diff --git a/V203F6P6/ws2812b/linux/Makefile b/V203F6P6/ws2812b/linux/Makefile
index 4eece2a..9ad0ad9 100644
--- a/V203F6P6/ws2812b/linux/Makefile
+++ b/V203F6P6/ws2812b/linux/Makefile
@@ -1,9 +1,10 @@
 CC = gcc
 CX = g++
 LD = ld
-CFLAGS = -c -Os -fPIC
+VPATH  = . ..
+CFLAGS = -c -Os -fPIC -I../ -I../common
 
-OBJS = main.o
+OBJS = main.o ws2812b.o
 SLIB = graph.so
 
 all: $(SLIB)
diff --git a/V203F6P6/ws2812b/linux/graph.py b/V203F6P6/ws2812b/linux/graph.py
index ea1b4e1..34d7066 100755
--- a/V203F6P6/ws2812b/linux/graph.py
+++ b/V203F6P6/ws2812b/linux/graph.py
@@ -5,6 +5,7 @@ import cffi
 import numpy as np
 import matplotlib.pyplot as plt
 c_header = '''
+void   test (void);
 void   print_table  (void);
 double ComputeRed   (double);
 double ComputeGreen (double);
@@ -25,16 +26,17 @@ def plot_colors(C):
   plt.grid()
   plt.ylabel('Intenzity')
   plt.xlabel('N')
-  #plt.savefig('color.png')
-  plt.show()
+  plt.savefig('color.png')
+  #plt.show()
   
 ############################  MAIN  ##############################################################
 def main_func():
   ffi = cffi.FFI()
   ffi.cdef(c_header)
   C = ffi.dlopen("./graph.so")
+  C.test()
   plot_colors(C)
-  #C.print_table()
+  C.print_table()
   ffi.dlclose(C)
   return True
 if __name__ == '__main__':
diff --git a/V203F6P6/ws2812b/linux/main.cpp b/V203F6P6/ws2812b/linux/main.cpp
index 2d60eec..733f643 100644
--- a/V203F6P6/ws2812b/linux/main.cpp
+++ b/V203F6P6/ws2812b/linux/main.cpp
@@ -1,20 +1,22 @@
 #include <stdint.h>
 #include <cmath>
 #include <cstdio>
+#include "ws2812b.h"
 extern "C" {
+  extern void   test         (void);
   extern void   print_table  (void);
   extern double ComputeRed   (double);
   extern double ComputeGreen (double);
   extern double ComputeBlue  (double);
 };
-union Color {
+union MColor {
   struct _c {
     uint8_t g, r, b, a;
     explicit _c (const uint8_t _r, const uint8_t _g, const uint8_t _b) noexcept :
                 g(_g), r(_r), b(_b), a(0u) {}
   } c;
   uint32_t number;
-  explicit Color (const uint8_t r, const uint8_t g, const uint8_t b) : c(r, g, b) {}
+  explicit MColor (const uint8_t r, const uint8_t g, const uint8_t b) : c(r, g, b) {}
 };
 #if 0
 static Color getColor (const int index) {
@@ -38,25 +40,25 @@ static uint8_t Gauss (const double x, const double x0) {
   double r = 256.0 * exp (-sigma * arg * arg);
   return uint8_t (r);
 }
-static Color getColor (const int index) {
+static MColor getColor (const int index) {
   uint8_t  r=0,g=0,b=0;                  // proměnné barvy
   r = Gauss(index, 85.333);
   g = Gauss(index, 170.67);
   b = Gauss(index,   0.01) + Gauss(index, 256.0);
