fix: #52. Previous fix 4e2036b was incomplete.

main.c

@@ -758,8 +758,10 @@ set_frequencies(uint32_t start, uint32_t stop, int16_t points)
 {
   int i;
   float span = stop - start;
-  for (i = 0; i < points; i++)
+  for (i = 0; i < points; i++) {
-    frequencies[i] = start + i * span / (float)(points - 1);
+    float offset = i * span / (float)(points - 1);
+    frequencies[i] = start + (uint32_t)offset;
+  }
   // disable at out of sweep range
   for (; i < sweep_points; i++)
     frequencies[i] = 0;