keyboard: add OLED graphics demo

reform2-keyboard-fw/kbdgfx-demo/build.sh

+#!/bin/sh
+
+gcc -O2 -o kbdgfx ./kbdgfx.c -lm
+

reform2-keyboard-fw/kbdgfx-demo/kbdgfx.c

+/*
+  kbdgfx.c -- Demo for drawing realtime graphics to the MNT Reform Keyboard
+  Copyright 2022 MNT Research GmbH (https://mntre.com)
+  License: MIT
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <math.h>
+#include <unistd.h>
+
+#define ROWS 4
+#define COLS 126
+#define BUFSZ (5+COLS*ROWS)
+#define FBUFSZ COLS*ROWS*8
+
+// our unpacked, wasteful framebuffer (one byte per pixel, 126x32)
+uint8_t fb[FBUFSZ];
+
+// the buffer we're sending to the keyboard (bit packed and column byte order)
+uint8_t buf[BUFSZ];
+
+void oled_blit(uint8_t* src, uint8_t* dst) {
+  for (int y = 0; y < ROWS; y++) {
+    // right-to-left
+    for (int x = 0; x < COLS; x++) {
+      uint8_t column = 0;
+
+      for (int z = 0; z < 8; z++) {
+        // look up the pixel
+        uint8_t bit = src[((y * 8 + 7 - z)*COLS + x)] & 1;
+
+        // bitshift the column byte to the left to make room for new pixel
+        column <<= 1;
+        // OR the bit (the pixel) to the column byte
+        column |= bit;
+      }
+
+      // store in the destination buffer
+      dst[y*COLS + x] = column;
+    }
+  }
+}
+
+// unused
+void fill_pattern(uint8_t bitpattern, uint8_t* dst) {
+  int i = 0;
+  for (int y = 0; y < 32; y++) {
+    for (int x = 0; x < COLS; x++) {
+      uint8_t pos = x % 8;
+      uint8_t b = bitpattern & (1<<pos);
+
+      dst[i++] = b ? 1 : 0;
+    }
+  }
+}
+
+void draw_sine(float t, uint8_t* dst) {
+  for (int x=0; x<126; x++) {
+    int y = 16 + sin(t + ((float)x/126.0 * 3.141))*12;
+    if (y < 0) y = 0;
+    if (y > 31) y = 31;
+
+    dst[y*COLS + x] = 1;
+  }
+}
+
+int main(int argc, char** argv) {
+  // just a counter
+  uint32_t t = 0;
+
+  if (argc < 2) {
+    printf("Usage: sudo kbdgfx /dev/hidraw0\n");
+    exit(1);
+  }
+
+  // loop forever
+  while (1) {
+    FILE* f = fopen(argv[1],"w");
+
+    if (!f) {
+      printf("Couldn't open %s!\n", argv[1]);
+      exit(1);
+    }
+
+    // start with the command
+    buf[0] = 'x';
+    buf[1] = 'W';
+    buf[2] = 'B';
+    buf[3] = 'I';
+    buf[4] = 'T';
+
+    // clear
+    memset(fb, 0, FBUFSZ);
+
+    // paint
+    draw_sine((float)t*0.03, fb);
+    draw_sine((float)t*0.05, fb);
+
+    // convert to weird OLED buffer format
+    oled_blit(fb, buf+5);
+
+    // send our buffer to the keyboard
+    fwrite(buf, BUFSZ, 1, f);
+
+    fclose(f);
+
+    // ~50 FPS
+    usleep(1000*20);
+    // ~2 FPS
+    //usleep(1000*500);
+    t++;
+  }
+}