U8G2 KEIL ARM LPC17xx

[pal73]

I need to connect a OLED SSD1306 to a LPC17xx in a project on KEIL ARM using your wonderful library. It is really wonderful how it works in Arduino. But in my case I broke my head. But all to no avail. Please help me understand.
How to connect library to a C project? I take the CSRC folder, make it visible for include, in the main file I do #include "u8g2.h". And what to do with the C files? Connect them all to the project? Then when compiling I get an error that about 200 KB is missing. I don't believe that there is at least one Arduino with such a memory capacity. Apparently including all files is not the right strategy. But which ones? It is not clear from your description. Or I can't read

[olikraus]

Let my try to answer your questions step by step.

How to connect library to a C project? I take the CSRC folder, make it visible for include, in the main file I do #include "u8g2.h".

Yes exactly, you just copy everything from the csrc folder. There is a step by step instruction for Atmel Studio, but the concept should be the same for you: https://github.com/olikraus/u8g2/wiki/u8g2as7

Along with the csrc you also need one (or two) extra functions, which will handle the communication with you LPC17xx. I suggest to start with a simple software emulated SPI or I2C interface. In such a case you just need a GPIO and delay callback: https://github.com/olikraus/u8g2/wiki/Porting-to-new-MCU-platform#the-uc-specific-gpio-and-delay-callback

I have once created such a callback for the LPC8xx: https://github.com/olikraus/u8g2/blob/master/sys/arm/lpc824/u8g2_logo/u8x8cb.c

If you need more performance, then the second callback is required, which will do the transfer on a byte level. It is implemented here: https://github.com/olikraus/lpc804_plu/blob/a12203333f4fc58de74816a4ed0ae59f5d56f5cc/lpc804/u8g2_logo/u8x8cb.c#L138

More detailes are here: https://github.com/olikraus/u8g2/wiki/Porting-to-new-MCU-platform#communication-callback-eg-u8x8_byte_hw_i2c

You could also search here in the issues. For example here: #297

Then when compiling I get an error that about 200 KB is missing.

You need to activate the linker garbage collection, maybe also called LTO (link time optimization). In fact Arduino relies on this gcc feature a lot. Actually this is not even an optimization, it just removes code and data which is not used in your project.
In many community versions of professional compilers, this is disabled, so please ensure that you have a proper compiler. In many cases this also needs to be enabled (but I don't know the KEIL options for this).

You could try to do this without LTO:
Remove all u8x8_d_xxx files which you don't need, so just keep the u8x8_d_ssd1306_xxx.c
For the u8g2_fonts.c, extract exactly the font you need manually, paste the font array into your main code and then remove u8g2_fonts.c.
This should bring you down to a fitting size of the code.

[pal73]

Thank you very much for your detailed and quick response. I will dedicate today to trying to follow your advice. Although, to be honest, I was already going to get from my old LPC-projects the software implementation of I2C and software filling of the screen buffer with character rasters (also generated at one time in a self-written character generator). Thank you!