Polling Input Pins

Once Parapin has been initialized (Section 5), and pins have been configured as input pins (Section 6), the value being asserted by the ``far end'' can be queried using the following function:

        int pin_is_set(int pins);

Any number of pins can be queried simultaneously. The pins argument accepts the LP_PINnn constants described in Section 3. The return value is an integer in the same format. Any pins that are set (electrically high) will be set in the return value; pins that are clear (electrically low) will be clear in the return value.

Pins may only be queried if:

• They are permanent input pins (Pins 10, 11, 12, 13, and 15), as described in Section 2, or
• They are bidirectional pins previously configured as input pins, as described in Section 6.

Any query to an output pin will always return a value indicating that the pin is clear. In other words, this function can not be used to determine what value was previously asserted to an output pin.

Examples:

        pin_input_mode(LP_PIN01 | LP_DATA_PINS | LP_PIN17);
        /* Pins 1, 2-9, and 17 are now in input mode, along with
           Pins 10, 11, 12, 13, and 15, which are always inputs */

        /* check the state of pin 1 */
        printf("Pin 1 is %s!\n", pin_is_set(LP_PIN01) ? "on" : "off");

        /* check pins 2, 5, 10, and 17 - demonstrating a multiple query */
        int result = pin_is_set(LP_PIN02 | LP_PIN05 | LP_PIN10 | LP_PIN17);

        if (!result)
                printf("Pins 2, 5, 10 and 17 are all off\n");
        else {
                if (result & LP_PIN02)
                        printf("Pin 2 is high!\n");
                if (result & LP_PIN05)
                        printf("Pin 5 is high!\n");
                if (result & LP_PIN10)
                        printf("Pin 10 is high!\n");
                if (result & LP_PIN17)
                        printf("Pin 17 is high!\n");
        }