EPWM control

**mackrackit** · - 27th September 2007, 02:19

Off hand I do not see anything wrong with the logic, so check hardware.

Can you add to your code a quick debug out put---serot to hyperterm the values of Speed and AnalogLow/High or the ADC value of that pin?

The ADC with out the pot could float to mid range.

Along with the debug, check the voltages at the ADC pins(sure you have done this,basic trouble shooting).

Hard code Duty a a give value to check the output(if you have a spare pin --- add some where in the main loop--- if pin? then Duty = ?.

I know this is not much help but a the moment it is all I can suggest

**Asmith** · - 27th September 2007, 14:47

It's ok mackrackit any help is better than none. Here's where I'm at as of now. I have encorperated the rest of the code back into the main now. I've left out the section where I figure out the seeking value and hard coded it. I've also given position a hard coded value as with nothing attached to the pin I will get garbage on the pin. I still have a pot tied to AN5 which does change the DC as I move it up and down. If you look below there are 6 lines in the "timeTomove" sub, if I uncomment the first four only I get no output. If I uncomment out the bottom two I get a couple of pulses on the output (Maybe 2 of 3) but after that the signal drops out. Any ideas? I will continue to work on this, and thank you for the help so far.

Code:

'-------------------------------------------------------------------------'
'	PIC Defines Specific to PIC Basic Pro                                  '
'-------------------------------------------------------------------------'
   ' 1. Use internal system clock
   @ DEVICE PIC16F684, INTRC_OSC_NOCLKOUT 
   ' 2. Turn watchdog timer on
   @ DEVICE PIC16F684, WDT_OFF
   ' 3. Power on time on
   @ DEVICE PIC16F684, PWRT_ON
   ' 4. Turning off the master clear input
   @ DEVICE PIC16F684, MCLR_OFF
   ' 5. Brown out detect on
   @ DEVICE PIC16F684, BOD_ON
   ' 6. Data EE Read protect is off
   @ DEVICE PIC16F684, CPD_OFF
   ' 7. Code protect is off
   @ DEVICE PIC16F684, PROTECT_OFF

'-------------------------------------------------------------------------'
'	Hardware Defines Specific to PIC Basic Pro                             '
'-------------------------------------------------------------------------'
	define ADC_BITS 10          'Set A/D coverter to use 10 bits
   define ADC_SAMPLEUS 50      'Set A/D sample time as 50us
   DEFINE OSC 8                'Change clock speed to 8Mhz
   
'-------------------------------------------------------------------------'
'	Define Program Variables                                               '
'-------------------------------------------------------------------------'
   R VAR BYTE
   ScaledX VAR BYTE
   ScaledY VAR BYTE
   ShortX VAR BYTE
   ShortY VAR BYTE
   Slope VAR WORD
   
   AnalogLow VAR WORD          'Digital value for an analog low signal
   AnalogHigh VAR WORD         'Digital value for an analog high signal
   CurrentSpeed VAR WORD
   DUTY VAR WORD
   ExtLimit VAR WORD           'Stored value of the extend limit setting
   JoyX VAR WORD
   JoyY VAR WORD
   RetLimit VAR WORD           'Stored value of the retract limit setting
   Position VAR WORD           'Analog value of the internal potentiometer
   Seeking VAR WORD
   Speed VAR WORD

'-------------------------------------------------------------------------'
'	Define I/O and EEPROM Definitions                                      '
'-------------------------------------------------------------------------'
   
   data @0,word 768            'Set default extend limit
   data @2,word 256            'Set default retract limit    

   AnalogHigh = 768            'Set analog high signal level 
   AnalogLow = 256             'Set analog low signal level

'   READ 1, RetLimit.Highbyte
'   READ 0, RetLimit.Lowbyte
'   READ 3, ExtLimit.Highbyte
'   READ 2, ExtLimit.Lowbyte

'-------------------------------------------------------------------------'
'	Initialise PIC Hardware                                                '
'-------------------------------------------------------------------------'
   CMCON0 = 7                  'Turn comparators off
	ADCON0.7 = 1                'Set A/D Values to be right justified
   ADCON0.0 = 1                'Turn on A/D Converter
   ANSEL = %00110111           'Turn on select analog registers
	TRISA = %00001111           'Turn on select register inputs
	TRISC = %00111111           'Turn on select register inputs
    
