Can only read 16 bytes from UART1 in TM4C1230D5PM

Other Parts Discussed in Thread: TM4C1230D5PM

Hi All.

I know this question has kinda been asked before, but I could not find any clear-cut answer.

Let me explain our setup.

We have a Telit-GSM module interfaced with the TM4C1230D5PM, and this includes the interfacing of RTS/CTS pins.

In code, we have done the following ::

    /*
     * Initialize the UART1.
     */
    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_UART1);

    /*
     * Set up the RTS/CTS pins.
     */
    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
    GPIOPinConfigure(GPIO_PF0_U1RTS);
    GPIOPinConfigure(GPIO_PF1_U1CTS);
    ROM_GPIOPinTypeUART(GPIO_PORTF_BASE, GPIO_PIN_0 | GPIO_PIN_1);

    /*
     * Set up the RX/TX pins.
     */
    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOC);
    GPIOPinConfigure(GPIO_PC4_U1RX);
    GPIOPinConfigure(GPIO_PC5_U1TX);
    ROM_GPIOPinTypeUART(GPIO_PORTC_BASE, GPIO_PIN_4 | GPIO_PIN_5);

    /*
     * Configure the UART for 9600, 8-N-1 operation.
     */
    ROM_UARTConfigSetExpClk(UART1_BASE, ROM_SysCtlClockGet(), 9600,
                            (UART_CONFIG_WLEN_8 | UART_CONFIG_STOP_ONE |
                             UART_CONFIG_PAR_NONE));

    /*
     * Final UART1-initializations.
     */
    ROM_UARTFIFOEnable(UART1_BASE);
    ROM_UARTEnable(UART1_BASE);

    /*
     * Enable the interrupts (only RX).
     */
    ROM_IntEnable(INT_UART1);
    UARTIntDisable(UART1_BASE, UART_INT_TX);
    ROM_UARTIntEnable(UART1_BASE, UART_INT_RX);

Also, following is the Interrupt-Handler (UART1Handler,                      // UART1 Rx and Tx)

static void
UART1Handler(void)
{
    unsigned long interrupts;

    interrupts  = UARTIntStatus(UART1_BASE, true);
    info_log("0x%x", interrupts);
    UARTIntClear(UART1_BASE, interrupts);


    if(1)
    {
        while(ROM_UARTCharsAvail(UART1_BASE))
        {
            info_log("[%c]",  ROM_UARTCharGetNonBlocking(UART1_BASE));
            }
    }

    ROM_GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_1, GPIO_PIN_1);
    info_log("exiting");
}

("info_log" is a library function of ours, which just writes to a serial UART0 to a console).

Now, when we power on the board, we send a "AT+CGSN\r\n" command to Telit-Module (via UART1), and thereafter enter into infinite-loop in the main-thread.

Thereafter, the interrupt-handler (UART1Handler) gets called JUST ONCE, and exactly 16 bytes are read every time.

Please note that if we use any other permutation (like disabling RTS/CTS, and/or disabling interrupts), the behaviour is not consistent, and sometimes 14/15/16/17 bytes are read. With RTS/CTS enabled and interrupts enabled, we are at least getting a consistent behaviour (of exactly 16 bytes being read every time).

What needs to be done, so that the complete response can be read in a deterministic, consistent manner? I guess we need to do something extra with RTS/CTS, but can't figure it out.

Will be grateful for any pointers to hit the needle in the hay.

Thanks and Regards,

Ajay