ESP32 Forum

Posted: **Fri Mar 30, 2018 10:23 am**

Hi,

I'm using an ESP32 and a sensor which is connected via I2C. For a better code structure, I wrote a component "mySensor" which handles the I2C stuff and implements the logic. Some methods are

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initialize_i2c

and

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start_reading

.

The project structure looks like this:
-Project
--components
---mySensor
----mySensor.c
----mySensor.h
----component.mk
--main
---main.c
---component.mk

In main.c I included the component with

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#include "../components/mySensor/mySensor.h"

and in app_main I call

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initialize_i2c

After 'make flash' I get this error:

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LD build/sensorboard.elf
C:/workspace/Project/build/main\libmain.a(main.o):(.literal.app_main+0x28): undefined reference to `initialize_i2c'
C:/workspace/Project/build/main\libmain.a(main.o):(.literal.app_main+0x2c): undefined reference to `start_reading'
C:/workspace/Project/build/main\libmain.a(main.o): In function `app_main':
C:/workspace/Project/main/main.c:68: undefined reference to `initialize_i2c'
C:/workspace/Project/main/main.c:69: undefined reference to `start_reading'

Then I tried to include the libmySensor.a in

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main/component.mk

with

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COMPONENT_ADD_LDFLAGS:=-L$(PROJECT_PATH)/build/mySensor/libmySensor.a

Then i get:

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LD build/sensorboard.elf
C:/workspace/Project/build/esp32\libesp32.a(cpu_start.o):(.literal.main_task+0x20): undefined reference to `app_main'
C:/workspace/Project/build/esp32\libesp32.a(cpu_start.o): In function `main_task':
C:/msys32/home/esp/esp-idf/components/esp32/cpu_start.c:463: undefined reference to `app_main'

Do I need to include something else?

Thanks!

Posted: **Tue Apr 03, 2018 11:05 am**

solved!

Problem was with a third party library which the component used.
Had to add in component.mk

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COMPONENT_ADD_LDFLAGS := -lmySensor -L$(COMPONENT_PATH)/lib -lsensorLib
COMPONENT_ADD_INCLUDEDIRS := .  lib
COMPONENT_SRCDIRS := . lib

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