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Weird Ticker Behavior Inside Class

11 Oct 2014

During program development I simply created my entire program within a single file, "main.cpp". However, my ultimate goal is to create a class library. This library is being used to control a simple 2-wheeled robot that is being controlled by a Nucleo F401RE board & custom motor shield.

My single file program works great. I am using a Ticker that interrupts every 205 microseconds in order to calculate motor velocity by using encoder feedback. I also use this event to update the tone on a piezo buzzer.

After converting my program into a class library I discovered that the Ticker would interrupt several times upon startup, but then would stop working. Not sure if I am doing something wrong?

main.cpp

#include "mbed.h"
#include "Apeiros.h"

Apeiros apeiros(SERIAL_TX, SERIAL_RX);

int main() {
    
    // Play initialize buzzer tones. //
    apeiros.SetBuzzerTone(1);
    wait_ms(250);
    apeiros.SetBuzzerTone(10);
    wait_ms(250);
    apeiros.SetBuzzerTone(1);
    wait_ms(250);
    apeiros.SetBuzzerTone(0);
    
    while(1) {
        
        if (apeiros.isSerialDataAvail()) apeiros.ParseUartData();
        
    }
}

Apeiros.h

#ifndef APEIROS_H
#define APEIROS_H
 
#include "mbed.h"
 
#define Dwh 2.621       // wheel diameter
#define PI 3.14159      // PI
#define Cwh (Dwh * PI)  // wheel circumference
#define TSCALE 10       // convert to 10ths of an inch
#define INVTICK 4883    // this is 1 / 204.8 us, to avoid using floating point math
#define NCLKS 128       // number of encoder clocks per wheel rotation
#define Ktps ((Cwh * TSCALE * INVTICK) / NCLKS)
#define MaxMotorSpeed 255

#define MIN_GRIPPER_PULSE 1000
#define MAX_GRIPPER_PULSE 2300

#define MAX_BUZZER_PWM 100
 
class Apeiros : public Serial{

public:
    Apeiros(PinName tx, PinName rx);
    bool isSerialDataAvail(void);
    void ParseUartData(void);    
    void SetBuzzerTone(int buzzerTone);
    void SetMotorSpeed(int leftMotorSpeed, int rightMotorSpeed);
    void SetGripperPosition(int pulseWidth_us);
    
private:
    
    AnalogIn ad_0;
    AnalogIn ad_1;
    AnalogIn ad_2;
    AnalogIn ad_3;
    AnalogIn ad_4;
    AnalogIn ad_5;

    DigitalOut buzzerOut;

    DigitalOut SN_3A;
    DigitalOut SN_4A;

    DigitalOut SN_2A;
    DigitalOut SN_1A;

    DigitalIn leftFrontIR;
    DigitalIn centerFrontIR;
    DigitalIn rightFrontIR;

    DigitalIn leftEncoderDirPin;
    DigitalIn rightEncoderDirPin;
    
    InterruptIn leftEncoderClk;
    InterruptIn rightEncoderClk;
    
    PwmOut rightMotorPWM;
    PwmOut leftMotorPWM;
    PwmOut gripperPWM;
    
    Ticker motorControl;
    
    volatile char rxBuff[16];
    volatile char rxBuffIndx;
    volatile char tmpRxBuff[16];
    volatile bool uartDataRdy;
    
    volatile int motorUpdateTickCount;
    volatile int motionLoopCount;
    
    volatile int leftEncoderCount;
    volatile int rightEncoderCount;
    volatile bool leftEncoderDir;
    volatile bool rightEncoderDir;
    volatile int leftMotorOffset;
    volatile int rightMotorOffset;
    
    volatile unsigned short analogIndex;
    volatile float adSensors[6];
    
    volatile char encoderArrayIndex_L, encoderArrayIndex_R;
    volatile int encoderPeriodArray_L[4], encoderPeriodArray_R[4];
    volatile int encoderPeriod_L, encoderPeriod_R, encoderPeriodSum_L, encoderPeriodSum_R;
    volatile int prevT3Count_L, prevT3Count_R;
    volatile bool encoderUpdated_L, encoderUpdated_R;
    volatile int encoderSpeed_L, encoderSpeed_R;
    
    // Buzzer Variables //
    volatile int buzzerPeriod;
    volatile int buzzerDuty;
    volatile int buzzerTick;
    volatile bool enableBuzzer;

    void getUartData(void);
    void motorControlISR(void);
    void leftEncoderTick(void);
    void rightEncoderTick(void);
    
    void ParseMotorCommand(void);
    void ParseBuzzerCommand(void);
    void ParseGripperCommand(void);
    void CalculateWheelSpeed(void);

