SSI (SPI) interface on TM4C123GXL

Amit Ashara said:

First of all the DRM is especially not a good manner to program the device.

So true - fully agree - yet we wonder, "How did poster make this choice?"   Did poster even know that a powerful code library exists?

We've long noted that DRM (Direct Register Macros) are the (predominant) code examples w/in the otherwise detailed MCU Manuals.   In fact - the MCU Manuals - unless they've changed recently - give no hint that StellarisWare or TivaWare even exist!   That seems a glaring oversight - does it not - and may explain why "too many" posters present here - using strictly DRM!

Multiple mentions of the extensive driver library - w/in the MCU Manuals - may reduce the (much harder) use of DRM by posters who are unaware of the extensive code libraries...   (this reporter has past appealed for such "code library mention" - to the (usual) vendor silence...)

Thanks Amit for your answer.


I'm a newbie using this microcontroller so i thought i was a great idea try to program something using registers directly to understand the architecture of the microcontroller and adquaire some experience. Until now I had never programmed an arm.  Thank you for your advice about the example. I'll try to follow it.


Thanks.

Hi Amit.

Following your advice i downloaded Tiva libraries and examples and i tried to program the SSI2 of my TM4C123GH6PMI following the example. My code is pasted below.
 I'm still having the same problems... I recieve nothing but 0x00. I've done different test. Sometimes using interruptions and other times not using it. Using tiva the interruption Rx flag is not set despite is enable RX interruption in the SSIIM register and the global interruptions are enable. On the other hand when I use the blocking RX commad of TIva to receive the data i previusly send I only get 0x00.

void Init_SSI2(){
    SysCtlPeripheralEnable(SYSCTL_PERIPH_SSI2);

    // For this example SSI2 is used with PortB[4:7]. clock, fss, rx, tx
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);
    GPIOPinConfigure(GPIO_PB4_SSI2CLK); 
    GPIOPinConfigure(GPIO_PB5_SSI2FSS);
    GPIOPinConfigure(GPIO_PB6_SSI2RX);
    GPIOPinConfigure(GPIO_PB7_SSI2TX);  
    GPIOPinTypeSSI(GPIO_PORTB_BASE, GPIO_PIN_7 | GPIO_PIN_6 | GPIO_PIN_5 | GPIO_PIN_4); //tx, rx, fss, clock
      
    SSIConfigSetExpClk(SSI2_BASE, SysCtlClockGet(), SSI_FRF_MOTO_MODE_3, SSI_MODE_MASTER, 1000000, 3);
        
     //!!!!!!!
     SSI2_CR1_R |= 0x01;  // I set the  loopback operation mode manually


    SSIEnable(SSI2_BASE);    // Enable the SSI0 module.
        
     // Read any residual data from the SSI port.
    while(SSIDataGetNonBlocking(SSI2_BASE, &buffSSIRx[0]))    {  }      
}

//SEND function
void UART0Enviar(const unsigned char *pbuff, short numdatos){ // Send a string to the UART.
    while(numdatos--){   // Loop while there are more characters to send.
            letra=    *pbuff;
      ROM_UARTCharPutNonBlocking(UART0_BASE, *pbuff++);        // Write the next character to the UART.
    }
}}

//RECEIVE function. i've been using different options.
void SSI2recibir(){
    unsigned long data;
    while((SSI2_SR_R & 0x04)==0x04 ){  //fifo rx not empty RNE
        if((SSI2_SR_R & 0x10) ==0x00){         //no busy BSY
            data=    SSI2_DR_R;            
            OuttoUART0( data,"SSI2_DR_R ")
        }
    }
}

Any idea???

I wrote it to:  unsigned short data; while there are data in the Rx FIFO and SSI2 is not busy. But I always get 0x00.

Have any idea which is the problem?