example of LPUART for MAX78000?

[khavernathy]

Hi, I see an example of using UART for the MAX78000, but can I see one for LPUART? I guess I need to change some parameters, for example the clock selection.

Is there a cap on baud-rate for the LPUART?

Are there any other special considerations I should have in mind when writing code for it?

Currently my application gets stuck in an infinite loop here, in .../MaximSDK/Libraries/PeriphDrivers/Source/UART/uart_ai85.c

    if (freq > 0) {
        // Enable baud clock and wait for it to become ready.
        uart->ctrl |= MXC_F_UART_CTRL_BCLKEN;
        while (((uart->ctrl & MXC_F_UART_CTRL_BCLKRDY) >> MXC_F_UART_CTRL_BCLKRDY_POS) == 0) {}
    }

after a call to
error = MXC_UART_Init(MXC_UART_GET_UART(3), 9600, MXC_UART_IBRO_CLK);

I have the same inf loop issue when i try MXC_UART_ERTCO_CLK as well.

[khavernathy]

More context here on how I'm initializing the UART. I'm using a MAX78000 FTHR.

void UART_Handler(void) {MXC_UART_AsyncHandler(MXC_UART_GET_UART(SIG_UART));}
void readCallback(mxc_uart_req_t* req, int error) {READ_FLAG = error;LED_Toggle(LED2);}

void uart_init() {

    // set P0.16 and P0.17 as GPIO "inputs" so they remain high impedance and don't interfere with LPUART.
    // TODO: do this properly somehow.
    mxc_gpio_cfg_t fakeGPIO;
    fakeGPIO.port = MXC_GPIO0;
    fakeGPIO.mask = MXC_GPIO_PIN_16;
    fakeGPIO.pad  = MXC_GPIO_PAD_NONE; // neither pull-up nor pull-down
    fakeGPIO.func = MXC_GPIO_FUNC_IN; // as input
    fakeGPIO.vssel= MXC_GPIO_VSSEL_VDDIOH; //voltage on pin set to 3.3v,
    mxc_gpio_cfg_t fakeGPIO2;
    fakeGPIO2.port = MXC_GPIO0;
    fakeGPIO2.mask = MXC_GPIO_PIN_17;
    fakeGPIO2.pad  = MXC_GPIO_PAD_NONE;
    fakeGPIO2.func = MXC_GPIO_FUNC_IN;
    fakeGPIO2.vssel= MXC_GPIO_VSSEL_VDDIOH; //voltage on pin set to 3.3v,
    MXC_GPIO_Config(&fakeGPIO);
    MXC_GPIO_Config(&fakeGPIO2);

    //UART init
    int error;

    NVIC_ClearPendingIRQ(MXC_UART_GET_IRQ(SIG_UART));
    NVIC_DisableIRQ(MXC_UART_GET_IRQ(SIG_UART));
    MXC_NVIC_SetVector(MXC_UART_GET_IRQ(SIG_UART), UART_Handler);
    NVIC_EnableIRQ(MXC_UART_GET_IRQ(SIG_UART));

    // use MXC_UART_ERTCO_CLK or MXC_UART_IBRO_CLK for UART3 (LPUART); MXC_UART_IBRO_CLK for UART0.
    error = MXC_UART_Init(MXC_UART_GET_UART(SIG_UART), UART_BAUD, MXC_UART_IBRO_CLK); // inf loop here
    if (error != E_NO_ERROR) {
        printf("-->Error initializing UART: %d\n", error);
        printf("HALTED\n");
        LED_On(LED1);
        while (1);
    }


    //## set the real UART pin to 3.3V 
    
    /* works for UART 0 */
    
    mxc_gpio_cfg_t gpioTXD;
    gpioTXD.port = MXC_GPIO1;  // MXC_GPIO0 for UART0; MXC_GPIO1 for UART2 according to datasheet...?  I was using MXC_GPIO1 with UART0 though..
    gpioTXD.mask = MXC_GPIO_PIN_1;
    gpioTXD.pad  = MXC_GPIO_PAD_NONE;
    gpioTXD.func = MXC_GPIO_FUNC_ALT1;
    gpioTXD.vssel= MXC_GPIO_VSSEL_VDDIOH; //voltage on UART pin set to 3.3v, important for iMX board
    MXC_GPIO_Config(&gpioTXD);
    
    mxc_gpio_cfg_t gpioTXD2 = { MXC_GPIO2, MXC_GPIO_PIN_7, MXC_GPIO_FUNC_ALT1, // p2.7 is LPUART TX. P2.6 is LPUART RX.
                                        MXC_GPIO_PAD_NONE, MXC_GPIO_VSSEL_VDDIOH, MXC_GPIO_DRVSTR_0 };
    MXC_GPIO_Config(&gpioTXD2);

    MXC_UART_ClearRXFIFO(MXC_UART_GET_UART(SIG_UART));
    MXC_UART_ClearTXFIFO(MXC_UART_GET_UART(SIG_UART));

    /*
    mxc_uart_req_t uread_req;
    uread_req.uart     = MXC_UART_GET_UART(SIG_UART);
    uread_req.rxData   = uartRxData;
    uread_req.txData   = uartTxData;
    uread_req.rxLen    = BUFF_SIZE;
    uread_req.txLen    = BUFF_SIZE;
    uread_req.callback = readCallback;
    */

    mxc_uart_req_t uwrite_req;
    uwrite_req.uart     = MXC_UART_GET_UART(SIG_UART);
    uwrite_req.txData   = uartTxData;
    uwrite_req.rxData   = uartRxData;
    uwrite_req.txLen    = BUFF_SIZE;
    uwrite_req.rxLen    = 0;
    uwrite_req.callback = NULL;

    READ_FLAG = 1;

    int dma_channel;
    int ret = 0;

    printf("UART Firmware started on UART %i\n", SIG_UART);

}