Tiva Lab 06: Stepper Motor Interface

Pin Configurations

Pin Configurations

GPIO Initialization Configuration

Next, we need to configure all the GPIO ports and pins that are used in the design.

According to the pin connections, complete the following GPIO configurations for each port. Fills the pin field by the value below:

• 0: Clean the bit
• 1: Set the bit
• x: Do not change the bit
• d: Do not care

For both TM4C123GXL and TM4C1294XL LaunchPads, the Port C [3:0] are used for JTAG/SWD. Therefore, when you configure Port C, you have to use bitwise operators to make sure your new configuration settings do not affect the JTAG/SWD function (PC3 ~ PC0).

Most of GPIO pins are configured as GPIOs and tri-stated by default (GPIOPCTL = 0, CPIOAFSEL = 0, GPIODIR = 0, GPIOPUR = 0, GPIOPDR = 0, GPIOODR = 0)

1. Enable Clock to the GPIO Modules (RCGCGPIO register)
   TM4C123G: SYSCTL->RCGCGPIO |= (_PORTs); |= binary = hex
   

   8	4	2	1		8	4	2	1
   7	6	5	4		3	2	1	0	bit
   		Port F	Port E		Port D	Port C	Port B	Port A	port
   0	0			-

   
   TM4C1294: SYSCTL->RCGCGPIO |= (_PORTs); |= binary = hex
   

   8	4	2	1		8	4	2	1		8	4	2	1		8	4	2	1
   15	14	13	12		11	10	9	8		7	6	5	4		3	2	1	0	bit
   	Port Q	Port P	Port N		Port M	Port L	Port K	Port J		Port H	Port G	Port F	Port E		Port D	Port C	Port B	Port A	port
   0				-					-					-

   After enabling the clock signal, check the PRGPIO register until the corresponding bit is set to 1.
   
   In Assembly:
   

               LDR     R0, =SYSCTL_PRGPIO_R
   Wait4GPIO   LDR     R1, [R0]
               TST     R1, #(__)
               BEQ     Wait4GPIO

   In c:
   

   while ( (SYSCTL->PRGPIO & ____ ) != ____ ) {};

2. Unlock Port
   TM4C123G: PD7 and PF0 are locked after reset.
   TM4C1294: PD7 and PE7 are locked after reset
   If those pins are used in the design, they must be unlocked first. To unlock the port, 0x4C4F434B must be written into the GPIOLOCK register and uncommit it by setting the GPIOCR register.
   

   		8	4	2	1		8	4	2	1
   		7	6	5	4		3	2	1	0	bit
   Port		Pin 7	Pin 6	Pin 5	Pin 4	-	Pin 3	Pin 2	Pin 1	Pin 0	pin	Value in Hex		Register		Value to Register
   -						-					=		➤	GPIO ->LOCK	=	0x4C4F434B
   	-					-					=		➤	GPIO ->CR
   -						-					=		➤	GPIO ->LOCK	=	0x4C4F434B
   	-					-					=		➤	GPIO ->CR

Convert above configuration into registers

3. GPIO Analog Mode Select
   If any pin is used as an Analog signal (check Signal Type field on table 1), the appropriate bit in AMSEL must be set.
   
   • 0: Digital signal
   • 1: Analog signal

   		8	4	2	1		8	4	2	1
   		7	6	5	4		3	2	1	0	bit
   Port		Pin 7	Pin 6	Pin 5	Pin 4	-	Pin 3	Pin 2	Pin 1	Pin 0	pin	Value in Hex		Register		Value to Register
   	-					-					=		➤	GPIO ->AMSEL
   	-					-					=		➤	GPIO ->AMSEL
   	-					-					=		➤	GPIO ->AMSEL
   	-					-					=		➤	GPIO ->AMSEL
   	-					-					=		➤	GPIO ->AMSEL
   	-					-					=		➤	GPIO ->AMSEL
   	-					-					=		➤	GPIO ->AMSEL

4. GPIO Port Control (PCTL)
   The PCTL register is used to select the specific peripheral signal for each GPIO pin when using the alternate function mode.
   
