Edit: Solved
I'm using an external makefile - a modified version taken from the LUFA VirtualSerial demo.
It uses the compiler option: "CFLAGS += -funsigned-char" which tells the compiler use unsigned char by default.
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I'm using Studio5 version 5.1.208.
I thought that char was signed 8-bit type by default, but when using itoa() it seems to be unsigned unless explicitly declared as signed.
Here's the code:
void TestBits(void)
{
ShowBits(-128);
ShowBits(-1);
ShowBits(0);
ShowBits(1);
ShowBits(127);
}
void ShowBits(signed char Num)
{
char i;
char Buffer[9] = " ";
char NumStr[9] = " ";
itoa((int)Num, NumStr, 10);
for(i=0; i<8; i++) {
if (Num & (1 << i))
Buffer[7-i] = '1';
else Buffer[7-i] = '0';
}
fputs("\n\r", &USBSerialStream);
fputs(NumStr, &USBSerialStream);
fputs(" = ", &USBSerialStream);
fputs(Buffer, &USBSerialStream);
fputs("\n\r", &USBSerialStream);
}
And here's the results:
Using: void ShowBits(char Num) 128 = 10000000 255 = 11111111 0 = 00000000 1 = 00000001 127 = 01111111 Using: void ShowBits(signed char Num) -128 = 10000000 -1 = 11111111 0 = 00000000 1 = 00000001 127 = 01111111
The only difference between the two runs was changing char to signed char.
Did I get it backwards all these years?
