Thank you for your support. I'am using a display with ST7735S driver. It seems there is no support for it yet. As an example I took SSD1289 driver. Am I right that my task is to make work the following functions (which use the functions communicating with hardware): set_cursor(GDisplay *g) set_viewport(GDisplay* g) gdisp_lld_init(GDisplay *g) Where is exactly the function sending the data to the LCD? Should I deal with dummy_read(g)? I added functions sending data and commands to board_ST7735S.h file as well as LLDSPEC void gdisp_lld_draw_pixel(GDisplay *g). Here is the part of the main() function: gfxInit(); gdispGDrawLine(g, 0,0, 128, 128, 0xFF); When I step throug the last function I achieve Hard Fault when the programm tries to reach drawpixel(g) in gdisp.c. What did I do wrong?