Tiva Lab 10: Using Ultrasonic Sensor for Distance Determination

Connect the ultrasonic sensor with your Tiva TM4C123G LaunchPad

• Connect the "Trig" pin to GPIO PortF[3]
• Connect the "Echo" pin to Timer1A on PortF[2] with a 200Ω or 220Ω resistor
• Connect the "Vcc" pin to +5V or VBUS on the LaunchPad
• Connect the "Gnd" pin to the GND pin on the LaunchPad

Table 1: Pin Configurations:

Connect the ultrasonic sensor with your Tiva TM4C1294 LaunchPad

• Connect the "Trig" pin to GPIO PortL[5]
• Connect the "Echo" pin to Timer0A on PortL[4] with a 200Ω or 220Ω resistor
• Connect the "Vcc" pin to the +5V pin on the LaunchPad
• Connect the "Gnd" pin to the GND pin on the LaunchPad

Table 1: Pin Configurations:

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdint.h>

#include "TM4C123GH6PM.h"
#include "ez123G.h"
#include "MyDefines.h"

void Setup_UART(void);
void Setup_TIMER(void);
void Setup_GPIO(void);

void        UART0_PrintString(char*);
double      measureT(void);

char str[100];

int main(void)
{
    double      pulseWidth;
    float       distance;
    uint16_t    i = 0;

    Setup_123G_80MHz(); // Setup SystemClock to 80MHz
    Setup_TIMER();      // Setup Timer Input Capture on PORTF[2]
    Setup_UART();       // Setup UART on PA0 and PA1
    Setup_GPIO();       // Setup GPIOs

    sprintf(str,"Project for EE-3450: Ultrasonic Sensor \n\r");
    UART0_PrintString(str);

    while(1){
        // Set "Trig" pin to Low

        timer_waitMillis(500);      // Waiting for 500ms
        // Set "Trig" pin to High for 10ns

        timer_waitMicros(10);       // Waiting for 10ns
        // Set "Trig" pin to Low

        pulseWidth = measureT();    // Call measureT() to get the delta t on the "echo" pin
        // Calculate distance

        sprintf(str,"%d: width: %.2f us, distance: %6.2lf cm \n\r", ++i, pulseWidth * 1000000, distance);
        UART0_PrintString(str);
    }
}
//----------------------------------------------------------------------------------
double measureT(void)
{
    uint32_t highEdge,lowEdge;
    double   deltaT;

    /*Capture firstEgde i.e. rising edge*/
    //1. Clear GPTM Timer A Capture Mode Event by writing 1 to
    //   corresponding bit on GPTMICR (TIMER1->ICR) register

    //2. Waiting for capture rising edge event by check the GPTM Raw Interrupt Status
    //   GPTMRIS (TIMER1->RIS) register

    //3. Set the highEdge from GPTMTAR (TIMER1->TAR) registers

    /*Capture secondEgde i.e. falling edge*/
    //4. Clear GPTM Timer A Capture Mode Event by writing 1 to
    //   corresponding bit on GPTMICR (TIMER1->ICR) register

    //5. Waiting for capture falling edge event by check the GPTM Raw Interrupt Status
    //   GPTMRIS (TIMER1->RIS) register

    //6. Set the lowEdge from GPTMTAR (TIMERa->TAR) registers

    //7. Calculate deltaT = (highEdge - lowEdge) * (1/TimerFreq)
    //   Note: the deltaT must large than zero, cannot be negative value

    return deltaT;
}
//----------------------------------------------------------------------------------
void Setup_UART(void)
{
// Setup UART on 38400bps
#define UARTIBRD 00     // You need to calculate IBRD value
#define UARTFBRD 00     // You need to calculate FBRD value

    // 1. Enable clock to UART Module 0 (SYSCTL_RCGCUART)
    SYSCTL->RCGCUART |= (__);
    // allow time for clock to stabilize
    while((SYSCTL->PRUART & (__)) != (__)){};
    // 2. Disable UART by clearing UARTEN in UARTCTL register
    UART?->CTL &= ~(__);
    // 3. Write BRD to UARTIBRD and UARTFBRD register
    UART?->IBRD = UARTIBRD;
    UART?->FBRD = UARTFBRD;
    // 4. Write UART Line control (UARTLCRH register)
    //    8bit, No parity, 1-stop bit, Enable FIFO
    UART?->LCRH = (__);
    // 5. Configure the UART clock source (UARTCC register)
    UART?->CC = (__);   // Clock Source from System Clock
    // 6. Enable UART by clearing UARTEN in UARTCTL register
    UART?->CTL = (__); // Enable UART0, TXE, RXE
}
//----------------------------------------------------------------------------------
void Setup_TIMER(void)
{
    //* PF2: T1CCP0 (PCTL=07) both edge (edge-time mode)

