char rotate_r(char val)
{
char a;
a= val>>1;
if (val & 0x01) // is the lsb ==1
{
a |= 0x80; //yep, pop it into the msb
}
return a;
}

Russell,
you rotate signed char in your function. Is it what you wanted?
I suppose that correct way is:

unsigned char rotate_r(unsigned char val) 
{ 
 unsigned char a; 
  a= val>>1; 
  if (val & 0x01) // is the lsb ==1 
  { 
    a |= 0x80; //yep, pop it into the msb 
  } 
  return a; 
} 

Vaclav