Hard Fault trying to access LPUART0->STAT

[robertpoor]

I recently broke the serial I/O routines in my KL27Z :smileysilly:: I'm now getting hard faults when I first try to access the LPUART0->STAT register in the LPUART_GetStatusFlags(base) method, specifically:

temp = base->STAT;

... where base = LPUART0 = 0x40054000.  

Any hints on what I might have failed to initialize?

Prior to calling LPUART_GetStatusFlags(base), I've done the following:

  // from BOARD_InitPins()
  CLOCK_EnableClock(kCLOCK_PortA);                           /* Port A Clock Gate Control: Clock enabled */
  PORT_SetPinMux(PORTA, PIN1_IDX, kPORT_MuxAlt2);            /* PORTA1 (pin 23) is configured as LPUART0_RX */
  PORT_SetPinMux(PORTA, PIN2_IDX, kPORT_MuxAlt2);            /* PORTA2 (pin 24) is configured as LPUART0_TX */
  SIM->SOPT5 = ((SIM->SOPT5 &
    (~(SIM_SOPT5_LPUART0TXSRC_MASK | SIM_SOPT5_LPUART0RXSRC_MASK))) /* Mask bits to zero which are setting */
      | SIM_SOPT5_LPUART0TXSRC(SOPT5_LPUART0TXSRC_LPUART_TX) /* LPUART0 Transmit Data Source Select: LPUART0_TX pin */
      | SIM_SOPT5_LPUART0RXSRC(SOPT5_LPUART0RXSRC_LPUART_RX) /* LPUART0 Receive Data Source Select: LPUART_RX pin */
    );
  // Serial initialization
  CLOCK_SetLpuart0Clock(0x03);  // MCGIRCLK (correct?)
  lpuart_config_t config;
  LPUART_GetDefaultConfig(&config);
  config.baudRate_Bps = baud_rate;
  config.enableTx = true;
  config.enableRx = true;
  LPUART_Init(LPUART0, &config, CLOCK_GetFreq(kCLOCK_McgInternalRefClk));

  // ### It gets a hard fault inside the call to LPUART_GetStatusFlags ###
  while (!(kLPUART_TxDataRegEmptyFlag & LPUART_GetStatusFlags(LPUART0))) {
    // busy wait for previous tx data...
  }
  // ... doesn't get here...
  LPUART_WriteByte(LPUART0, ch);

[robertpoor]

Solved my problem.  It was in the call to CLOCK_GetFreq(...) -- I was passing kCLOCK_McgIrc48MClk (despite what I showed in my code above) rather than kCLOCK_McgInternalRefClk for VLPR mode and kCLOCK_McgPeriphClk for RUN mode.

[mjbcswitzerland]

Hi

Check that the LPUART is enabled/clocked in SIM_SCGC5 before accessing any of its registers.

#define SIM_SCGC5_LPUART0        0x00100000

Regards

Mark

[robertpoor]

Mark: That's a good start -- thanks!  I'm looking over the LPUART interrupt example:

<sdk>/boards/frdmkl27z/driver_examples/lpuart/interrupt/

... and trying to figure out where SIM_SCGC5 is getting set there.  What's the name of the method there that's setting SIM_SCGC5?  Thanks in advance (in the meantime I'll keep digging...).

[mjbcswitzerland]

Robert

I don't know what method is used in the example.
I use (in the uTasker project)
POWER_UP(5, SIM_SCGC5_LPUART0);                              // power up LPUART 0
which equates to
SIM_SCGC5 |= SIM_SCGC5_LPUART0;

and ultimately to

*(volatile unsigned long*)(0x40048038) |= 0x00100000;

Regards

Mark

[robertpoor]

Fair enough - thanks.  I believe part of my problem is that I'm running in VLPR mode (rather than RUN mode) and I need to adjust clock sources accordingly.  I'll keep digging.

[Hui_Ma]

Hi Robert,

The KSDK software is using below function to enable the LPUART0 module clock at SIM_SCGC5 register:

/*!
 * @brief Enable the clock for specific IP.
 *
 * @param name  Which clock to enable, see \ref clock_ip_name_t.
 */
static inline void CLOCK_EnableClock(clock_ip_name_t name)
{
    uint32_t regAddr = SIM_BASE + CLK_GATE_ABSTRACT_REG_OFFSET((uint32_t)name);
    (*(volatile uint32_t *)regAddr) |= (1U << CLK_GATE_ABSTRACT_BITS_SHIFT((uint32_t)name));
}

Please add below code to your application before any LPUART0 register access:

CLOCK_EnableClock(kCLOCK_Lpuart0);

Wish it helps.

Have a great day,
Ma Hui

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