I/home/taylor/pico/pico-sdk/lib/tinyusb/src/common -I/home/taylor/pico/pico-sdk/lib/tinyusb/hw -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_fix/rp2040_usb_device_enumeration/include -I/home/taylor/pico/pico-sdk/src/rp2_common/pico_unique_id/include -I/home/taylor/pico/pico-sdk/src/rp2_common/hardware_flash/include -I/home/taylor/pico/pico-sdk/src/common/pico_usb_reset_interface/include -mcpu=cortex-m0plus -mthumb -Og -g -ffunction-sections -fdata-sections -fno-exceptions -fno-unwind-tables -fno-rtti -fno-use-cxa-atexit -MD -MT CMakeFiles/vrp.dir/main.cpp.obj -MF CMakeFiles/vrp.dir/main.cpp.obj.d -o CMakeFiles/vrp.dir/main.cpp.obj -c /home/taylor/Documents/Programs/Pi-Pico/variable_rate_planter/main.cpp
[build] In file included from /home/taylor/Documents/Programs/Pi-Pico/variable_rate_planter/main.cpp:4:
[build] /home/taylor/Documents/Programs/Pi-Pico/variable_rate_planter/shaft_speed.h: In function 'void shaft_speed_init(uint8_t, uint8_t, uint8_t)':
[build] /home/taylor/Documents/Programs/Pi-Pico/variable_rate_planter/shaft_speed.h:9:70: error: '_shaft_speed_gpio_callback' was not declared in this scope
[build]     9 |     gpio_set_irq_enabled_with_callback(2, GPIO_IRQ_EDGE_RISE, true, &_shaft_speed_gpio_callback);
[build]       |                                                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~
[build] ninja: build stopped: subcommand failed.
[proc] The command: /usr/bin/cmake --build /home/taylor/Documents/Programs/Pi-Pico/variable_rate_planter/build --config Debug --target all -- exited with code: 1 and signal: null
[build] Build finished with exit code 1

CodePudding user response：

Your function _shaft_speed_gpio_callback appears to be defined after the point in the code where it's used. You need to add a function declaration (a.k.a "prototype") so the compiler knows what the name refers to:

// Add this
void _shaft_speed_gpio_callback(uint16_t _gpio, uint32_t _event_mask);

// The rest of your code as provided
void shaft_speed_init(uint8_t _gpio_number, uint8_t _precision, uint8_t _counts_per_turn){
    gpio_set_irq_enabled_with_callback(2, GPIO_IRQ_EDGE_RISE, true, &_shaft_speed_gpio_callback);
}

void _shaft_speed_gpio_callback(uint16_t _gpio, uint32_t _event_mask) {
    // ...
}