TM4C123GH6PM: Serial event handling on the TM4C123GH6PM

Hi Charles,

I was using usb-cdc, with ControlHandler, TxHandler, and RxHandler. Is there anyway to use the regular uart in this fashion, I actually just need rx handler, so I guess the example at uart_echo can be modified to suit my needs.

Another thing I am curious about is how to use the circular ring after  

cThisChar = UARTCharGet(UART0_BASE);

Best regards,

C.

can altineller said:

I was using usb-cdc, with ControlHandler, TxHandler, and RxHandler. Is there anyway to use the regular uart in this fashion, I actually just need rx handler, so I guess the example at uart_echo can be modified to suit my needs.

Hi Can,

  I'm not quite following you here. Below is the RXHandler for USB-CDC. What do you mean you want to the regular uart in this fashion? The type of message event (e.g. USB_EVENT_RX_AVAILABLE, USB_EVENT_DATA_REMAINING) that is passed to the RXHandler is specific to the USB CDC class. There is no parameter to pass to a UART ISR. You can use UARTSpaceAvail() to mimic USB_EVENT_DATA_REMAINING and UARTCharGet() to mimic USB_EVENT_RX_AVAILABLE. 

uint32_t
RxHandler(void *pvCBData, uint32_t ui32Event, uint32_t ui32MsgValue,
          void *pvMsgData)
{
    uint32_t ui32Count;

    //
    // Which event are we being sent?
    //
    switch(ui32Event)
    {
        //
        // A new packet has been received.
        //
        case USB_EVENT_RX_AVAILABLE:
        {
            //
            // Feed some characters into the UART TX FIFO and enable the
            // interrupt so we are told when there is more space.
            //
            USBUARTPrimeTransmit(USB_UART_BASE);
            MAP_UARTIntEnable(USB_UART_BASE, UART_INT_TX);
            break;
        }

        //
        // We are being asked how much unprocessed data we have still to
        // process. We return 0 if the UART is currently idle or 1 if it is
        // in the process of transmitting something. The actual number of
        // bytes in the UART FIFO is not important here, merely whether or
        // not everything previously sent to us has been transmitted.
        //
        case USB_EVENT_DATA_REMAINING:
        {
            //
            // Get the number of bytes in the buffer and add 1 if some data
            // still has to clear the transmitter.
            //
            ui32Count = MAP_UARTBusy(USB_UART_BASE) ? 1 : 0;
            return(ui32Count);
        }

        //
        // We are being asked to provide a buffer into which the next packet
        // can be read. We do not support this mode of receiving data so let
        // the driver know by returning 0. The CDC driver should not be sending
        // this message but this is included just for illustration and
        // completeness.
        //
        case USB_EVENT_REQUEST_BUFFER:
        {
            return(0);
        }

        //
        // We don't expect to receive any other events.  Ignore any that show
        // up in a release build or hang in a debug build.
        //
        default:
#ifdef DEBUG
            while(1);
#else
            break;
#endif
    }

    return(0);
}

Hello Charles,

What I meant was: The usb-cdc example, along with many other datastructures, uses an interrupt handler so when a packet is received RxHandler gets called. The non-cdc uart examples, do work by polling in a loop to detect incoming data. Am I wrong? Or behind the code usb-cdc examples too work by polling?

Best Regards,

Can