TM4C123gh6pm QEI error interfacing incremental encoder

Hello Dilraj

First of all please use TivaWare API instead of the DRM style of coding. In the last 24 hrs another DRM code has caused a blunder for both the OP and me.

Hello Amit

Here is code after modification , now used Tivaware API to configure QEI module.

#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_gpio.h"
#include "inc/hw_types.h"
#include "inc/hw_ints.h"
#include "inc/hw_memmap.h"
#include "driverlib/sysctl.h"
#include "driverlib/pin_map.h"
#include "driverlib/gpio.h"
#include "driverlib/qei.h"
#include "tm4c123gh6pm.h"

volatile int qeiPosition;

void forward(volatile int steps);
void reverse(volatile int steps);
void portfinit(void);
int main(void) {

// Set the clocking to run directly from the crystal.
SysCtlClockSet(SYSCTL_SYSDIV_2|SYSCTL_USE_PLL|SYSCTL_XTAL_25MHZ|SYSCTL_OSC_MAIN);

// Enable QEI Peripherals
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
SysCtlPeripheralEnable(SYSCTL_PERIPH_QEI0);


HWREG(GPIO_PORTD_BASE + GPIO_O_LOCK) = GPIO_LOCK_KEY;
HWREG(GPIO_PORTD_BASE + GPIO_O_CR) |= 0x80;
HWREG(GPIO_PORTD_BASE + GPIO_O_LOCK) = 0;

//Set Pins to be PHA0 and PHB0
GPIOPinConfigure(GPIO_PD6_PHA0);
GPIOPinConfigure(GPIO_PD7_PHB0);

//Set GPIO pins for QEI. PhA0 -> PD6, PhB0 ->PD7.
GPIOPinTypeQEI(GPIO_PORTD_BASE, GPIO_PIN_6 | GPIO_PIN_7);

//DISable peripheral and int before configuration
QEIDisable(QEI0_BASE);
QEIIntDisable(QEI0_BASE,QEI_INTERROR | QEI_INTDIR | QEI_INTTIMER | QEI_INTINDEX);


QEIEnable(QEI0_BASE); // Enable the quadrature encoder.

QEIPositionSet(QEI0_BASE, 00);

portfinit();


while (1) //This is the main loop of the program
{

unsigned long in;
in=GPIO_PORTF_DATA_R & 0X01;
if(in == 0x00) //checking Launchpad on-board switch status
{
forward (1000); //number of steps motor gas to move in forward direction
SysCtlDelay (900000);
SysCtlDelay (900000);
SysCtlDelay (900000);
reverse (1000); // number of steps motor has to take in reverse direction
SysCtlDelay (60000);
}
}
}

void forward (volatile int steps)
{

QEIPositionSet(QEI0_BASE, steps);
//QEIDisable(QEI0_BASE);
QEIConfigure(QEI0_BASE, (QEI_CONFIG_CAPTURE_A_B| QEI_CONFIG_NO_RESET |
QEI_CONFIG_QUADRATURE | QEI_CONFIG_NO_SWAP), 2399);

QEIEnable(QEI0_BASE);
while(QEI0_POS_R>50) //run motor until QEI0_POS_R is greater than 50
{
GPIO_PORTF_DATA_R = 0x02; //P2 direction, PF1 step for stepper motor
SysCtlDelay (35000);
GPIO_PORTF_DATA_R = 0x00;
SysCtlDelay (35000);
}


}
void reverse (volatile int steps)
{

QEIPositionSet(QEI0_BASE, steps);
QEIConfigure(QEI0_BASE, (QEI_CONFIG_CAPTURE_A_B | QEI_CONFIG_NO_RESET |
QEI_CONFIG_QUADRATURE | QEI_CONFIG_SWAP), 2399);
QEIEnable(QEI0_BASE);
while(QEI0_POS_R>50) //run motor until QEI0_POS_R is greater than 50
{
GPIO_PORTF_DATA_R = 0x06; // P2 direction, PF1 step for stepper motor
SysCtlDelay (35000);
GPIO_PORTF_DATA_R = 0x04;
SysCtlDelay (35000);
}

}

void portfinit(void) // configuring port F
{ volatile unsigned long delay;
GPIO_PORTF_LOCK_R |= 0X4C4F434B;
GPIO_PORTF_CR_R = 0X1F;
GPIO_PORTF_AMSEL_R =0X00;
GPIO_PORTF_DIR_R = 0X0E;
GPIO_PORTF_PUR_R = 0X11;
GPIO_PORTF_DEN_R = 0X1F;
}

Hello Amit

As far PD6 and PD7 are concerned, encoder is sending desirable outputs with internal pull-up.

I have configured QEI once in "void forward(volatile int steps)" function and then in "void reverse(volatile int steps)" function to swap INVA and INVB.

So do i have to disable QEI each time before configuring it then enable it ?

Since i am using encoder to sense rotation of a stepper motor and stepper motors tend to vibrate and oscillate at mean position, could this be a reason for error signal.

Regards
Dilraj Singh

Hello Dilraj

You do not need to swap. The QEI encoder will be able to figure out the change of direction based on the signal.

