1  pinout Atmega328p (2x14 pins) as I2C keyboard slave
 2  ---------------------------------------------------
 3  
 4   V2                  V1              V1          V2
 5                 RESET    01        28    I2C SCL
 6   9                      02 x      27    I2C SDA
 7   8                      03 x      26 3  ROW OUT  3
 8   7                      04 x      24 2  ROW OUT  2
 9   4     ROW OUT        4 05        25 1  ROW OUT  1
10   6     COL IN         9 06 x      23 0  ROW OUT  0
11                 V3.3v    07        22    GND 
12                   GND    08        21
13                          09        20 
14                          10        19 4  COL IN
15   5     COL IN         8 11 x      18 3  COL IN
16   4     COL IN         7 12 x      17 0  COL IN
17   3     COL IN         6 13 x    x 16 1  COL IN   1
18   2     COL IN         5 14 x    x 15 2  COL IN   0
19  
20  
21  ROW and COLUMNS numbers (for V1 and V2):
22  
23    0 1 2 3 4 5 6 7 8 9
24  0 x x x x x x x x x x
25  1 x x x x x x x x x x
26  2 x x x x x x x x x x
27  3 x x x x x x x x x x
28  4 x x x x x x x x x x