LPCXpresso IDEのトピックRe: SPI debugging

SPI debugging

lpcware — Wed, 15 Jun 2016 22:19:52 GMT

Content originally posted in LPCWare by drat on Wed Aug 24 19:36:53 MST 2011
Hi,

I am developing SPI on the LPC17xx and I was wondering if the SSEL needs to be controlled by me or will the hardware do that?

the setup code is as follows:

SCB_PCLKSEL0 |= (1<<16);//PERIPHERAL CLOCK SELECTION FOR SPI
PCB_PINSEL0 |= (3<<30); //select SCK on pin P0.15
PCB_PINSEL1 |= 0b111111; //select SSEL -> P0.16 and MISO -> P0.17 and MOSI -> P0.18
S0SPCCR |= 8;//CLOCK DEVIDER
S0SPCR |= (1<<3);//CPHA = 1; DATA IS SAMPLED ON THE SECOND CLOCK EDGE OF SCK
S0SPCR |= (1<<4);//CPOL = 1; CLOCK POLARITY; ACTIVE LOW
S0SPCR |= (1<<5);//MSTR = 1; MASTER MODE;

can anybody help me understand why SPI does not work?

Re: SPI debugging

lpcware — Wed, 15 Jun 2016 22:19:53 GMT

Content originally posted in LPCWare by Ex-Zero on Wed Aug 24 19:55:50 MST 2011
There's an SSP sample in examples in NXP_LPCXpresso1769_MCB1700_2011-02-11.zip.

It's SSP0Init could help you:

void SSP0Init( void )
{
  uint8_t i, Dummy=Dummy;

  /* Enable AHB clock to the SSP0. */
  LPC_SC->PCONP |= (0x1<<21);

  /* Further divider is needed on SSP0 clock. Using default divided by 4 */
  LPC_SC->PCLKSEL1 &= ~(0x3<<10);

  /* P0.15~0.18 as SSP0 */
  LPC_PINCON->PINSEL0 &= ~(0x3UL<<30);
  LPC_PINCON->PINSEL0 |= (0x2UL<<30);
  LPC_PINCON->PINSEL1 &= ~((0x3<<0)|(0x3<<2)|(0x3<<4));
  LPC_PINCON->PINSEL1 |= ((0x2<<0)|(0x2<<2)|(0x2<<4));
  
#if !USE_CS
  LPC_PINCON->PINSEL1 &= ~(0x3<<0);
  LPC_GPIO0->FIODIR |= (0x1<<16);        /* P0.16 defined as GPIO and Outputs */
#endif
        
  /* Set DSS data to 8-bit, Frame format SPI, CPOL = 0, CPHA = 0, and SCR is 15 */
  LPC_SSP0->CR0 = 0x0707;

  /* SSPCPSR clock prescale register, master mode, minimum divisor is 0x02 */
  LPC_SSP0->CPSR = 0x2;

  for ( i = 0; i < FIFOSIZE; i++ )
  {
    Dummy = LPC_SSP0->DR;        /* clear the RxFIFO */
  }

  /* Enable the SSP Interrupt */
  NVIC_EnableIRQ(SSP0_IRQn);
    
  /* Device select as master, SSP Enabled */
#if LOOPBACK_MODE
  LPC_SSP0->CR1 = SSPCR1_LBM | SSPCR1_SSE;
#else
#if SSP_SLAVE
  /* Slave mode */
  if ( LPC_SSP0->CR1 & SSPCR1_SSE )
  {
    /* The slave bit can't be set until SSE bit is zero. */
    LPC_SSP0->CR1 &= ~SSPCR1_SSE;
  }
  LPC_SSP0->CR1 = SSPCR1_MS;        /* Enable slave bit first */
  LPC_SSP0->CR1 |= SSPCR1_SSE;    /* Enable SSP */
#else
  /* Master mode */
  LPC_SSP0->CR1 = SSPCR1_SSE;
#endif
#endif
  /* Set SSPINMS registers to enable interrupts */
  /* enable all error related interrupts */
  LPC_SSP0->IMSC = SSPIMSC_RORIM | SSPIMSC_RTIM;
  return;
}

Quote:

...SSEL needs to be controlled by me or will the hardware do that?

As shown in this sample you can control CS yourself (with GPIO) or let the hardware do that

Re: SPI debugging

lpcware — Wed, 15 Jun 2016 22:19:54 GMT

Content originally posted in LPCWare by Rob65 on Thu Aug 25 00:25:58 MST 2011
Drat,

SSEL can be controlled by the SSP module but then it works as stated in the user manual. Then for each and every frame (byte/word) that you send, the SSEL becomes active and inactive in between.

Why? Cause this is the 'SPI standard' although I don't know why because the SPI devices I know all have a 'chip select' that is active during a whole transaction of multiple words.

So for most of your application you are free to use any GPIO pin as SSEL/CS since that is how you want to use it.

Regards,
[INDENT]Rob
[/INDENT]

Re: SPI debugging

lpcware — Wed, 15 Jun 2016 22:19:54 GMT

Content originally posted in LPCWare by drat on Thu Aug 25 13:37:20 MST 2011
Thanks Zero and rob.

My problem is when i scope the pins i do not see a clock signal or a data out signal.

the pins are configured to having internal pull ups and i was wondering if i have set up some thing wrong. also I have changed the P0.16 from being hardware controlled to being controlled by me i.e it is in gpio configuration. when i scope p0.16 i can see it jump up and down but the other pins seem like they are dead.

any thoughts?

Re: SPI debugging

lpcware — Wed, 15 Jun 2016 22:19:55 GMT

Content originally posted in LPCWare by Ex-Zero on Thu Aug 25 14:09:16 MST 2011

Quote: drat
My problem is when i scope the pins i do not see a clock signal or a data out signal

#1 Are you aware that SPI means shifting bits from MOSI to slave and back to MISO ? Without writing data to your SPI data register you will see nothing :eek:

#2 Perhaps it's a good idea to use SSP instead of SPI (see sample above).

#3 Also it could be a good idea to zip and post your project :)

#4 Did you check PCSPI bit in PCONP ?

Re: SPI debugging

lpcware — Wed, 15 Jun 2016 22:19:55 GMT

Content originally posted in LPCWare by NXP_Europe on Thu Aug 25 14:48:03 MST 2011
Hello drat,

For some general info about the SPI-bus

see ...
http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus

Re: SPI debugging

lpcware — Wed, 15 Jun 2016 22:19:56 GMT

Content originally posted in LPCWare by drat on Thu Aug 25 19:20:53 MST 2011
Thanks everybody for your kind help!

I realized that the SPI line was running faster than I thought and therefore I was not scoping it right. :o

yet again thanks for all your help guys!