In reply to Amit Ashara:

Hello Amit

ThankYou ,But error is still there indication invalid greycode generated.

Regards
Dilraj Singh

Hello Dilraj

Can you please share the scope snapshot of the encoder output to the TM4C device and QEI configuration?

In reply to Amit Ashara:

Hello Amit

Actually I just hooked up LED's on phase A and phase B to see output, but i don't have scope to check output.

Regards
Dilraj Singh

Hello Dilraj

I would like to see scope snapshot and the QEI register configuration as given in Register Window of the IDE.

dilraj singh95 said:

As far PD6 and PD7 are concerned, encoder is sending desirable outputs with internal pull-up.

Your writing is unclear as to the location of those, "internal pull-ups."   If you speak to the MCU - those resistance values are high - it is likely that both rise & fall times land outside of specification.

While your "Led Monitor" may serve some (initial/preliminary) purpose - they too may overchallenge the encoder's output signals.  

Can you provide any insight into the "source or description" of the "QEI Error?"   Such report - w/out "any" detail - provides little (i.e. NO) value.

In summary - if employing the MCU's internal pull-ups replace them w/10K or less external ones - placed as close as possible to the MCU.   Remove your Led Monitors.  Repeat your test...

HI Amit

Thank You, As pointed by you, I was configuring QEI multiple times so I modified code to configure it only once and and it seems to resolve the problem. Here is modified code.

#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_gpio.h"
#include "inc/hw_types.h"
#include "inc/hw_ints.h"
#include "inc/hw_memmap.h"
#include "driverlib/sysctl.h"
#include "driverlib/pin_map.h"
#include "driverlib/gpio.h"
#include "driverlib/qei.h"
#include "tm4c123gh6pm.h"

volatile int qeiPosition;

void forward(volatile int steps);
void reverse(volatile int steps);
void portfinit(void);
int main(void) {

// Set the clocking to run directly from the crystal.
SysCtlClockSet(SYSCTL_SYSDIV_2|SYSCTL_USE_PLL|SYSCTL_XTAL_25MHZ|SYSCTL_OSC_MAIN);

// Enable QEI Peripherals
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
SysCtlPeripheralEnable(SYSCTL_PERIPH_QEI0);


HWREG(GPIO_PORTD_BASE + GPIO_O_LOCK) = GPIO_LOCK_KEY;
HWREG(GPIO_PORTD_BASE + GPIO_O_CR) |= 0x80;
HWREG(GPIO_PORTD_BASE + GPIO_O_LOCK) = 0;

//Set Pins to be PHA0 and PHB0
GPIOPinConfigure(GPIO_PD6_PHA0);
GPIOPinConfigure(GPIO_PD7_PHB0);

//Set GPIO pins for QEI. PhA0 -> PD6, PhB0 ->PD7.
GPIOPinTypeQEI(GPIO_PORTD_BASE, GPIO_PIN_6 | GPIO_PIN_7);

//DISable peripheral and int before configuration
QEIDisable(QEI0_BASE);
QEIIntDisable(QEI0_BASE,QEI_INTERROR | QEI_INTDIR | QEI_INTTIMER | QEI_INTINDEX);

QEIConfigure(QEI0_BASE, (QEI_CONFIG_CAPTURE_A_B| QEI_CONFIG_NO_RESET |
QEI_CONFIG_QUADRATURE | QEI_CONFIG_SWAP), 3999);
QEIPositionSet(QEI0_BASE, 50);
QEIEnable(QEI0_BASE);

portfinit();
unsigned long in;
unsigned long out;
unsigned long load;


while (1) //This is the main loop of the program
{

in=GPIO_PORTF_DATA_R & 0X01;
if(in == 0x00)
{



forward (1000);
SysCtlDelay (900000);
reverse (1000);
SysCtlDelay (900000);
}
}
}

void forward (volatile int steps)
{

// QEIPositionSet(QEI0_BASE, steps);
//QEIDisable(QEI0_BASE);

while(QEI0_POS_R<2500)
{
GPIO_PORTF_DATA_R = 0x02; // pf2 dir, p1 step
SysCtlDelay (25000);
GPIO_PORTF_DATA_R = 0x00;
SysCtlDelay (25000);
}


}
void reverse (volatile int steps)
{

// QEIPositionSet(QEI0_BASE, steps);
while(QEI0_POS_R>50)
{
GPIO_PORTF_DATA_R = 0x06; // pf2 dir, p1 step
SysCtlDelay (25000);
GPIO_PORTF_DATA_R = 0x04;
SysCtlDelay (25000);
}

}

void portfinit(void)
{ volatile unsigned long delay;
GPIO_PORTF_LOCK_R |= 0X4C4F434B;
GPIO_PORTF_CR_R = 0X1F;
GPIO_PORTF_AMSEL_R =0X00;
GPIO_PORTF_DIR_R = 0X0E;
GPIO_PORTF_PUR_R = 0X11;
GPIO_PORTF_DEN_R = 0X1F;
}

Hello Dilraj

Glad the issue is fixed. A good guideline for reconfiguration (normally not required), Is to disable the function, reconfigure and then enable it.