LPC844 - SPI sending 2 frames

tyassin1 — Mon, 21 Jun 2021 20:34:48 GMT

Hi,

I try to send 2 frames, each of 8 bits. I want to do this without the SSEL line to go high between frames. It is active low.

I have attached my code below.

Going through the datasheet it seems that I have to change the EOT bit to 0 for the first byte. Then EOT need to be sat to 1 with the transmit of the second byte.

But it does not work. My code just hangs and there is no transmit.

It works fine transmitting 1 frame

Any advice?

Thank you

void spi_setup()
{
SYSCON->SYSAHBCLKCTRL0 |= (1<<11); //Enable clock for SPI0

SWM0->PINASSIGN_DATA[3] &= ~(0xFF<<24);
SWM0->PINASSIGN_DATA[3] |= (25<<24); //Assign SCK to GPIO0_25

SWM0->PINASSIGN_DATA[4] &= ~(0xFF<<0);
SWM0->PINASSIGN_DATA[4] |= (27<<0); //Assign MOSI to GPIO0_27

SWM0->PINASSIGN_DATA[4] &= ~(0xFF<<16);
SWM0->PINASSIGN_DATA[4] |= (26<<16); //Assign SSEL0 to GPIO0_26

SYSCON->FCLKSEL[9] = 1; //Select Main_clk as source for SPI0

SPI0->DLY |= (2<<8); // Frame delay = 2 SPI clock cycles

SPI0->TXCTL = (1 << 20) | // set End Of Transfer
(1 << 21) | // set End Of Frame
(1 << 22) | // RXIGNORE, otherwise SPI hangs until
// we read the data register
((8 - 1) << 24); // 8 bit frames
}

void spi_tx(unsigned char data)
{
// Wait for MSTIDLE, should be a no-op since we are waiting after
// the transfer.
while (!(SPI0->STAT & (1 << 8)));

// Wait for TXRDY
while (!(SPI0->STAT & (1 << 1)));

SPI0->TXDATCTL = (0<<21)|(0<<20)|(data<<0);

// Wait for the transfer to finish
while (!(SPI0->STAT & (1 << 8)));

SPI0->TXDATCTL = (1<<20)|(data<<0);

//SPI0->TXDAT = data;

// Wait for the transfer to finish
while (!(SPI0->STAT & (1 << 8)));

// Force END OF TRANSFER
SPI0->STAT = (1 << 7);

}

Re: LPC844 - SPI sending 2 frames

Alice_Yang — Tue, 22 Jun 2021 09:04:22 GMT

Hello ,

Recommend you refer to the SPI demo under SDK.

And if still can't maintain low, directly use gpio to control slave selection.

Alice

Re: LPC844 - SPI sending 2 frames

tyassin1 — Tue, 20 Jul 2021 20:07:40 GMT

I got it to work without the example code.

Thx

topic LPC844 - SPI sending 2 frames in LPC Microcontrollers

LPC844 - SPI sending 2 frames

Re: LPC844 - SPI sending 2 frames

Re: LPC844 - SPI sending 2 frames