    // 1 . Enable Clock for TIMER Module
    SYSCTL->RCGCTIMER |= (__);
    while ((SYSCTL->PRTIMER & (__)) != (__)) {}
    // 2. Disable TIMER
    TIMER?->CTL &= ~(__);  // Disable TimerA & TimerB
    // 3. Configure TIMER
    TIMER?->CFG = 0x04;         // Split into two 16-bit timers
    // 4. Configure Timer n Mode: GPTMTAMR
    TIMER?->TAMR = (__);
    // 5. Configure Timer Event Mode: rising-, falling-, or both-edges
    TIMER?->CTL &= ~(__);
    TIMER?->CTL |=  (__);  // Both edges
    // 6. Configure Load
    TIMER?->TAILR = 0xFFFF;
    //Set the prescaler to 0xFF
    TIMER?->TAPR = 0xFF;
    TIMER?->IMR = 0;
    // 7. Enable GPTM Timer
    TIMER?->CTL |= (__);  // Enable TimerB
}
//----------------------------------------------------------------------------------
void Setup_GPIO(void)
{
    // GPIO Initialization and Configuration
    // 1. Enable Clock to the GPIO Modules (SYSCTL->RCGCGPIO |= (_PORTs);)
    SYSCTL->RCGCGPIO |= (__);
    // allow time for clock to stabilize (SYSCTL->PRGPIO)
    while((SYSCTL->PRGPIO & (__)) != (__)){};
    // 2. Unlock PD7 and PF0 on TM4C123G; or PD7 on TM4C1294 (GPIOx->LOCK = 0x4C4F434B; and GPIOx->CR = _PINs;)
    // 3. GPIO Analog Mode Select (GPIOAMSEL)

    // 4. GPIO Port COntrol (GPIOPCTL)

    // 5. Clear AFSEL bits to 0 to select regular I/O

    // 6. GPIO Pin Direction (GPIODIR) 0 for input, 1 for output

    // 7. Set PUR bits to 1 to enable internal pull-up resistor
    // 8. Set DEN bits to 1 to enable data pins

}
//----------------------------------------------------------------------------------
void UART0_PrintString(char * s)
{
    // Code from Lab 09
}

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdint.h>

#include "TM4C1294NCPDT.h"
#include "ez1294.h"
#include "MyDefines.h"

void Setup_UART(void);
void Setup_TIMER(void);
void Setup_GPIO(void);

void UART0_PrintString(char*);
double measureT(void);

char str[100];

int main(void)
{
    double      pulseWidth;
    float       distance;
    uint16_t    i = 0;

    Setup_1294_80MHz(); // Setup SystemClock to 80MHz
    Setup_TIMER();      // Setup Timer Input Capture
    Setup_UART();       // Setup UART on PA0 and PA1
    Setup_GPIO();       // Setup GPIOs

    sprintf(str,"Project for EE-3450: Ultrasonic Sensor \n\r");
    UART0_PrintString(str);

    while(1){
        // Set "Trig" pin to Low

        timer_waitMillis(500);      // Waiting for 500ms
        // Set "Trig" pin to High

        timer_waitMicros(10);       // Waiting for 10ns
        // Set "Trig" pin to Low

        pulseWidth = measureT();    // Call measureT() to get delta t on the "echo" pin
        // Calculate distance

        sprintf(str,"%d: width: %.2f us, distance: %6.2lf cm \n\r", ++i, pulseWidth * 1000000, distance);
        UART0_PrintString(str);
    }
}
//----------------------------------------------------------------------------------
double measureT(void)
{
    uint32_t highEdge,lowEdge;
    double   deltaT;

    /*Capture firstEgde i.e. rising edge*/
    //1. Clear GPTM Timer A Capture Mode Event by writing 1 to
    //   corresponding bit on GPTMICR (TIMER0->ICR) register

    //2. Waiting for capture rising edge event by check the GPTM Raw Interrupt Status
    //   GPTMRIS (TIMER0->RIS) register

    //3. Set the highEdge from GPTMTAR (TIMER0->TAR) registers

    /*Capture secondEgde i.e. falling edge*/
    //4. Clear GPTM Timer A Capture Mode Event by writing 1 to
    //   corresponding bit on GPTMICR (TIMER0->ICR) register

    //5. Waiting for capture falling edge event by check the GPTM Raw Interrupt Status
    //   GPTMRIS (TIMER0->RIS) register

    //6. Set the lowEdge from GPTMTAR (TIMERa->TAR) registers

    //7. Calculate deltaT = (highEdge - lowEdge) * (1/TimerFreq)
    //   Note: the deltaT must large than zero, cannot be negative value

    return deltaT;
}
//----------------------------------------------------------------------------------
void Setup_UART(void)
{
// Setup UART on 38400bps
#define UARTIBRD 00     // You need to calculate IBRD value
#define UARTFBRD 00     // You need to calculate FBRD value

