This really looks promising

Demo.c

#include "Ui.h"
#include "Common.h"
#include "Communication.h"
#include "jsmn.h"

short makeApiCall(char *url, unsigned char *requestData, unsigned short requestDataLength)
{
    short sRC;
    // sRC = UIWireHttpSend(url, requestData, requestDataLength, NULL);
    sRC = UIWireHttpSend(url, requestData, requestDataLength, "Content-Type: application/json\r\n");

    if (sRC != TY_OK)
    {
        return sRC; // failed, I think
    }
    else
    {
        return TY_OK; // went well!
    }
}

short receiveApiResponse(unsigned char *responseData, unsigned short *responseLength)
{
    short sRC;
    sRC = UIWireHttpRecv(responseData, responseLength);

    if (sRC != TY_OK)
    {
        return sRC; // failed, I think
    }
    else
    {
        responseData[sizeof(responseLength)] = '\0'; // Null-terminate the response for string operations
        return TY_OK; // went well!
    }
}

const char *FetchWallet()
{
    // const char *json = "{\"name\": \"John\", \"age\": 30, \"address\": {\"street\": \"123 Main St\", \"city\": \"Example City\"}}";
    // const char *json = "{\"isSuccessful\": true, \"requestModel\": {\"requestHash\": \"363P2a88274de10b4bfc8ddc94e7a57b62b5\", \"emailAddress\": null}, \"message\": \"A verification OTP has been sent to your mobile number 345728.\", \"statusCode\": null}";

    // my code
    short sRC;
    char url[] = "https://devapi.ucard.store/identity/Agent/login/wallet/initate";
    unsigned char requestData[] = "{\"walletId\": \"5149\"}";
    unsigned short requestDataLength = strlen((char *)requestData);

    // call API
    sRC = makeApiCall(url, requestData, requestDataLength);

    unsigned char responseBuffer[4096];
    unsigned short responseLength = sizeof(responseBuffer);

    // recv data
    sRC = receiveApiResponse(responseBuffer, &responseLength);

    // Initialize jsmn parser
    jsmn_parser parser;
    jsmn_init(&parser);

    // Estimate the number of tokens needed for parsing
    int num_tokens = 20;
    jsmntok_t tokens[num_tokens];

    // Parse the JSON input
    int ret = jsmn_parse(&parser, responseBuffer, strlen(responseBuffer), tokens, num_tokens);

    if (ret < 0)
    {
        printf("Error parsing JSON: %d\n", ret);
        return NULL;
    }

    jsmntok_t *value = NULL; // Declare the value variable outside the inner loop
    // char *myName = NULL;      // Declare the variable to store the name value
    char *myHash = NULL;

    // Iterate through the JSON tokens
    for (int i = 0; i < ret; i++)
    {
        jsmntok_t *token = &tokens[i];

        // Check if token is an object
        if (token->type == JSMN_OBJECT)
        {
            // Iterate through the object's key-value pairs
            for (int j = i + 1; j < ret; j++)
            {
                jsmntok_t *key = &tokens[j];
                value = &tokens[j + 1]; // Assign value here

                // Check if key is a string
                if (key->type == JSMN_STRING)
                {
                    char key_str[key->end - key->start + 1];
                    strncpy(key_str, responseBuffer + key->start, key->end - key->start);
                    key_str[key->end - key->start] = '\0';

                    // Check if value is a string
                    if (value->type == JSMN_STRING)
                    {
                        char value_str[value->end - value->start + 1];
                        strncpy(value_str, responseBuffer + value->start, value->end - value->start);
                        value_str[value->end - value->start] = '\0';

                        // Check if the key is "name"
                        // if (strcmp(key_str, "name") == 0) {
                        //     myName = strdup(value_str); // Allocate memory and copy value
                        //     break; // Exit the inner loop once we find the name
                        // }

                        // Check if the key is "name"
                        if (strcmp(key_str, "requestHash") == 0)
                        {
                            myHash = strdup(value_str); // Allocate memory and copy value
                            break;                      // Exit the inner loop once we find the name
                        }
                    }
                }

                // Skip the value token
                j++;
            }

            // Move the main index to the end of the object
            i = value->end;
        }
    }

    // return myName;
    return myHash;
}

short TestScreen(int iTimeout)
{
    short sRC;

    const char *myReqHash = FetchWallet();

    Lib_LcdDrowArea(DEFAULT_FORG_COLOR, 0, 30, 320, 210);

    while (1)
    {
        // DRAW_TITLE("Test API");
        if (myReqHash == NULL)
        {
            DRAW_TITLE("No Response!");
        }
        else
        {
            DRAW_TITLE(myReqHash);
        }

        sRC = UIWaitKey(iTimeout, 1);
        if (UI_INPUT_TIMEOUT == sRC || UI_INPUT_CANCEL == sRC)
        {
            return sRC;
        }
        else
        {
            continue;
        }
    }
}