-  Color color(r, g, b);
+  MColor color(r, g, b);
   return color;
 }
 #endif
 double ComputeRed   (double x) {
-  Color c = getColor(x);
+  MColor c = getColor(x);
   return double (c.c.r);
 }
 double ComputeGreen (double x) {
-  Color c = getColor(x);
+  MColor c = getColor(x);
   return double (c.c.g);
 }
 double ComputeBlue  (double x) {
-  Color c = getColor(x);
+  MColor c = getColor(x);
   return double (c.c.b);
 }
 
@@ -66,9 +68,42 @@ void print_table () {
   fprintf(out, "const unsigned table [] = {");
   for (unsigned n=0u; n<256u; n++) {
     if ((n%8) == 0u) fprintf(out, "\n");
-    const Color c = getColor(n);
+    const MColor c = getColor(n);
     fprintf(out, "  0x%06X,", c.number);
   }
   fprintf(out, "\n};\n");
   fclose(out);
 }
+
+static constexpr unsigned PADDING  = 10      * sizeof (Color);
+static constexpr unsigned LEDS_LEN = NUMLEDS * sizeof (Color);
+static constexpr unsigned FULL_LEN = PADDING + LEDS_LEN;
+static uint8_t buffer [FULL_LEN];
+void test () {
+  printf ("led color size = %zd\n", sizeof (Color));
+  for (unsigned n=0; n<FULL_LEN; n++) buffer[n] = 0;
+  Color * const cptr = reinterpret_cast<Color*>(buffer + PADDING);
+  for (unsigned n=0; n<NUMLEDS; n++) {
+    Color & c = cptr [n];
+    const OneColor cb (0xff), cg (0x55), cr (0x00);
+    c.b = cb; c.g = cg; c.r = cr;
+  }
+  const unsigned mlen = 1024;
+  char text [mlen];
+  for (unsigned n=0; n<NUMLEDS; n++) {
+    Color & c = cptr [n];
+    unsigned k = 0u;
+    k += c.g.to_string(text + k);
+    text [k++] = '|';
+    k += c.r.to_string(text + k);
+    text [k++] = '|';
+    k += c.b.to_string(text + k);
+    printf("led %d => %s\n", n, text);
+  }
+  printf("buffer dump :");
+  for (unsigned n=0; n<FULL_LEN; n++) {
+    if ((n%10) == 0) printf("\n");
+    printf("<%02x>", buffer[n]);
+  }
+  printf("\n");
+}
diff --git a/V203F6P6/ws2812b/table.c b/V203F6P6/ws2812b/table.c
index 1b098e7..1c9da88 100644
--- a/V203F6P6/ws2812b/table.c
+++ b/V203F6P6/ws2812b/table.c
@@ -2,13 +2,13 @@ const unsigned table [] = {
   0xFF0700,  0xFF0700,  0xFF0800,  0xFE0900,  0xFE0A00,  0xFC0A00,  0xFB0B00,  0xF90C00,
   0xF80D00,  0xF60E00,  0xF31000,  0xF11100,  0xEE1200,  0xEB1300,  0xE81500,  0xE51600,
   0xE11800,  0xDE1A00,  0xDA1B00,  0xD61D00,  0xD21F00,  0xCE2100,  0xCA2400,  0xC52600,
-  0xC12800,  0xBC2B00,  0xB82D00,  0xB33000,  0xAE3300,  0xA93600,  0xA43900,  0xA03C00,
-  0x9B3F00,  0x964300,  0x914600,  0x8C4A00,  0x874E00,  0x835100,  0x7E5500,  0x795900,
+  0xC12800,  0xBC2B00,  0xB82D00,  0xB33000,  0xAE3300,  0xA93600,  0xA53900,  0xA03C00,
+  0x9B3F00,  0x964300,  0x914600,  0x8C4A00,  0x884E00,  0x835100,  0x7E5500,  0x795900,
