Einfaches Snippet das einen im Binärfile hinterlegten BMP Font(RGB565) im Framebuffer scrollt. Jeder Buchstabe hat in der Datei seinen Startblock Ascii-Code*Width*Heigth und jede Fontgröße wiederum ihren Startblock. (Gepackt mit einem kleinen Tool für Grafiken in SPI-Flashes)

Als Grundlage installiert man rpi-update mit integriertem fbtft und aktiviert SPI.

Dann kann man zB. für das kleine HY28B display folgend Treiber laden:

modprobe dma fbtft

modprobe fbtft_device name=hy28b fbtft_device.speed=10000000 fbtft_device.rotate=90 fbtft_device.mode=3

//#include "font.h"
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/fb.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <string.h>
#include <fstream>
using namespace std;
unsigned int BinToNum(char* b, int bytes)
{
    unsigned int tmpx = 0;
    unsigned int pw = 1;
    for (int i = 0; i < bytes; i++)
    {
        tmpx += ((unsigned char)b[i] * pw);
        pw = pw * 256;
    }
    return tmpx;
}
int width = 320;
int height = 240;
int ColorBits = 16;
int size = 0;
unsigned short int* matrix;
char* fbp = 0;
int x = 0, y = 0;
long int location = 0;
int fbfd = 0;
struct fb_var_screeninfo vinfo;
struct fb_fix_screeninfo finfo;
long int screensize = 0;

// Liest MultiImageDatei in Array ein, Buchstaben in verschiedenen Groessen
// jeweils nach Ascii-Code sortiert.
int Open(const char* path)
{
    int pad = 0;
    unsigned int sof = 0;
    unsigned int tx = 0;
    char tmp[4] = { 0, 0, 0, 0 };
    fstream file;
    file.open(path, ios::in);
    if (file.fail())
    {
        width = height = ColorBits = size = 0;
        return -1;
    }
    else
    {
        printf("The Filesizen");
        file.seekg(0, file.end);
        size = file.tellg();
        // Initialize Matrix//
        printf("The Filematrixn");
        matrix = new (unsigned short int[size / 2]);
        sof = 0;
        int counter = 0;
        while (sof < size)
        {
            file.seekg(sof, ios::beg);
            file.read(tmp, (int)(ColorBits / 8));
            tx = BinToNum(tmp, (int)(ColorBits / 8));
            matrix[counter] = tx;
            sof += (int)(ColorBits / 8);
            counter++;
        }
        file.close();
        return 1;
    }
}
// Framebuffer Ausschnitte auf Framebuffer selbst kopieren(Scrolling Ansatz)
int blockcpfb(int source_x, int source_y, int width, int height, int dest_x, int dest_y)
{
    for (int y = 0; y < height; y++)
        for (int x = 0; x < width; x++)
        {
            location = (source_x + x) * (vinfo.bits_per_pixel / 8) + (source_y + y) * 640;

            unsigned short int t = *((unsigned short int*)(fbp + location));
            location = (dest_x + x) * (vinfo.bits_per_pixel / 8) + (dest_y + y) * 640;
            *((unsigned short int*)(fbp + location)) = t;
        }
}
// Kopiert Image/Buchstabe ueber  Startblock aus Tabelle von array in
// Framebuffer
int blockcp(int start, int width, int height, int dest_x, int dest_y)
{
    for (int y = 0; y < height; y++)
        for (int x = 0; x < width; x++)
        {
            location = (dest_x + x) * (vinfo.bits_per_pixel / 8) + (dest_y + y) * 640;
            unsigned short int t = matrix[(y * width) + start + x];

            *((unsigned short int*)(fbp + location)) = t;
        }
}
// schneidet aus dem angegebenem Bildsource aus dem Array einen Bereich aus.
int blockcpclipping(int start, int width, int height, int dest_x, int dest_y, int clipx, int clipy,
    int clipwidth, int clipheight)
{
    for (int y = 0; y < height; y++)
        for (int x = 0; x < width; x++)
        {
            if (x > clipx && y > clipy && x < clipx + clipwidth && y < clipy + clipheight)
            {
                location = (dest_x + x) * (vinfo.bits_per_pixel / 8) + (dest_y + y) * 640;
                unsigned short int t = matrix[(y * width) + start + x];

                *((unsigned short int*)(fbp + location)) = t;
            }
        }
}

// munmap(fbp, screensize);
int main()
{
    // Open the file for reading and writing
    fbfd = open("/dev/fb1", O_RDWR);
    if (fbfd == -1)
    {
        perror("Error: cannot open framebuffer device");
        exit(1);
    }
    printf("The framebuffer device was opened successfully.n");
    // Get fixed screen information
    if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo) == -1)
    {
        perror("Error reading fixed information");
        exit(2);
    }
    // Get variable screen information
    if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo) == -1)
    {
        perror("Error reading variable information");
        exit(3);
    }
    printf("%dx%d, %dbppn", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);
    // Figure out the size of the screen in bytes
    screensize = vinfo.xres * vinfo.yres * vinfo.bits_per_pixel / 8;
    // Map the device to memory
    fbp = (char*)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0);
    if ((int)fbp == -1)
    {
        perror("Error: failed to map framebuffer device to memory");
        exit(4);
    }
    printf("The framebuffer device was mapped to memory successfully.n");
    x = 320;
    y = 240;
    // Where we are going to put the pixel
    // Figure out where in memory to put the pixel
    if (Open("font.bin") == 1)
    {
    }

    string s = " Guns n Roses ";
    int z = 0;

    for (int c = 0; c <= ((int)s.length() - 4); c++)
    {
        string tmp = s.substr(c, 4);
        string::iterator i;

        for (i = tmp.begin(); i != tmp.end(); i++)
        {
            // berechnet Startblock aus Ascii Code und kopiert Buchstaben.
            blockcp((8330 * (((int)*i) - 32)), 70, 119, 40 + z * 70, 0);
            z++;
        }
    }
    int charspalte = 1;
    int mychar = 0;
    z = 70;
    char tmp = s.at(mychar);
    while (1)
    {
        blockcpfb(1, 0, 319, 119, 0, 0);
        //Einzelne Linien dem Scroll folgend einkopieren(Neuer Buchstabe erscheint komplett)
        // blockcpclipping( (8330*(((int)tmp)-32)),70, 119,320,
        // 0,charspalte,0,1,119);

        if (z == 70)
        {
            char tmp = s.at(mychar);
            blockcp((8330 * (((int)tmp) - 32)), 70, 119, 320 - 70, 0);
            z = 0;
            mychar++;
            charspalte = 1;
            if (mychar == s.length())
            {
                mychar = 0;
            }
        }
        else
        {
            charspalte++;
            z++;
        }
    }

    close(fbfd);
    return 0;
}