};
 
#endif

Apeiros.cpp

#include "Apeiros.h"
#include "mbed.h"

//------------------------------------------------------------------------
// Constructor for Apeiros Class.                  
//------------------------------------------------------------------------
Apeiros::Apeiros(PinName tx, PinName rx) : Serial(tx,  rx), ad_0(PA_0), ad_1(PA_1),ad_2(PA_4),ad_3(PB_0),ad_4(PC_1),ad_5(PC_0),buzzerOut(PA_5),
SN_3A(PB_5),SN_4A(PC_7),SN_2A(PB_3),SN_1A(PA_8),leftFrontIR(PC_15),centerFrontIR(PC_14),rightFrontIR(PC_13),leftEncoderDirPin(PA_6),
rightEncoderDirPin(PA_7),leftEncoderClk(PH_1),rightEncoderClk(PH_0),rightMotorPWM(PB_10),leftMotorPWM(PB_4),gripperPWM(PB_6)
{   
    // Set direction of PWM dir pins to be low so robot is halted. //
    SN_3A = 0;
    SN_4A = 0;
    SN_2A = 0;
    SN_1A = 0;
    
    // Configure Left & Right Motor PWMs. //
    rightMotorPWM.period_us(255);
    rightMotorPWM.pulsewidth_us(0);    
    leftMotorPWM.period_us(255);
    leftMotorPWM.pulsewidth_us(0);
    
    // Configure Gripper PWM. //
    gripperPWM.period_ms(20);
    SetGripperPosition(2300);
    
    // Configure Wheel Encoder Inputs & ISRs. //
    leftEncoderDirPin.mode(PullUp);
    rightEncoderDirPin.mode(PullUp);
    leftEncoderClk.mode(PullDown);
    rightEncoderClk.mode(PullUp);  
    leftEncoderClk.rise(this, &Apeiros::leftEncoderTick);
    rightEncoderClk.fall(this, &Apeiros::rightEncoderTick);
    motorControl.attach_us(this, &Apeiros::motorControlISR, 205);
    
    Serial::attach(this, &Apeiros::getUartData,Serial::RxIrq);
    baud(115200);
    
    printf("\r\n");
    printf("Hello, my name is Apeiros!\r\n");
    
    rxBuffIndx = 0;
    uartDataRdy = false;
    motorUpdateTickCount = 0;
    motionLoopCount = 0;
    
    leftEncoderCount = 0;
    rightEncoderCount = 0;
    leftEncoderDir = 1;
    rightEncoderDir = 1;
    leftMotorOffset = 120;
    rightMotorOffset = 115;
    
    analogIndex = 0;
    buzzerPeriod = 2;
    buzzerDuty = buzzerPeriod/2;
    buzzerTick = 0;
    enableBuzzer = false;
}

//------------------------------------------------------------------------
// Serial Interrupt Service Routine (ISR) for RawSerial.                  
//------------------------------------------------------------------------
void Apeiros::getUartData()
{    
    if (!uartDataRdy)
    { 
      rxBuff[rxBuffIndx] = getc();
      
      if (rxBuff[rxBuffIndx] == 13)
      {
        for (rxBuffIndx = 0; rxBuffIndx < 16; rxBuffIndx ++) tmpRxBuff[rxBuffIndx] = rxBuff[rxBuffIndx];
        rxBuffIndx = 0;
        uartDataRdy = true;
       }   
       else
       {
            rxBuffIndx++;
            if (rxBuffIndx > 15) 
            {
               rxBuffIndx = 0;
               for (int indx=0;indx<16;indx++) rxBuff[indx] = 0;
            }
       }
    }
}

//------------------------------------------------------------------------
// Motor Control Interrupt Service Routine (ISR).
//------------------------------------------------------------------------
void Apeiros::motorControlISR()
{
    motorUpdateTickCount++;
    motionLoopCount++;
    
    if (motionLoopCount > 250)
    {
        CalculateWheelSpeed();
        motionLoopCount = 0;
    }
    
    // Update analog conversions. //
    switch (analogIndex)
    {
        case 0:
         adSensors[0] = ad_0.read();
         break;
        
        case 1:
         adSensors[1] = ad_1.read();
         break;
        
        case 2:
         adSensors[2] = ad_2.read();
         break;
        
        case 3:
         adSensors[3] = ad_3.read();
         break;
        
        case 4:
         adSensors[4] = ad_4.read();
         break;
        
        case 5:
         adSensors[5] = ad_5.read();
         break;        
    }
    analogIndex++;
    if (analogIndex > 5) analogIndex = 0;
    
