MK26 SPI2 data transfer issues

pascalschröer — Fri, 08 Apr 2016 17:29:44 GMT

Hi to all,

I try to send a few bytes (up to 4) via SPI interface to an external flash. I have already worked with Kinetis' SPI interface without any troubles. Right now, I'm working with a Kinetis MK26 device. The problem is:

I'm not able to send more than 2 bytes in a row (without a CS toggle). The transfer is interrupted after 2 Bytes, irrespective of what I'm doing!

0. General instructions:

All port, clock and NVIC configurations are finished and work!

1. Initialisation:

void SPI2_init(void) {

/* Enable SPI2 interface master mode and set CS0 inactive high */

SPI2_MCR = 0x00

| SPI_MCR_MSTR_MASK

| SPI_MCR_PCSIS(0x01);

/* Set baud rate / frame size is 8 bit for CS 0 */

SPI2_CTAR0 = 0x00

| SPI_CTAR_FMSZ(0x07)

| SPI_CTAR_BR(0x06);

/* Enable end of queue interrupt */

SPI2_RSER |= SPI_RSER_EOQF_RE_MASK;

}

2. Send data:

void SPI2_send(void) {

/* Clear transmit FIFO full flag */

SPI2_SR |= SPI_SR_TFFF_MASK;

/* Wait for FIFO space */

while(!(SPI2_SR & SPI_SR_TFFF_MASK));

/* Send first 8 bytes and DON'T let the CS0 go back to inactive state! */

SPI2_PUSHR = 0x00

| SPI_PUSHR_TXDATA(0x33)

| SPI_PUSHR_PCS(1)

| SPI_PUSHR_CTAS(0)

| SPI_PUSHR_CONT_MASK;

/* Send second 8 bytes and DON'T let the CS0 go back to inactive state! */

SPI2_PUSHR = 0x00

| SPI_PUSHR_TXDATA(0x66)

| SPI_PUSHR_PCS(1) //CS0

| SPI_PUSHR_CTAS(0)

| SPI_PUSHR_CONT_MASK;

/* Send last 8 bytes and LET the CS0 go back to inactive state! */

SPI2_PUSHR = 0x00

| SPI_PUSHR_TXDATA(0x99)

| SPI_PUSHR_PCS(1) //CS0

| SPI_PUSHR_CTAS(0)

| SPI_PUSHR_EOQ_MASK; //generate end of queue interrupt

}

3. Receive / interpret data:

void SPI2_isr(void) {

/* dummy variable */

uint32_t tmp = 0;

/* Get the SPI FIFO values */

tmp |= SPI2_POPR << 14;

tmp |= SPI2_POPR << 6;

tmp |= SPI2_POPR >> 2;

/* Clear receive and transmit FIFO */

SPI2_MCR |= SPI_MCR_CLR_RXF_MASK;

SPI2_MCR |= SPI_MCR_CLR_TXF_MASK;

/* Clear end of queue flag! */

SPI2_SR |= SPI_SR_EOQF_MASK;

}

4. Function call:

void main(void) {

... //Init all the rest

/* Init SPI2 interface */

SPI2_init();

for(;;) {

delay_ms(10);

SPI2_send();

}

5. Result:

The result is, that I just transfer the first two bytes! Btw. I mentioned, that the SPI2_isr() is called twice after the function call of SPI2_send()...

Thanks for your help!

Pascal

Re: MK26 SPI2 data transfer issues

xiangjun_rong — Mon, 11 Apr 2016 06:27:22 GMT

Hi, Pascal,

Frankly speaking, I am not clear about your question, do you mean that the SPI just transfers two bytes even if you write 4 bytes? I suspect that the FIFO save the bytes but not send out.

I suggest you disable FIFO mode by setting the DIS_TXF and DIS_RXF bits in SPIx_MCR, and suggest you set the TCF_RE to enable interrupt when the byte has been transferred.

Hope it can help you.

XiangJun Rong

Re: MK26 SPI2 data transfer issues

pascalschröer — Fri, 15 Apr 2016 06:55:19 GMT

Hi xiangjun,

thanks for your answer! You are completely right with your suggestion of the fault. I just transfer two bytes even if I write 4 bytes. The solution is to DISABLE the FIFO by setting DIS_TXF and DIS_RXF. To generate the interrupt I use the TCIF.

Thanks!

Pascal

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MK26 SPI2 data transfer issues

Re: MK26 SPI2 data transfer issues

Re: MK26 SPI2 data transfer issues