   • 0: GPIO
   • 1~0xF: Check the GPIO Pins and Alternate Function table
   Check the PMCn bit field in the PCTL register from "Lesson 02: Verilog HDL".
   

   8421

   8421

   8421

   8421

   8421

   8421

   8421

   8421

   31~28

   27~24

   23~20

   19~16

   15~12

   11~8

   7~4

   3~0

   bit

   Port

   Pin 7

   Pin 6

   Pin 5

   Pin 4

   -

   Pin 3

   Pin 2

   Pin 1

   Pin 0

   pin

   Value in Hex

   Register

   Value to Register

   -

   -

   =

   ➤

   GPIO ->PCTL

   -

   -

   =

   ➤

   GPIO ->PCTL

   -

   -

   =

   ➤

   GPIO ->PCTL

   -

   -

   =

   ➤

   GPIO ->PCTL

   -

   -

   =

   ➤

   GPIO ->PCTL

   -

   -

   =

   ➤

   GPIO ->PCTL

   -

   -

   =

   ➤

   GPIO ->PCTL

5. GPIO Alternate Function Select (AFSEL)
   Setting a bit in the AFSEL register configures the corresponding GPIO pin to be controlled by PCTL peripheral function.
   
   • 0: General I/O
   • 1: Pin connected to the digital function defined in the PCTL register
   
   

   		8	4	2	1		8	4	2	1
   		7	6	5	4		3	2	1	0	bit
   Port		Pin 7	Pin 6	Pin 5	Pin 4	-	Pin 3	Pin 2	Pin 1	Pin 0	pin	Value in Hex		Register		Value to Register
   	-					-					=		➤	GPIO ->AFSEL
   	-					-					=		➤	GPIO ->AFSEL
   	-					-					=		➤	GPIO ->AFSEL
   	-					-					=		➤	GPIO ->AFSEL
   	-					-					=		➤	GPIO ->AFSEL
   	-					-					=		➤	GPIO ->AFSEL
   	-					-					=		➤	GPIO ->AFSEL

6. GPIO Pin Direction (DIR)
   Set pin direction
   
   • 0: Input pin
   • 1: Output pin
   
   

   		8	4	2	1		8	4	2	1
   		7	6	5	4		3	2	1	0	bit
   Port		Pin 7	Pin 6	Pin 5	Pin 4	-	Pin 3	Pin 2	Pin 1	Pin 0	pin	Value in Hex		Register		Value to Register
   	-					-					=		➤	GPIO ->DIR
   	-					-					=		➤	GPIO ->DIR
   	-					-					=		➤	GPIO ->DIR
   	-					-					=		➤	GPIO ->DIR
   	-					-					=		➤	GPIO ->DIR
   	-					-					=		➤	GPIO ->DIR
   	-					-					=		➤	GPIO ->DIR

7. Internal Pull-Up Resistor (PUR), Pull-Down Resistor (PDR), and Open-Drain (ODR)
   PUR: The pull-up control register
   PDR: The pull-down control register
   ODR: The open-drain control register
   
   • 0: Disable
   • 1: Enable
   
   

   		8	4	2	1		8	4	2	1
   		7	6	5	4		3	2	1	0	bit
   Port		Pin 7	Pin 6	Pin 5	Pin 4	-	Pin 3	Pin 2	Pin 1	Pin 0	pin	Value in Hex		Register		Value to Register
   	-					-					=		➤	GPIO ->
   	-					-					=		➤	GPIO ->
   	-					-					=		➤	GPIO ->
   	-					-					=		➤	GPIO ->
   	-					-					=		➤	GPIO ->
   	-					-					=		➤	GPIO ->
   	-					-					=		➤	GPIO ->

8. GPIO Digital Enable
   Enables all the pins that are used in the design, including GPIO pins and alternate function pins.
   
