i2cdetect skips last address (0xff)

[RoboSchmied]

Problem

ipctool i2cdetect is always skipping the last address in its output. So i2c address 0xff is not readable with it.

root@openipc-gk7205v210:/tmp# ./ipctool i2cdetect
       0  1  2  3  4  5  6  7   8  9  a  b  c  d  e  f
    : xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  10: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  20: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  30: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  40: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  50: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  60: 60 61 xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  70: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  80: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  90: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  a0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  b0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  c0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  d0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  e0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  f0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx 

The problem is similar to #113 (but in an other function).

ipctool/src/i2cspi.c

Line 203 in cc2849e

for (i2c_addr = 0x0; i2c_addr < 0xff; ++i2c_addr) {

Solution

The solution is not as simple as #114 because the data type unsigned char used for i2caddr is always a value between 0-255 (0x00 - 0xFF). And 0xff + 1 = 0x00.
So changing the < to <=will result in an infinite loop because the condition i2c_addr <= 0xff is always true when using unsigned char.

So we have to check the condition at the end of the loop to get the desired output.

} while (i2c_addr != 0xff);

Final output:

root@openipc-gk7205v210:/tmp# ./ipctool i2cdetect
       0  1  2  3  4  5  6  7   8  9  a  b  c  d  e  f
    : xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  10: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  20: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  30: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  40: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  50: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  60: 60 61 xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  70: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  80: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  90: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  a0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  b0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  c0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  d0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  e0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |  
  f0: xx xx xx xx xx xx xx xx  xx xx xx xx xx xx xx xx  |