topic SPI communication on KL25Z in Kinetis Microcontrollers

SPI communication on KL25Z

michelmeunier — Wed, 30 Dec 2015 13:40:10 GMT

Hello,

I tried to read an ADXL345 accelerometer, I have written my own SPI read and write because it doesn't work with processor expert.

The initialization of SPI is:

--------------------------------------------------

SIM_SCGC5 \|= SIM_SCGC5_PORTD_MASK;	//Turn on clock to D module
SIM_SCGC4 \|= SIM_SCGC4_SPI0_MASK;	//Enable SPI0 clock

PORTD_PCR0 = PORT_PCR_MUX(0x2);	//Set PTD0 to mux 2 [SPI0_PCS0]
PORTD_PCR1 = PORT_PCR_MUX(0x2);	//Set PTD1 to mux 2 [SPI0_SCK]
PORTD_PCR2 = PORT_PCR_MUX(0x2);	//Set PTD2 to mux 2 [SPI0_MOSI]
PORTD_PCR3 = PORT_PCR_MUX(0x2);	//Set PTD3 to mux 2 [SPIO_MISO]

SPI0_C1 = SPI_C1_MSTR_MASK | SPI_C1_SSOE_MASK | SPI_C1_CPHA_MASK | SPI_C1_CPOL_MASK; //Set SPI0 to Master & SS pin to auto SS

SPI0_C2 = SPI_C2_MODFEN_MASK; //Master SS pin acts as slave select output

SPI0_BR = (SPI_BR_SPPR(0x02) \| SPI_BR_SPR(0x08));	//Set baud rate prescale divisor to 3 & set baud rate divisor to 64 for baud rate of 15625 hz
SPI0_C1 \|= SPI_C1_SPE_MASK;	//Enable SPI0

WAIT1_Waitms(500);

------------------------------------------------------------

the read function is quite simple, I write the adress and next read the answer;

-------------------------------------------------------------

uint8_t retour=0,dummy;

bool fini=FALSE;

while(!(SPI_S_SPTEF_MASK & SPI0_S))

{

//While buffer is not empty do nothing

}


SPI0_D =adresse+0x80;	//write adress+0x80 (read mode)

while(!(SPI_S_SPRF_MASK & SPI0_S))

{

//While received buffer is not full do nothing

}

retour=SPI0_D;

return retour;

-------------------------------------------------------

For the test I init the SPI and try to read adress 0x00.

As you can see on the analyzer image, the byte is written, but nothing is read, the KL25Z do nothing. I should have a second set of 8 clock pulses.

Michel

Re: SPI communication on KL25Z

mjbcswitzerland — Wed, 30 Dec 2015 19:25:40 GMT

In order to send an address and then read a further byte you must send two bytes:

- the address

- a 'dummy' one (eg. 0xff) - this will generate the second 8 clocks

- they you will receive the result value back

Regards

Mark

Re: SPI communication on KL25Z

michelmeunier — Wed, 30 Dec 2015 21:28:21 GMT

Thank you Mark, you have solved a part of my problem.

Now the picture of analyzer seems to be correct, but the SPRF bit seems to be unused. I have add a 5ms wait before to read the answer, I should received 0xe5 but I allways get 0!!.

My read function looks like that:

------------------------------

uint8_t retour=0,dummy;

bool fini=FALSE;

while(!(SPI_S_SPTEF_MASK & SPI0_S))

{

//While buffer is not empty do nothing

}

SPI0_D =adresse+0x80;

//write adress+0x80 (read mode)

while(!(SPI_S_SPTEF_MASK & SPI0_S))

{

//While buffer is not empty do nothing

}

SPI0_D =0x00;

//write 0x0 to generate 8 clock pulses

while(!(SPI_S_SPRF_MASK & SPI0_S))

{

//While received buffer is not full do nothing

}

WAIT1_Waitms(5);

retour=SPI0_D;

return retour;

----------------------

And the analyzer:

I think I am that with your help, I am very closed from the solution.

Thanks

Michel

Re: SPI communication on KL25Z

mjbcswitzerland — Wed, 30 Dec 2015 22:15:05 GMT

Michel

After you configure the SPI interface add

(void)SPI0_S;

(void)SPI0_D;

This will ensure that the status flags start to work correctly.

Regards

Mark

Re: SPI communication on KL25Z

kerryzhou — Mon, 04 Jan 2016 08:07:49 GMT

Hi Michel Meunier,

Actually, to KL25Z, you don't need to delay after the SPRF is set, you can read the D register directly, and try again.

If you still not OK, please add the dummy read:

uint8_t retour=0,dummy;

bool fini=FALSE;

while(!(SPI_S_SPTEF_MASK & SPI0_S))

{

//While buffer is not empty do nothing

}

SPI0_D =adresse+0x80;

//write adress+0x80 (read mode)

while(!(SPI_S_SPTEF_MASK & SPI0_S))

{

//While buffer is not empty do nothing

}

dummy = SPI0_S;

SPI0_D =0x00;

//write 0x0 to generate 8 clock pulses

while(!(SPI_S_SPRF_MASK & SPI0_S))

{

//While received buffer is not full do nothing

}

retour=SPI0_D;

return retour;

Wish it helps you!

If you still have question, please let me know!

Have a great day,
Jingjing

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