1. Intro to MicroControllers : Stellaris Launchpad
Class 2:
API Initialization & Use

2. Topics for Today Direct Register Access vs Software Driver Model
System Level vs Device Level
Examples code for relevant devices

3. Direct Register Access
Total Control but more tedious
inc /*
Header files for DRA (inc/lm4fh5qr.h)
*_R files used to access register
*_M used as mask
*_S used to shift

4. Software Driver Model Rapid development Simple Plain English Interface
Slightly less control (sometimes)

5. Example: Set SSI Clock Speed
Direct Register Access (pg 925)
Software Driver Model (pg 336)
SSI0_CR0_R = ((5 << SSI_CR0_SCR_S) | SSI_CR0_SPH |
SSI_CR0_SPO | SSI_CR0_FRF_MOTO | SSI_CR0_DSS_8); OR
SSI0_CR0_R = 0x000005c7;
SSIConfigSetExpClk(SSI0_BASE, , SSI_FRF_MOTO_MODE_3, SSI_MODE_MASTER, ,8);

6. Layout of Program #includes //#defines & Global Variables.
//#defines & Global Variables
//Other Functions (interrupt handlers, subfunctions, etc)
int main(void){
//system level init
//peripheral init
//peripheral use }

7. System Level Init
//Enable Floating Point FPULazyStackingEnable(); //Set the clock speed SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ); IntMasterEnable();

8. Device Init
//Config Enable System Peripheral (Pin Base) Set Pad Config (aka pin mux) Set Direction of Data //Use Read Write

9. Interrupts register handler, then enable, clear flag in interrupt handler
// Interrupt Init IntMasterEnable(); //System Level IntEnable(INT_GPIOA); //Device Level IntPrioritySet(INT_GPIOA, 0x00); //inverse priority // Interrupt functions IntPendClear(INT_GPIOA); //remove pending interrupt from que IntDisable(INT_GPIOA); IntMasterDisable(); You can register / unregister interrupts on the fly, but it does so by loading the NVIC Table into RAM, I would advise against this and make your interrupts static at compile time. The NVIC can be found in the startup_rvmdk.c file in the project root.

10. Devices
GPIO
Timers
Hibernate
I2C
UART
SSI (aka SPI)
ADC

11. GPIO 8 pins per port
//GPIO Init SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA); GPIOPinTypeGPIOOutput(GPIO_PORTA_BASE, GPIO_PIN_1); GPIOPinTypeGPIOInput(GPIO_PORTA_BASE, GPIO_PIN_2); GPIOPinConfigure(); //GPIO Functions GPIOPinWrite(GPIO_PORTA_BASE, GPIO_PIN_1, GPIO_PIN_1); GPIOPinRead(GPIO_PORTA_BASE, GPIO_PIN_1, GPIO_PIN_2);

12. UART
//UART Init #include "utils/uartstdio.c" SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA); GPIOPinConfigure(GPIO_PA0_U0RX); GPIOPinConfigure(GPIO_PA1_U0TX); GPIOPinTypeUART(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1); UARTStdioConfig(0, , SysCtlClockGet()); //UART functions UARTprintf(“text to print”);

13. Timers
//Timer Init TimerConfigure(TIMER0_BASE, TIMER_CFG_PERIODIC); //32bit periodic TimerLoadSet(TIMER0_BASE, TIMER_A, LengthOfTime); //duration for timer TimerEnable(TIMER0_BASE, TIMER_A); //Timer functions usually used as timer interrupts NOTE: LengthOfTime is in system ticks, to calculate real time use this equation Realtime=(1/ClockSpeed)*LengthOfTime

14. Hibernate 32 bit RTC, 15bit sub second timer, battery backed memory
Hibernate is complicated, go look at Page 197 for examples.

15. Analog to Digital Converter (ADC)
// ADC Init ADCSequenceConfigure(ADC0_BASE, 0, ADC_TRIGGER_PROCESSOR, 0); ADCSequenceStepConfigure(ADC0_BASE, 0, 0, ADC_CTL_IE | ADC_CTL_END | ADC_CTL_CH0 ); ADCSequenceEnable(ADC0_BASE, 0); // ADC functions int ulValue; ADCProcessorTrigger(ADC0_BASE, 0); //trigger sample while(!ADCIntStatus(ADC0_BASE, 0, false)){} //wait until sampling complete ADCSequenceDataGet(ADC0_BASE, 0, &ulValue); //get data

16. SSI
// SSI Init SSIConfigSetExpClk(SSI_BASE, SysCtlClockGet(), SSI_FRF_MOTO_MODE0, SSI_MODE_MASTER, , 8); SSIEnable(SSI_BASE); // SSI functions SSIDataGet(SSI_BASE, &data); SSIDataPut(SSI_Base,data);

17. I2C
// Initialize Master and Slave I2CMasterInitExpClk(I2C_MASTER_BASE, SysCtlClockGet(), true); // Specify slave address I2CMasterSlaveAddrSet(I2C_MASTER_BASE, 0x3B, false); // Place the character to be sent in the data register I2CMasterDataPut(I2C_MASTER_BASE, ’Q’); // Initiate send of character from Master to Slave I2CMasterControl(I2C_MASTER_BASE, I2C_MASTER_CMD_SINGLE_SEND); // Delay until transmission completes while(I2CMasterBusBusy(I2C_MASTER_BASE)) { }