Include one character with two digit value - c

Question

The code below show, to check the digital output at PORTB on the hardware. That PORTB have UI1-UI12.
When it is not shorted, the value will be 1.
So if nothing shorted, when i write UI5-UI7 in Hyperterminal it will show 0x03 (111bit in binary)
Here the code:
void decode(unsigned char* msg) {
AD1PCFGL = 0xFFFF; //set all analog pin to digital
int y, z, x;
unsigned char* lala[50];
if (strstr(msg, "UI") == msg) {//UI[2]-UI[6]
x = msg[2] - '0'; // char to integer
y = msg[6] - '0'; // char to integer
//UI[2]-UI[6]
int start = x - 1; //get offset, start from zero
int end = y; // end
int pinValue; // each pin value
int output_value=0; // result
int j = 0, i; // j, start from 0
for (i = start; i < end; i++) {
pinValue = ((PORTB & (1 << i)) > 0 )?1:0; // get current pin value from RB3, RB4, RB5, RB6, RB7->UI4, UI5, UI6, UI7, UI8
output_value |= (pinValue << j++);
}
sprintf(lala, "0x%X \r\n", output_value); //%02x(hex),%X(HEX)
sendString(lala);// send to Hyper-Terminal
}
}
How to include msg[2] and msg[6] with two digits number ?
Because, from the above code, there was problem when i write UI10-UI12, it give the wrong result.

Answer 1

If the input is always in the same format, it's simple to use e.g. strtok to split the input into the two parts, and then use strtol to convert the numbers to integers.
Something like this perhaps:
char *start_string = strtok(msg, "-");
char *end_string = strtok(NULL, "-");
int start = strtol(start_string + 2, NULL, 10);
int end = strtol(end_string + 2, NULL, 10);