   PR2 = 249
   CCP1CON = %11001100  
   CCPR1L = 0 
   PIR1.1 = 0
   T2CON.0 = 0
   T2CON.1 = 0
   T2CON.2 = 1
   WHILE (PIR1.1 = 0)
   WEND;
   TRISC = %00000011 
'-------------------------------------------------------------------------'
'   Start of Main Program                                                 '
'-------------------------------------------------------------------------'
Main:   
   ADCIN 1, JoyX
   JoyX.LowByte = ADRESL
   JoyX.HighByte = ADRESH
  
   ADCIN 0, JoyY
   JoyY.LowByte = ADRESL
   JoyY.HighByte = ADRESH 

   ShortX = JoyX / 4
   ShortY = JoyY / 4
   Seeking = 400
   GOTO TimeToMove

TimeToMove:
   ADCIN 2, Position
   Position.LowByte = ADRESL
   Position.HighByte = ADRESH

Position = 300

   If (Position < Seeking + 10) OR (Position > Seeking - 10) THEN
'      DUTY = 0
'      CCP1CON.4 = DUTY.0
'      CCP1CON.5 = DUTY.1 
'      CCPR1L = DUTY >> 2      
   ELSE 
      IF (Position > Seeking + 10) THEN
'         CCP1CON.7 = 1
         GOSUB GETSpeed
      ENDIF
      IF (Position < Seeking - 10) THEN
'         CCP1CON.7 = 0
         GOSUB GetSpeed
      ENDIF
   ENDIF
GOTO Main

GetSpeed:
   ADCIN 5, Speed
   Speed.lowbyte = ADRESL  
   Speed.highbyte = ADRESH    
   IF (Speed > AnalogLow) & (Speed < AnalogHigh) THEN
      DUTY = 617
      CCP1CON.4 = DUTY.0
      CCP1CON.5 = DUTY.1 
      CCPR1L = DUTY >> 2
   ENDIF
   IF (Speed < AnalogLow) THEN
      DUTY = 400
      CCP1CON.4 = DUTY.0
      CCP1CON.5 = DUTY.1 
      CCPR1L = DUTY >> 2
   ENDIF
   IF (Speed > AnalogHigh) THEN
      DUTY = 850
      CCP1CON.4 = DUTY.0
      CCP1CON.5 = DUTY.1 
      CCPR1L = DUTY >> 2
   ENDIF
RETURN

END

**mackrackit** · - 28th September 2007, 01:37

After DUTY gets a value in the main part of the program you have DUTY=0 in timeTOmove.

The code you have working writes to the high and low byte for Speed the goes straight to CCP1CON.4 and CCP1CON.5 with the low and high byte of speed.

In the one that is not working DUTY has 0 written to it before CCP1CON.4 and CCP1CON.5.

**Asmith** · - 28th September 2007, 15:45

The part of the code I last posted that has 0 being put into DUTY is there to stop the motor from running. The position is between the two required points so I want to stop motion. The other two if statments is is the motor is not in the correct position then it needs to move. To do that you change the CCP1CON.7 pin to either a 1 or 0 for full H-bridge mode, and use the standard duty cycle. It's just a way so I do not have to shut down the PWM and leave it running forever.

I will be working on this all day today, and try to give an update as I progress. If you have anything at all please let me know, I'm starting to run out of ideas. Thanks again.

**mister_e** · - 28th September 2007, 23:55

mmm, something spring to mind now form your first post, you said it was suppose to produce 8KHz but, in real-world, it produce 4KHz.

DEFINE OSC 8 don't change the internal OSC speed, it's more a compiler directive to match PAUSE, PAUSEus and all other timed stuff with the real OSC speed.

POR value for the internal osc is 4 MHZ, to change it to 8 MHZ you want to use

Code:

OSCCON = %01110000    ' this set the internal osc to 8MHz

for now i can't check the whole thing here, but let us know if the above fix something. At very least, you should have the right PWM frequency.

HTH

**Asmith** · - 1st October 2007, 14:53

Thank you Mister_e, that did help out. The running frequency is now 8KHz. I ran a small bit of code below.