   0x755D00,  0x706200,  0x6C6600,  0x676A00,  0x636F00,  0x5F7300,  0x5B7800,  0x577C00,
   0x538100,  0x4F8600,  0x4B8B00,  0x478F00,  0x449400,  0x409900,  0x3D9E00,  0x3AA300,
   0x37A800,  0x34AC00,  0x31B100,  0x2EB600,  0x2CBB00,  0x29BF00,  0x27C400,  0x24C800,
-  0x22CD00,  0x20D101,  0x1ED501,  0x1CD901,  0x1ADD01,  0x19E001,  0x17E401,  0x15E702,
-  0x14EA02,  0x12ED02,  0x11F002,  0x10F302,  0x0FF503,  0x0EF703,  0x0DF903,  0x0CFB04,
+  0x22CC00,  0x20D101,  0x1ED501,  0x1CD901,  0x1ADD01,  0x19E001,  0x17E401,  0x15E702,
+  0x14EA02,  0x12ED02,  0x11F002,  0x10F202,  0x0FF503,  0x0EF703,  0x0DF903,  0x0CFB04,
   0x0BFC04,  0x0AFD05,  0x09FE05,  0x08FF06,  0x08FF06,  0x07FF07,  0x06FF07,  0x06FF08,
   0x05FF09,  0x05FE09,  0x04FD0A,  0x04FC0B,  0x04FA0C,  0x03F80D,  0x03F60E,  0x03F40F,
   0x02F210,  0x02EF12,  0x02EC13,  0x02E914,  0x01E616,  0x01E317,  0x01DF19,  0x01DB1B,
@@ -17,7 +17,7 @@ const unsigned table [] = {
   0x008E49,  0x00894C,  0x008450,  0x008054,  0x007B58,  0x00765C,  0x007260,  0x006D64,
   0x006969,  0x00646D,  0x006072,  0x005C76,  0x00587B,  0x005480,  0x005084,  0x004C89,
   0x00498E,  0x004593,  0x004298,  0x003E9C,  0x003BA1,  0x0038A6,  0x0035AB,  0x0032B0,
-  0x002FB4,  0x002CB9,  0x002ABE,  0x0027C2,  0x0025C7,  0x0023CB,  0x0121CF,  0x011FD3,
+  0x002FB4,  0x002DB9,  0x002ABE,  0x0027C2,  0x0025C7,  0x0023CB,  0x0121CF,  0x011FD3,
   0x011DD7,  0x011BDB,  0x0119DF,  0x0117E3,  0x0116E6,  0x0214E9,  0x0213EC,  0x0212EF,
   0x0210F2,  0x030FF4,  0x030EF6,  0x030DF8,  0x040CFA,  0x040BFC,  0x040AFD,  0x0509FE,
   0x0509FF,  0x0608FF,  0x0607FF,  0x0707FF,  0x0806FF,  0x0806FF,  0x0905FE,  0x0A05FD,
diff --git a/V203F6P6/ws2812b/ws2812b.h b/V203F6P6/ws2812b/ws2812b.h
index d571cd2..326dac3 100644
--- a/V203F6P6/ws2812b/ws2812b.h
+++ b/V203F6P6/ws2812b/ws2812b.h
@@ -38,8 +38,11 @@ static constexpr unsigned FIFOLEN = 8u;  // min. depth je 8, jinak mocnina 2 >=
  * pořád, v 1. části  dělá "reset", tedy časování rámce (vysílá nuly).
  * V 2. části si vybere z fronty ring data a uloží je do buferu ve správném
  * tvaru. Využívá se toho, že přerušení přijde až na konci a naplnění daty
- * netrvá dlouho, takže se přepisuje jen část, která se nevysílá.
+ * netrvá dlouho, takže se přepisuje jen část, která se právě nevysílá.
  * Fronta byla použita (celkem zbytečně) protože zatím netuším jaká data posílat.
+ * NOTE
+ * Protože WS2812B je 5V záležitost a procesor je napájen jen 3.3V, funguje to
+ * na hraně a je dobré zapojit mezi MOSI a +5V rezistor 1k. Je to pak stabilnější.
  * */
 class ws2812b : public OneWay<uint8_t> {
   FIFO<uint32_t,FIFOLEN> & ring;