    // Update buzzer tone as needed. //
    if (enableBuzzer)
    {
        buzzerTick++;
        if (buzzerTick > buzzerPeriod)
        {
            buzzerTick = 0;
            buzzerOut = 1;
        }
        else if (buzzerTick > buzzerDuty)
        {
            buzzerOut = 0;
        }
    }
}

//------------------------------------------------------------------------
// Interrupt Service Routine (ISR) for Left Wheel Encoder Transitions.                     
//------------------------------------------------------------------------
void Apeiros::leftEncoderTick()
{
    leftEncoderDir = leftEncoderDirPin.read();
    if (!leftEncoderDir) leftEncoderCount++;
    else leftEncoderCount--;
    
    // Remove the oldest value from the sum.
    encoderPeriodSum_L -= encoderPeriodArray_L[encoderArrayIndex_L];
    
    // Store the newest value, and add it to the sum.
    encoderPeriodSum_L += encoderPeriodArray_L[encoderArrayIndex_L] = motorUpdateTickCount - prevT3Count_L;
    
    // Calculate a new average period.
    encoderPeriod_L = encoderPeriodSum_L/4;
    
    // Move to the next array position.
    encoderArrayIndex_L++;                   
    if (encoderArrayIndex_L > 3) encoderArrayIndex_L = 0;
      
    // Store the current timer3TickCount for next time.
    prevT3Count_L = motorUpdateTickCount;
    
    // Set encoder as updated. 
    encoderUpdated_L = true;
}

//------------------------------------------------------------------------
// Interrupt Service Routine (ISR) for Right Wheel Encoder Transitions.                     
//------------------------------------------------------------------------
void Apeiros::rightEncoderTick()
{
    rightEncoderDir = rightEncoderDirPin.read();
    if (!rightEncoderDir) rightEncoderCount--;
    else rightEncoderCount++;
    
    // Remove the oldest value from the sum.
    encoderPeriodSum_R -= encoderPeriodArray_R[encoderArrayIndex_R];
    
    // Store the newest value, and add it to the sum.
    encoderPeriodSum_R += encoderPeriodArray_R[encoderArrayIndex_R] = motorUpdateTickCount - prevT3Count_R;
    
    // Calculate a new average period.
    encoderPeriod_R = encoderPeriodSum_R/4;
    
    // Move to the next array position.
    encoderArrayIndex_R++;                   
    if (encoderArrayIndex_R > 3) encoderArrayIndex_R = 0;
      
    // Store the current timer3TickCount for next time.
    prevT3Count_R = motorUpdateTickCount;   
    
    // Set encoder as updated. 
    encoderUpdated_R = true;
}

//------------------------------------------------------------------------
// Function to return status of UART data.
//------------------------------------------------------------------------
bool Apeiros::isSerialDataAvail()
{
    if (uartDataRdy) return true;
    else return false;
}

//------------------------------------------------------------------------
// Function to parse UART data from Rx buffer for SDIO1 (PA9 & PA10).                     
//------------------------------------------------------------------------
void Apeiros::ParseUartData()
{    
    switch (tmpRxBuff[0]){

       case 'A':
        printf("Sensors = (%0.2f, %0.2f, %0.2f, %0.2f, %0.2f, %0.2f)\r\n", adSensors[0], adSensors[1], adSensors[2], adSensors[3], adSensors[4], adSensors[5]);
        break;
        
       case 'B':
        ParseBuzzerCommand();
        printf("b\r\n");
        break;
                
       case 'D':
        printf("Sensors = (%d, %d, %d)\r\n", leftFrontIR.read(), centerFrontIR.read(), rightFrontIR.read());
        break;

       case 'E':
        printf("Encoder Ticks = %d, %d\r\n",leftEncoderCount, rightEncoderCount);
        break;
                
       case 'G':
        ParseGripperCommand();
        printf("g\r\n");
        break;
        
       case 'H':
        SetMotorSpeed(0, 0);
        printf("h\r\n");
        break;
       
       case 'M':
        ParseMotorCommand();
        printf("ma\r\n");
        break;
       
       case 'V':
        printf("Motor Velocity = %d, %d\r\n",encoderSpeed_L, encoderSpeed_R);
        break;
       
       case 'Y':
        gripperPWM.pulsewidth_us(2000);
        printf("ya\r\n");
        break;
        
       case 'Z':
        gripperPWM.pulsewidth_us(1000);
        printf("za\r\n");
        break;
        
       default:
        printf("Cmd unrecognized!\r\n");
        break;
    }   
    
    for (int buffIndx = 0; buffIndx < 16; buffIndx++) tmpRxBuff[buffIndx] = 0;
    
