Issue linking local libraries

Development Platforms
1

Hi there!

I’m having trouble linking a local library that I wrote:

C:/Users/<user>/.platformio/packages/toolchain-rp2040-earlephilhower/bin/../lib/gcc/arm-none-eabi/14.3.0/../../../../arm-none-eabi/bin/ld.exe: .pio\build\default\src\main.cpp.o: in function `setup': 
main.cpp:(.text.setup+0x6): undefined reference to `_ZN6Bme280C1Eh'

My project structure looks like this:

|- platformio.ini
|-- src
|  |-- main.cpp
|-- lib
|  |-- i2c
|  |  |-- src
|  |  |  |-- bme280.cpp
|  |  |  |-- bme280.h
|  |  |  |-- i2c.cpp
|  |  |  |-- i2c.h
|  |  |-- library.json
...

platformio.ini:

[env]
platform = https://github.com/maxgerhardt/platform-raspberrypi.git
board = adafruit_feather_thinkink
framework = arduino

[env:default]
lib_deps =
    adafruit/Adafruit NeoPixel@^1.15.2
    symlink://lib/i2c

main.cpp:

#include <Arduino.h>
#include <bme280.h>

void setup() {
  Bme280 bme;

  bme.reset();

  byte* chipId = bme.readBytes(0xD0, 1);
  Serial.printf("chip id: %d\n", chipId);
  delete chipId;
}

void loop() {

}

bme280.h:

// bme280.h contains header code for the BME280 sensor from bosch
#ifndef BME280_H
#define BME280_H

#include "i2c.h"

#define BME280_ADDR 0x76
#define BME280_ADDR_ALT 0x77

class Bme280 : public I2C {
    public:
        Bme280(byte addr = BME280_ADDR);

        void reset() override;
};

#endif

bme280.cpp:

// bme280.cpp contains implementation code for the BME280 sensor from bosch
#include "bme280.h"

// Performs a soft reset
void Bme280::reset() {
    Wire.beginTransmission(this->addr);

    // Register is 0xE0
    Wire.write(0xE0);
    // Command to reset is 0xB6
    Wire.write(0xB6);

    byte out = Wire.endTransmission();
    if (out) {
        Serial.printf("Reset returned code: %d\n", out);
    }
}

i2c.h:

// i2c.h contains header code for interfacing with i2c devices
#ifndef I2C_H
#define I2C_H

#include <Arduino.h>
#include <Wire.h>

#define WRITE_MODE 0x00
#define READ_MODE 0x80

class I2C {
    public:
        I2C(byte addr);

        virtual void reset() = 0;
        virtual byte* readBytes(uint registerAddr, uint numBytes);
    protected:
        byte addr;
};

#endif

i2c.cpp:

// i2c.cpp contains implementation code for interfacing with i2c devices
#include "i2c.h"

I2C::I2C(byte addr) {
    this->addr = addr;

    Wire.begin();
    Serial.begin();
    while(!Serial);
}

// Read bytes from a register
byte* I2C::readBytes(uint registerAddr, uint numBytes) {
    // Read chip id
    Wire.beginTransmission(this->addr);

    // Which register to read
    Wire.write(registerAddr);

    byte out = Wire.endTransmission();
    if (out) {
        Serial.printf("Failed to write with error code %d\n", out);
        return NULL;
    }

    Wire.beginTransmission(this->addr | READ_MODE);

    out = Wire.endTransmission();
    if (out) {
        Serial.printf("Failed to read with error code %d\n", out);
        return NULL;
    }

    Wire.requestFrom(this->addr, numBytes);

    byte* returnArray = new byte[numBytes];
    for (int i = 0; i < numBytes && Wire.available(); i++) {
        byte b = Wire.read();
    }

    return returnArray;
}

It does seem to be seeing all my files:

Compiling .pio\build\default\lib5c9\i2c\bme280.cpp.o
Compiling .pio\build\default\lib5c9\i2c\i2c.cpp.o
...
Archiving .pio\build\default\lib5c9\libi2c.a

I’m sure I’m missing something simple as it’s also been years since I’ve written c++, but I set up my project folder as best I could, following the docs. Does anyone have any ideas?

2

The error means that your Bme280 class is missing the definition of the constructor.
Adding this line to bme280.cpp will fix the error:

Bme280::Bme280(byte addr) : I2C(addr) {}

Remove this line!
The library is already located inside the project folder.

Only use symlink if it is a global library located outside the project directory.
For example see this post: Include search path redundency platformio.ini and vscode settings include path - #2 by sivar2311