Linking failure on 0.3.1 with nRF52

[WillyJL]

I am porting Meshtastic firmware from PCF8563_Library to SensorLib (meshtastic/firmware#8061), it works well on ESP32, however the same code fails linking on nRF52 platform:

Linking .pio/build/t-echo/firmware.elf
/home/user/.platformio/packages/toolchain-gccarmnoneeabi@1.90301.200702/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/bin/ld: .pio/build/t-echo/src/gps/RTC.cpp.o: in function `readFromRTC()':
/home/user/Git/meshtastic-firmware/src/gps/RTC.cpp:106: undefined reference to `PCF8563Constants::PCF8563_SLAVE_ADDRESS'
/home/user/.platformio/packages/toolchain-gccarmnoneeabi@1.90301.200702/bin/../lib/gcc/arm-none-eabi/9.3.1/../../../../arm-none-eabi/bin/ld: .pio/build/t-echo/src/gps/RTC.cpp.o: in function `SensorPCF8563::setDateTime(RTC_DateTime)':
/home/user/Git/meshtastic-firmware/.pio/libdeps/t-echo/SensorLib/src/SensorPCF8563.hpp:116: undefined reference to `PCF8563Constants::PCF8563_SLAVE_ADDRESS'
collect2: error: ld returned 1 exit status

I was able to compile by changing this line:

SensorLib/src/REG/PCF8563Constants.h

Line 40 in 769b484

static constexpr uint8_t PCF8563_SLAVE_ADDRESS = 0x51;

to

const uint8_t PCF8563_SLAVE_ADDRESS = 0x51;

but I'm guessing this means that the data is stored physically in the class vtable instead of being compiled in the code that uses it as a literal value, which means more flash usage, so not an ideal fix. Any help is appreciated.

Also, considering #22 reported something similar, I assume it is the same issue and it affects all the other src/REG/*Constants.h files.

[lewisxhe]

https://github.com/lewisxhe/SensorLib/actions/runs/17004214129/job/48211478596#step:10:442
The strange thing is that all online builds on GitHub are successful. In order to be compatible with older versions of the compiler, I'd better change the variable to const.

[lewisxhe]

Changing SensorLib@0.3.1 to SensorLib@0.3.2 will allow it to compile successfully in meshtastic.

[lewisxhe]

A small suggestion:
You can use the SensorRtcHelper object without distinguishing whether you are using PCF85063 or PCF8563
https://github.com/lewisxhe/SensorLib/blob/master/examples/SensorRtcHelperExamples/SensorRtcHelperExamples.ino

[WillyJL]

thank you! meshtastic does its own i2c "scanning" so its a bit convoluted looking both for a specific i2c address based on a #define, and then using SensorRtcHelper to scan that way, but it works.