Array itself is the one index of an 2d array ie, strings[i][so_far[i]]

[saramah]

hI,

When I was terying to understand the tutorials from

https://circuitdigest.com/microcontroller-projects/gsm-interfacing-with-pic16f877a

, the below 2d array is found.

if (strings[i][so_far[i]] == received)

.

what i understand, it is a 2-D array, and 'so_far[]' array itself is one of the another index of 'string' array. But my qestion is how this operate in the code below as mentioned in the aricle:

/*
#define SIM900_OK 1
#define SIM900_READY 2
#define SIM900_FAIL 3
#define SIM900_RING 4
#define SIM900_NC 5
#define SIM900_UNLINK 6
*/
inline unsigned char _SIM900_waitResponse(void) 
{
    unsigned char so_far[6] = {0,0,0,0,0,0};
    unsigned const char lengths[6] = {2,12,5,4,6,6};
    unsigned const char* strings[6] = {"OK", "+CPIN: READY", "ERROR", "RING", "NO CARRIER", "Unlink"};
    unsigned const char responses[6] = {SIM900_OK, SIM900_READY, SIM900_FAIL, SIM900_RING, SIM900_NC, SIM900_UNLINK};
    unsigned char received;
    unsigned char response;
    char continue_loop = 1;
    while (continue_loop) 
    {
        received = _SIM900_getch();
        for (unsigned char i = 0; i < 6; i++) 
        {
            if (strings[i][so_far[i]] == received) 
            {
                so_far[i]++;
                if (so_far[i] == lengths[i]) 
                {
                    response = responses[i];
                    continue_loop = 0;
                }
            } 
            
            else
            {
                so_far[i] = 0;
            }
        }
    }
    return response;
}

how //if (strings[so_far] == received) this line being implemented. if i had been recived "O" for "OK" at 'received' variable from calling fun //_SIM900_getch();
I REQUEST TO MAKE ME UNDERSTAND IF POSSIBLE..
TNX

 

[FvM]

The code is receiving input from the GSM modem and staying in the loop until one of the six expected responses in strings[] is detected.

so_far[] keeps track of the already matched characters in each compare string.

For the details, you should review the string processing chapter in a C programming text book.