    uartDataRdy = false;
}

//------------------------------------------------------------------------
// Function to set tone of buzzer.
//------------------------------------------------------------------------
void Apeiros::SetBuzzerTone(int buzzerTone)
{
    if (buzzerTone > 0)
    {
        if (buzzerTone > MAX_BUZZER_PWM) buzzerTone = MAX_BUZZER_PWM;
        buzzerTick = 1;
        buzzerPeriod = buzzerTone;
        buzzerDuty = buzzerPeriod/2;
        enableBuzzer = true;
    }
    else
    {
        enableBuzzer = false;
        buzzerOut = 0;
    }
}

//------------------------------------------------------------------------
// Calculate Wheel Speeds                                                        
//                                                                            
// Speed in 0.1"/sec = (Cwh / NCLKS) * TSCALE / (TICK * PER) = Ktps / PER     
// where Cwh = 8.12" wheel circumference, NCLKS = 128 (32 stripe disk),       
// TSCALE = 10 (to convert inches to 0.1"), TICK = 205us per timer2 tick,     
// and PER is the measured period in timer 2 ticks                            
// Ktps = 3098                                                                
//------------------------------------------------------------------------
void Apeiros::CalculateWheelSpeed()
  {
    // If the wheel is spinning so slow that we don't have current reading.
    if (!encoderUpdated_R) encoderPeriod_R = motorUpdateTickCount - prevT3Count_R;  // Calculate period since last update.
    else encoderUpdated_R = false;  // Otherwise use it.

    // Converts from 205us ticks per edge to multiples of 0.1 inches per second.
    encoderSpeed_R = (signed short)(Ktps / encoderPeriod_R); 

    // Check direction of wheel rotation & adjust as needed. */
    if (!rightEncoderDir) encoderSpeed_R = -encoderSpeed_R;

    if (!encoderUpdated_L) encoderPeriod_L = motorUpdateTickCount - prevT3Count_L;
    else encoderUpdated_L = false;

    // Converts from 205us ticks per edge to multiples of 0.1 inches per second
    encoderSpeed_L = (signed short)(Ktps / encoderPeriod_L);

    // Check direction of wheel rotation & adjust as needed. */
    if (leftEncoderDir) encoderSpeed_L = -encoderSpeed_L;
  }

//------------------------------------------------------------------------
// Function to set left & right motor speed and direction.
//------------------------------------------------------------------------
void Apeiros::SetMotorSpeed(int leftMotorSpeed, int rightMotorSpeed)
{
 
 int tmpLeftSpeed = 0;
 int tmpRightSpeed = 0;
 
 if (rightMotorSpeed < 0)
 {
    SN_2A = 0;
    SN_1A = 1;
 } else {
    SN_2A = 1;
    SN_1A = 0; }
 
 if (leftMotorSpeed < 0)
 {
    SN_3A = 0;
    SN_4A = 1;
 } else {
    SN_3A = 1;
    SN_4A = 0; }
  
  if (leftMotorSpeed != 0) tmpLeftSpeed = abs(leftMotorSpeed) + leftMotorOffset;
  else
  {
      tmpLeftSpeed = 0;
      SN_3A = SN_4A = 0;
  }
  
  if (rightMotorSpeed != 0) tmpRightSpeed = abs(rightMotorSpeed) + rightMotorOffset;
  else
  {
      tmpRightSpeed = 0;
      SN_1A = SN_2A = 0;
  }
  
  if (tmpLeftSpeed > MaxMotorSpeed) tmpLeftSpeed = MaxMotorSpeed;
  if (tmpRightSpeed > MaxMotorSpeed) tmpRightSpeed = MaxMotorSpeed;
  
  leftMotorPWM.pulsewidth_us(tmpLeftSpeed);
  rightMotorPWM.pulsewidth_us(tmpRightSpeed);
    
}

//------------------------------------------------------------------------
// Function to parse motor commands from UART data.                     
//------------------------------------------------------------------------
void Apeiros::ParseMotorCommand()
{
   unsigned int commaPos, endPos, index1, index2;
   signed short leftWheel, rightWheel;
   char charBuff[5];
   bool foundNegative = false;
   
   commaPos = 0;
   endPos = 0;
   
   // Find comma position and return char.
    for (index1=2;index1<16;index1++)
    {
      if (tmpRxBuff[index1] == ',') commaPos = index1;
      else if (tmpRxBuff[index1] == 13)
      {
        endPos = index1;
        break;
      }
    }
    