   • 0: Pin undriven
   • 1: Enable pin
   
   

   		8	4	2	1		8	4	2	1
   		7	6	5	4		3	2	1	0	bit
   Port		Pin 7	Pin 6	Pin 5	Pin 4	-	Pin 3	Pin 2	Pin 1	Pin 0	pin	Value in Hex		Register		Value to Register
   	-					-					=		➤	GPIO ->DEN
   	-					-					=		➤	GPIO ->DEN
   	-					-					=		➤	GPIO ->DEN
   	-					-					=		➤	GPIO ->DEN
   	-					-					=		➤	GPIO ->DEN
   	-					-					=		➤	GPIO ->DEN
   	-					-					=		➤	GPIO ->DEN

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

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

void Setup_GPIO(void);

#define CW    0
#define CCW   1
void StepperMotor(int s, bool direction);
volatile uint32_t *Stepper = (uint32_t *)GPIO? + (_PIN? | .... );

//------------------------------------------------------------------------------
int main()
{
    int i = 0;

    Setup_GPIO();
    *Stepper = ____; // Step 0 value

    while(1){
        // If users press SW1, rotate CW for 5 steps

		// If users press SW2, rotate CCW for 5 steps

        DelayMs(200);
    }
}
//------------------------------------------------------------------------------
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 GPIO only PD7, PF0 on TM4C123G; PD7, PE7 on TM4C1294 (GPIOx->LOCK = 0x4C4F434B; and GPIOx->CR = _PINs;)
    GPIOF->LOCK = 0x4C4F434B;   // Unlock for GPIOF
    GPIOF->CR |= _PIN0;         // Commit for PIN0
    GPIOF->LOCK = 0;
    // 3. Set Analog Mode Select bits for each Port (GPIOx->AMSEL = _PINs; 0=digital, 1=analog)
    // 4. Set Port Control Register for each Port (GPIOx->PCTL = PMCn << _PTCL_PINn, check the PCTL table)
    // 5. Set Alternate Function Select bits for each Port (GPIOx->AFSEL = _PINs; 0=regular I/O, 1=PCTL peripheral)
    // 6. Set Output pins for each Port (Direction of the Pins: GPIOx->DIR = _PINs; 0=input, 1=output)

    // 7. Set PUR bits for internal pull-up, PDR for pull-down reg, ODR for open drain (0: disable, 1=enable)

    // 8. Set Digital ENable register on all port.pins (GPIOx->DEN = _PINs; 0=disable, 1=enable)

}
//------------------------------------------------------------------------------
void StepperMotor(int s, bool direction)
{
    int i;

}
//------------------------------------------------------------------------------

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

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

void Setup_GPIO(void);

#define CW    0
#define CCW   1
void StepperMotor(int s, bool direction);
volatile uint32_t *Stepper = (uint32_t *)GPIO? + (_PIN? | .... );

//------------------------------------------------------------------------------
int main()
{
    int i = 0;

    Setup_GPIO();
    *Stepper = ____; // Step 0 value

    while(1){
        // If users press SW1, rotate CW for 5 steps

		// If users press SW2, rotate CCW for 5 steps

        DelayMs(200);
    }
}
//------------------------------------------------------------------------------
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 GPIO only PD7, PF0 on TM4C123G; PD7, PE7 on TM4C1294 (GPIOx->LOCK = 0x4C4F434B; and GPIOx->CR = _PINs;)
    // 3. Set Analog Mode Select bits for each Port (GPIOx->AMSEL = _PINs; 0=digital, 1=analog)
    // 4. Set Port Control Register for each Port (GPIOx->PCTL = PMCn << _PTCL_PINn, check the PCTL table)
    // 5. Set Alternate Function Select bits for each Port (GPIOx->AFSEL = _PINs; 0=regular I/O, 1=PCTL peripheral)
    // 6. Set Output pins for each Port (Direction of the Pins: GPIOx->DIR = _PINs; 0=input, 1=output)

    // 7. Set PUR bits for internal pull-up, PDR for pull-down reg, ODR for open drain (0: disable, 1=enable)

    // 8. Set Digital ENable register on all port.pins (GPIOx->DEN = _PINs; 0=disable, 1=enable)

}
//------------------------------------------------------------------------------
void StepperMotor(int s, bool direction)
{
    int i;

}
//------------------------------------------------------------------------------

Since the pins used for the stepper motor are assigned in the same port, the output values for the stepper motor can be stored in a one-dimensional array. To control the stepper motor's rotation and direction, read the values from the array in sequence and send them to the port.