    // 1. Enable clock to UART Module 0 (SYSCTL_RCGCUART)
    SYSCTL->RCGCUART |= (__);
        // allow time for clock to stabilize
    while((SYSCTL->PRUART & (__)) != (__)){};
    // 2. Disable UART by clearing UARTEN in UARTCTL register
    UART?->CTL &= ~(__);
    // 3. Write BRD to UARTIBRD and UARTFBRD register
    UART?->IBRD = UARTIBRD;
    UART?->FBRD = UARTFBRD;
    // 4. Write UART Line control (UARTLCRH register)
    //    8bit, No parity, 1-stop bit, Enable FIFO
    UART?->LCRH = (__);
    // 5. Configure the UART clock source (UARTCC register)
    UART?->CC = (__);   // Clock Source from System Clock
    // 6. Enable UART by clearing UARTEN in UARTCTL register
    UART?->CTL = (__); // Enable UART0, TXE, RXE
}
//----------------------------------------------------------------------------------
void Setup_TIMER(void)
{
    //* PL4: T0CCP0 (PCTL=03) both edge (edge-time mode)

    // 1 . Enable Clock for TIMER Module
    SYSCTL->RCGCTIMER |= (__);
    while ((SYSCTL->PRTIMER & (__)) != (__)) {}
    // 2. Disable TIMER
    TIMER?->CTL &= ~(__);     // Disable Timer
    // 3. Configure TIMER
    TIMER?->CFG = 0x04;         // Split into two 16-bit timers
    // 4. Configure Timer n Mode: GPTMTAMR
    TIMER?->TAMR = (__);
    // 5. Configure Timer Event Mode: rising-, falling-, or both-edges
    TIMER?->CTL &= ~(__);
    TIMER?->CTL |=  (__);     // Both edges
    // 6. Configure Load
    TIMER?->TAILR = 0xffff;
    //Set the prescaler to 0xFF
    TIMER?->TAPR = 0xFF;
    TIMER?->IMR = 0;
    // 7. Enable GPTM Timer
    TIMER?->CTL |= (__);      // Enable Timer
}
//----------------------------------------------------------------------------------
void Setup_GPIO(void)
{
    // GPIO Initialization and Configuration
    // 1. Enable Clock to the GPIO Modules (SYSCTL->RCGCGPIO |= (_PORTs);)
    SYSCTL->RCGCGPIO |= (__);
    // allow time for clock to stabilize (SYSCTL->PRGPIO)
    while((SYSCTL->PRGPIO & (__)) != (__)){};
    // 2. Unlock PD7 and/or PF0 on TM4C123G (GPIOx->LOCK = 0x4C4F434B; and GPIOx->CR = _PINs;)
    // 3. GPIO Analog Mode Select (GPIOAMSEL)

    // 4. GPIO Port COntrol (GPIOPCTL)

    // 5. Clear AFSEL bits to 0 to select regular I/O

    // 6. GPIO Pin Direction (GPIODIR) 0 for input, 1 for output

    // 7. Set PUR bits to 1 to enable internal pull-up resistor
    // 8. Set DEN bits to 1 to enable data pins

}
//----------------------------------------------------------------------------------
void UART0_PrintString(char *s)
{
    // Code from Lab 09
}

SONAR (Sound Navigation and Ranging) uses an ultrasonic signal to determine the presence and distance of objects. The HC-SR04 sensor module includes ultrasonic transmitter, receiver and control circuit. The ultrasonic transmitter emits 40 kHz sound pulses, and the receiver receives the return echo signal. The idea behind distance estimation is that objects reflect sound and that the time between emitting a sound pulse and receiving an echo can be translated into distance given the speed of sound through air.

The HC-SR04 sensor documentation provides a detailed description of how it operates, but a few points are worth emphasizing here:

• The HC-SR04 sensor uses two signal pins, one is for trigger and another is for receiving echo signal. The "trigger" pin is connected to the output pin of GPIO, and the "echo" pin is attached to the Input Capture pin of Timer with a 200Ω (or 220Ω) resistor to protect the Tiva LaunchPad.
• The HC-SR04 sensor must be "triggered" in order to enable pulsing. Therefore, you need to set the GPIO output pin high and then low. The sensor documentation discusses how long the trigger pulse should be.
• The echo signal received from the sensor will rise and then fall on the "echo" pin. The distance between these two edges is directly proportional to the round-trip distance between the sensor and the object. Input capture when properly configured to Edge-Time mode will identify the edges of the signal and set TIMERn_TAR_R to the current counter value when the events/edges are detected. The difference in counter values represents the signal's pulse width as time. The actual amount of time can be determined when the system clock frequency is used to compute the amount of time each counter value represents.
• After you calculate the value, send the distance in centimeters (cm) to your PC through UART.

Add a PWM function to the system, and connect a motor to the PWM signal through a motor driver. Control the motor speed according to the following conditions:

• If there is no object in the front of the fan, or if the distance between the fan and the object is more than 20 cm, then turn the fan speed to 100%.
• If any object is close to the fan within 20 cm ~ 10 cm, adjust the fan speed to 50%.
• Stop the fan when the object is within 10 cm.