    // Parse out left motor data.
    for (index1=0;index1<5;index1++) charBuff[index1] = ' ';
    index2 = 0;
    for (index1=2;index1<commaPos;index1++)
    {
      if (tmpRxBuff[index1] != '-') charBuff[index2] = tmpRxBuff[index1];
      else foundNegative = true;
      index2++; 
    }
    leftWheel = atol(charBuff);
    if (foundNegative) leftWheel = -leftWheel;
    
    foundNegative = false;
    
    // Parse out right motor data.
    for (index1=0;index1<5;index1++) charBuff[index1] = ' ';
    index2 = 0;
    for (index1=commaPos+1;index1<endPos;index1++)
    {
      if (tmpRxBuff[index1] != '-') charBuff[index2] = tmpRxBuff[index1];
      else foundNegative = true;
      index2++;
    }
    rightWheel = atol(charBuff);
    if (foundNegative) rightWheel = -rightWheel;
    
    //stdio1.printf("Left Motor = %d\r\n", leftWheel);
    //stdio1.printf("Right Motor = %d\r\n", rightWheel);
    
    SetMotorSpeed(leftWheel, rightWheel);
}

//------------------------------------------------------------------------
// Function to parse buzzer tone commands from UART data.                     
//------------------------------------------------------------------------
void Apeiros::ParseBuzzerCommand()
{
    unsigned int index1, index2, endPos;
    unsigned int buzzerTonePWM;
    char charBuff[3];
    
    index1 = index2 = endPos = 0;
    buzzerTonePWM = 1;
    
    for (index1=0;index1<3;index1++) charBuff[index1] = ' ';
    
    // Find position of return char.
    for (index1=1;index1<16;index1++)
    {
      if (tmpRxBuff[index1] == 13)
      {
        endPos = index1;
        break;
      }
    }
    
    index2 = 0;
    for (index1=1;index1<endPos;index1++)
    {
      charBuff[index2] = tmpRxBuff[index1];
      index2++; 
    }
    
    buzzerTonePWM = atol(charBuff);
    SetBuzzerTone(buzzerTonePWM);
}

//------------------------------------------------------------------------
// Function to parse gripper servo commands from UART data.                     
//------------------------------------------------------------------------
void Apeiros::ParseGripperCommand()
{
    unsigned int index1, index2, endPos;
    unsigned int gripperPosition;
    char charBuff[4];
    
    index1 = index2 = endPos = 0;
    gripperPosition = 2000;
    
    for (index1=0;index1<4;index1++) charBuff[index1] = ' ';
    
    // Find position of return char.
    for (index1=1;index1<16;index1++)
    {
      if (tmpRxBuff[index1] == 13)
      {
        endPos = index1;
        break;
      }
    }
    
    index2 = 0;
    for (index1=1;index1<endPos;index1++)
    {
      charBuff[index2] = tmpRxBuff[index1];
      index2++; 
    }
    
    gripperPosition = atol(charBuff);
    SetGripperPosition(gripperPosition);
}

//------------------------------------------------------------------------
// Function to set gripper servo position using supplied pulsewidth[us].                     
//------------------------------------------------------------------------
void Apeiros::SetGripperPosition(int pulseWidth_us)
{
    if (pulseWidth_us > MAX_GRIPPER_PULSE) pulseWidth_us = MAX_GRIPPER_PULSE;
    if (pulseWidth_us < MIN_GRIPPER_PULSE) pulseWidth_us = MIN_GRIPPER_PULSE;
    
    gripperPWM.pulsewidth_us(pulseWidth_us);
}
11 Oct 2014

Resolved my issue with the ticker by simply attaching the ticker in a begin method that is called before using my Apeiros class. Now the ticker interrupts as expected.

main.cpp

#include "mbed.h"
#include "Apeiros.h"

Apeiros apeiros(SERIAL_TX, SERIAL_RX);

int main() {
    
    apeiros.Begin();
    
    while(1) {
        
        if (apeiros.isSerialDataAvail()) apeiros.ParseUartData();
    }
}

Apeiros.cpp

//------------------------------------------------------------------------
// Function to Begin.                     
//------------------------------------------------------------------------
void Apeiros::Begin()
{
    motorControl.attach_us(this, &Apeiros::motorControlISR, 205);
    
    printf("\r\n");
    printf("Hello, my name is Apeiros!\r\n");
    
    // Play initialize buzzer tones. //
    SetBuzzerTone(1);
    wait_ms(250);
    SetBuzzerTone(10);
    wait_ms(250);
    SetBuzzerTone(1);
    wait_ms(250);
    SetBuzzerTone(0);
}

Regards, Abe

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