SPI/SSI transmission problems

Marinkovic Aleksandar

Prodigy 75 points

Hello,

I have tried to send data via SPI to a display using TI-RTOS. For initialisation this data is needed to be transmitted:

SS high

4µs delay

1Byte (0x02)

1Byte (0x00)

2µs delay

SS low

40µs delay

DISP high

40µs delay

then the following data

SS is on pin PD1

DISP is on PF1

CLOCK PD0

TX PD3

I have modified the EK_TM4C123GXL.c. I changed the SS to an output.

I've tried the following programm on the tm4c123gxl board. I analysed it with a logic analyser. I hope you can help me out.

And this is what it should look like:

Void SPI_test()

{

GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_1, 0x0);*/

// SS Low

GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_1, 0x00);

// Delay 1ms

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 1000);

Timer_start(timer0);

SPI_Handle handle;

SPI_Params params;

SPI_Transaction spiTransaction;

bool ret;

SPI_Params_init(&params);

params.bitRate = 20000000;

params.mode = SPI_MASTER;

params.dataSize = 8;

params.frameFormat = SPI_POL0_PHA1;

handle = SPI_open(Board_SPI1, &params);

if (handle == NULL) {

System_printf("SPI nicht offen");

}

// Clear Flag

GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_1, 0xFF);

// Delay 4us (mind. 3us)

/*Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 4);

Timer_start(timer0);*/

spiTransaction.count = SPI_MSG_LENGTH;

spiTransaction.txBuf = (Ptr)0b00100000;

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

spiTransaction.count = 8;

spiTransaction.txBuf = (Ptr)0x0;

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

// ^

// |

// Flag Cleared

// Delay 40 us (mind. 30 us)

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 2);

Timer_start(timer0);

// SS Low

GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_1, 0x00);

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 40);

Timer_start(timer0);

// Enable LCD

GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_1, 0xFF);

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 40);

Timer_start(timer0);

// write first line

GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_1, 0xFF);

// Delay 4us (mind. 3us)

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 4);

Timer_start(timer0);

spiTransaction.txBuf = (Ptr)0b11000000;

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

spiTransaction.txBuf = (Ptr)reverseBits(1);

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

int line;

int i;

for(i = 0; i<50; i++)

{

spiTransaction.txBuf = (Ptr)TxMessage[i];

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

}

spiTransaction.txBuf = (Ptr)0x0;

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

//write lines

for(line=2; line<=240; line++)

{

spiTransaction.txBuf = (Ptr)reverseBits(line);

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

for(i = 0; i<50; i++){

spiTransaction.txBuf = (Ptr)TxMessage[i+((line-1)*50)];

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

}

spiTransaction.txBuf = (Ptr)0x0;

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

}

//write last byte

spiTransaction.txBuf = (Ptr)0x0;

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 2);

Timer_start(timer0);

GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_1, 0x00);

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 50000);

Timer_start(timer0);

while(1){

GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_1, 0xFF);

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 4);

Timer_start(timer0);

spiTransaction.txBuf = (Ptr)0x0;

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

spiTransaction.txBuf = (Ptr)0x0;

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 2);

Timer_start(timer0);

GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_1, 0x00);

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 50000);

Timer_start(timer0);

GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_1, 0xFF);

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 40);

Timer_start(timer0);

spiTransaction.txBuf = (Ptr)0b01000000;

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

spiTransaction.txBuf = (Ptr)0x0;

spiTransaction.rxBuf = NULL;

ret = SPI_transfer(handle, &spiTransaction);

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 2);

Timer_start(timer0);

GPIOPinWrite(GPIO_PORTD_BASE, GPIO_PIN_1, 0x00);

Timer_stop(timer0);

Timer_setPeriodMicroSecs(timer0, 50000);

Timer_start(timer0);

}

over 9 years ago

0 Marinkovic Aleksandar over 9 years ago

Prodigy 75 points

Speed is 2MHz, I wrote it false in the programm

0 Marinkovic Aleksandar over 9 years ago

Prodigy 75 points

Excuse me, the first Byte that should be sent is 0x20 instead of 0x02.

0 Moses Isang over 9 years ago in reply to Marinkovic Aleksandar

TI__Expert 8175 points

Hi,
I don't see the problem. From the logic analyzer, I see 0x20 and 0x00 on MOSI which is what you intended. I'm I missing something else?

Regards,
Moses

0 Marinkovic Aleksandar over 9 years ago in reply to Moses Isang

Prodigy 75 points

Hi Moses Isang,

The second picture in my post is how it should look like. I am not able to get this result with my programm.
Here is how it looks like when I try to tramsmit data. This time with correct scaling and frequency.

On this picture you can see that I tried to transmit the bits required for display initialisation via SSI3-module.

0 Moses Isang over 9 years ago in reply to Marinkovic Aleksandar

TI__Expert 8175 points

Hi,

Oh i see. Looking at your SPI transfer code like the chunk below:

spiTransaction.count = SPI_MSG_LENGTH;
spiTransaction.txBuf = (Ptr)0b00100000;
spiTransaction.rxBuf = NULL;
ret = SPI_transfer(handle, &spiTransaction);

I see you're setting the SPI transaction Tx buf to 0b00100000 which is the actual data you want to send unless you have a buffer allocated at the exact address of 0b00100000. The Tx and Rx buffer fields in the transaction structure take pointers to already allocated memory buffers and not the actual data you're trying to send. I was expecting something like:

char buf[1] ;
buf[0] = 0x20; //0b00100000 in Hex

spiTransaction.count = 1; //Number of bytes to be transferred
spiTransaction.txBuf = buf;
spiTransaction.rxBuf = NULL;
ret = SPI_transfer(handle, &spiTransaction);

Let me know if this helps,

Moses

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SPI/SSI transmission problems