Hard fault writing LPSPI0->TDR

[nobodyKnows]

Hello,

I try to write a function for a very small bootloader. Which should send commands to a display.

However the last statement "LPSPI0->TDR = (uint32_t)(0x20<<8);" cause a hard fault and I dont know why. Can anyone help me? The MCU is a K32L2A31A.

__attribute__ ((naked, section(".after_vectors.reset")))
void showBLMInfo(void){

	//Connect CMP1 with TPM2
	TRGMUX_TPM2 = TRGMUX_TRGCFG_SEL0(0b100111);

	//Comparator for regulated Chargepump
	PCC_CMP1 = PCC_CLKCFG_CGC_MASK; //Clock enable
	//Caution Vin2 as reference is VDD, datasheet is wrong here!
	CMP1->DACCR = CMP_DACCR_DACEN_MASK | CMP_DACCR_VRSEL_MASK | CMP_DACCR_VOSEL(0x2E);
	CMP1->MUXCR = CMP_MUXCR_MSEL(7) | CMP_MUXCR_PSEL(0);
	CMP1->CR1 = CMP_CR1_EN_MASK;

	//Generate PWM for Chargepump
	PCC_TPM2 = PCC_CLKCFG_CGC_MASK | PCC_CLKCFG_PCS(2); //Clock enable, Fast IRC
	TPM2->CONF = TPM_CONF_CPOT_MASK | TPM_CONF_TRGSEL(0) | TPM_CONF_DBGMODE_MASK;
	TPM2->CNT = 0;
	TPM2->MOD = 10;
	TPM2->CONTROLS[1].CnSC = TPM_CnSC_ELSB_MASK  | TPM_CnSC_MSB_MASK;
	TPM2->CONTROLS[1].CnV = 5;

	//Enable Chargepump
	TPM2->SC = TPM_SC_CMOD(1) | TPM_SC_PS(2);

	//GPIO
	//GPIO_SPI0_CS_DISP_GPIO->PCOR = GPIO_SPI0_CS_DISP_GPIO_PIN_MASK;
	//EN_U_BAT, EN_DISP
	PCC_PORTE = PCC_CLKCFG_CGC_MASK; //Clock enable PORT E
	PCC_PORTD = PCC_CLKCFG_CGC_MASK; //Clock enable PORT D
	PORTE->PCR[1] = PORT_PCR_MUX(1); //EN_U_BAT
	PORTE->PCR[25] = PORT_PCR_MUX(2); //EN_DISP
	PORTD->PCR[0] = PORT_PCR_MUX(2); //CS
	PORTD->PCR[1] = PORT_PCR_MUX(2); //SCK
	PORTD->PCR[2] = PORT_PCR_MUX(2); //MOSI
	GPIOE->PDDR = (1U << 25U) | (1U << 1U);
	GPIOE->PSOR = (1U << 25U) | (1U << 1U);

	//1Hz Refresh Clock
	//RTC->CR |= RTC_CR_CPE(1);
	PCC_LPSPI0 = PCC_CLKCFG_CGC_MASK | PCC_CLKCFG_PCS(2); //Clock enable

	LPSPI0->CR = LPSPI_CR_DBGEN_MASK | LPSPI_CR_MEN_MASK;
	LPSPI0->CFGR1 = LPSPI_CFGR1_MASTER_MASK | LPSPI_CFGR1_PCSPOL(1) | LPSPI_CFGR1_AUTOPCS_MASK;
	LPSPI0->CCR = LPSPI_CCR_PCSSCK(11)|LPSPI_CCR_SCKPCS(2)|LPSPI_CCR_DBT(4);

	//Send Display clear command
	LPSPI0->TCR = LPSPI_TCR_FRAMESZ(15) | LPSPI_TCR_PRESCALE(4) | LPSPI_TCR_TXMSK_MASK | LPSPI_TCR_CONT_MASK; //16bit Transfer
	LPSPI0->TDR = (uint32_t)(0x20<<8);
}

 Thanks a lot in advance.

[bobpaddock · Accepted solution]

Unless the function is an interrupt it should not be declared as naked.

[nobodyKnows]

Hello,

thanks a lot this was the solution. Just leave naked

Best regards

[nobodyKnows]

Hello,

I found out the issue is not writing to "LPSPI0->TDR". The issue is the return of the function. Why a return from a function cause a hard fault in startup code? The call stack looks good before the hardfault cause. 

I hope someone knows what is going on here.

Thanks a lot and best regards