RTOS/LAUNCHXL-CC1350: PIN driver transition timing

Hi Michael

There is no direct transition time related to the PIN driver itself, there is a small amount of checking if you use the PIN_setOutputValue() API but that is nothing that should be noticeable in this case as opening the ADC driver also takes a while. You could try using PINCC26XX_setOutputValue() API straight away, this is basically a direct hardware register write and is more efficient then the first one.

What is the configuration of the PIN you are using to drive the IRLED?

Here is the code in question:

    const PIN_Config LEDs[] =
    {
         Board_DIO22 | PIN_GPIO_OUTPUT_EN | PIN_GPIO_LOW | PIN_PUSHPULL | PIN_DRVSTR_MAX,       /* LED initially off             */
         PIN_TERMINATE
    };

//    PIN_open( &ledGroup1, LEDs );



    while(1)
    {

        Semaphore_pend( flashLEDSem, BIOS_WAIT_FOREVER );

        PIN_open( &ledGroup1, LEDs );

        //Turn IR LED on
        PIN_setOutputValue( &ledGroup1, Board_DIO22, 0x01 );

        //Give the LED a chance to turn on
        Task_sleep(500);


        //Perform conversion
        adc = ADC_open( Board_ADC0, &params );

        if (adc == NULL)
        {
            sendMessage( &uart, "ADC error", 9 );
            while (1);
        }

        res = ADC_convert( adc, &adcValue0 );

        //Turn IR LED off
        PIN_setOutputValue( &ledGroup1, Board_DIO22, 0x00 );

        ADC_close(adc);
        PIN_close( &ledGroup1 );

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Two things:
- The LED is connected to a IO with normal driver strength (4 mA). How much does the LED source?
- Does the LED itself have any turn on time?

I have torn that circuit apart now but might be revisiting it in a bit. If so, I'll check the current is within spec. But, I believe the IRLED was wired so that the port was the current sink, not the source. I couldn't find any spec in the datasheet for maximum current sink per pin, so I assumed it would be ok for the LED load. I *think* the LED resistors were 2 x 100 Ohm for a series resistance of 9.5 mA. This is all speculation (from memory) though.

With respect to LED turn on time, this is an old Radio Shack part I had lying around from a couple of years ago. I don't have a datasheet for it. However, I did Google it at the time and one of the sources at the top mention that (generically speaking) IR LEDs should have single digit nanosecond turn on time due to their physics. Even the phospher driven LEDs were much less than delay mentioned above.

So, I don't know...like I said, it's not an issue for me since the circuit that this issue is associated with is an alarm circuit...so timing isn't critical. Let's close this issue and file it under "huh...that's odd." since I no longer have that circuit constructed.