The template and pseudocode for Stepper() function as below:

uint8_t   Steps1[] = {0x__, 0x__, 0x__, 0x__ };      // WAVE DRIVE: 1-Phase at a Time (Full-Step)

void StepperMotor(int s, bool direction)
{
    int i;

    // Implement the pPseudocode here

}

create variable: i
crease static variable: idx = 0

set i to 0

while-loop (i < s):
    if direction equal to CW
        increase idx by 1
    else
        decrease idx by 1
    endif

    // Check idx range
    if idx less than 0
        set idx to the array size - 1
    else if idx greater than or equal to the array size
        clear idx to 0
    endif

    set *Stepper to Steps1[idx] value
    increase i by 1
delay for 10 ms
endwhile

The mealy state machine can be used in this case. If the current state is in S_1 and the direction is CW, then the state translates to S_2 and sets the Stepper to step2 value. The state diagram is shown in Figure 2-1.

Note: In the main() function, the new initial value must be assigned to *Stepper in lin 24.

Figure 2-1: The Mealy State Diagram for Stepper Motor

Template code for state machine as below:

typedef enum STATES{
    S_1,
    S_2,
    S_3,
    S_4
} STATES;

uint8_t Steps2[] = {0x__, 0x__, 0x__, 0x__ }; // The array values of FULL STEP: 2 Phases at a Time (Full-Step)

void StepperMotor(int s, bool direction)
{
    int i;
    static STATES state = S_1;

    for (i = 0; i< s; i++){
        switch( state ) {
            case S_1:
                if (direction == CW){
                    state = ____;
                    *Stepper = ____;
                } else {

                }
            break;
            case S_2:

            break;
            case S_3:

            break;
            case S_4:

            break;
        }
        DelayMs(10);
    }
}

Now, use the Double-Linked List to implement the Stepper() function by using the Half step (using the "2-phase at a time" table).

Note: In the main() function, the new initial value must be assigned to *Stepper in lin 24. The number of steps for 120 degrees must be recalculated, and write the value in lines 27 and 30.

//------------------------------------------------------------------------------
int main()
{
    int i = 0;

    Setup_GPIO();
    *Stepper = ____; // Step 0 value

    while(1){
        for (i = 0; i < ____; i++)  // (steps for 120 degree) / 5
            StepperMotor(5, CW);
        DelayMs(500);
        for (i = 0; i < ____; i++)  // (steps for 120 degree) / 5
            StepperMotor(5, CCW);
        DelayMs(500);
    }
}
//------------------------------------------------------------------------------

The template and pseudocode for Stepper() function as below:

typedef struct STEPS{
    struct STEPS    *pre;
    uint8_t         data;
    struct STEPS    *next;
} STEPS;

STEPS Steps3[]={
    {_, _, _},      // Steps3[0] ==> {preLink, data, nextLink}
    {_, _, _},      // Steps3[1]
    {_, _, _},      // Steps3[2]
    {_, _, _},      // Steps3[3]
    {_, _, _},      // Steps3[4]
    {_, _, _},      // Steps3[5]
    {_, _, _},      // Steps3[6]
    {_, _, _}       // Steps3[7]
};

void StepperMotor(int s, bool direction)
{
    int             i;
    static STEPS*   p = Steps3;

    // Implement the Pseudocode here

}

clear i to 0
while-loop(i < s)
    if direction equal to CW
        set p to next link
    else
        set p to previous link
    endif

    set *Stepper to the data in the link
    increase i by 1

delay for 10 ms
endwhile