Code:

'-------------------------------------------------------------------------'
'	PIC Defines Specific to PIC Basic Pro                                  '
'-------------------------------------------------------------------------'
   ' 1. Use internal system clock
   @ DEVICE PIC16F684, INTRC_OSC_NOCLKOUT 
   ' 2. Turn watchdog timer on
   @ DEVICE PIC16F684, WDT_OFF
   ' 3. Power on time on
   @ DEVICE PIC16F684, PWRT_ON
   ' 4. Turning off the master clear input
   @ DEVICE PIC16F684, MCLR_OFF
   ' 5. Brown out detect on
   @ DEVICE PIC16F684, BOD_ON
   ' 6. Data EE Read protect is off
   @ DEVICE PIC16F684, CPD_OFF
   ' 7. Code protect is off
   @ DEVICE PIC16F684, PROTECT_OFF

'-------------------------------------------------------------------------'
'	Hardware Defines Specific to PIC Basic Pro                             '
'-------------------------------------------------------------------------'
	define ADC_BITS 10          'Set A/D coverter to use 10 bits
   define ADC_SAMPLEUS 50      'Set A/D sample time as 50us
   DEFINE OSC 8                'Change clock speed to 8Mhz
   OSCCON = %01110000          'Change internal osc to 8MHz
'-------------------------------------------------------------------------'
'	Define Program Variables                                               '
'-------------------------------------------------------------------------'
   R VAR BYTE
   ScaledX VAR BYTE
   ScaledY VAR BYTE
   ShortX VAR BYTE
   ShortY VAR BYTE
   Slope VAR WORD
   
   AnalogLow VAR WORD          'Digital value for an analog low signal
   AnalogHigh VAR WORD         'Digital value for an analog high signal
   CurrentSpeed VAR WORD
   DUTY VAR WORD
   ExtLimit VAR WORD           'Stored value of the extend limit setting
   JoyX VAR WORD
   JoyY VAR WORD
   RetLimit VAR WORD           'Stored value of the retract limit setting
   Position VAR WORD           'Analog value of the internal potentiometer
   Seeking VAR WORD
   Speed VAR WORD

'-------------------------------------------------------------------------'
'	Define I/O and EEPROM Definitions                                      '
'-------------------------------------------------------------------------'
   data @0,word 768            'Set default extend limit
   data @2,word 256            'Set default retract limit    

   AnalogHigh = 768            'Set analog high signal level 
   AnalogLow = 256             'Set analog low signal level
   ExtLimit = 750
   Retlimit = 50
'-------------------------------------------------------------------------'
'	Initialise PIC Hardware                                                '
'-------------------------------------------------------------------------'
   CMCON0 = 7                  'Turn comparators off
	ADCON0.7 = 1                'Set A/D Values to be right justified
   ADCON0.0 = 1                'Turn on A/D Converter
   ANSEL = %00110111           'Turn on select analog registers
	TRISA = %00001111           'Turn on select register inputs
	TRISC = %00111111           'Turn on select register inputs
    
   PR2 = 249
   CCP1CON = %11001100  
   CCPR1L = 0 
   PIR1.1 = 0
   T2CON.0 = 0
   T2CON.1 = 0
   T2CON.2 = 1
   WHILE (PIR1.1 = 0)
   WEND;
   TRISC = %00000011 
'-------------------------------------------------------------------------'
'   Start of Main Program                                                 '
'-------------------------------------------------------------------------'
Main:   

WHILE(1)
   CCP1CON.7 = 1
   DUTY = 300
   CCP1CON.4 = DUTY.0
   CCP1CON.5 = DUTY.1 
   CCPR1L = DUTY >> 2
   PAUSE 1000
   DUTY = 0
   CCP1CON.4 = DUTY.0
   CCP1CON.5 = DUTY.1 
   CCPR1L = DUTY >> 2
   PAUSE 200
   
   CCP1CON.7 = 0
   DUTY = 300
   CCP1CON.4 = DUTY.0
   CCP1CON.5 = DUTY.1 
   CCPR1L = DUTY >> 2
   PAUSE 1000
   DUTY = 0
   CCP1CON.4 = DUTY.0
   CCP1CON.5 = DUTY.1 
   CCPR1L = DUTY >> 2
   PAUSE 200   
WEND

END

This ran a few times on the motor back and forth, and then ruined one of the driver chips on the board shorting my pcb out. This is an update of where I am at the moment. I starting trouble shooting on it now, so hopefully if anyone finds a solution so will I. One of the things that might be hurting me is a electro cap on the 5V rail (I know duh) or a very high uF cap on the +12V rail for the 2 H-bridges running DC brush motors. (Again, I can't believe I forgot these) I'm also attaching the schematic as this might help some see something in the hardware. I really appreciate all of the help so far guys. Thank you

Anthony

**mister_e** · - 1st October 2007, 16:31

Seems you forgot the back EMF diode in your H-Bridge driver.

470 Ohm seems a bit bit high for a gate resistor... if even really needed...

How many amp you need to drive?

Did you also tried with a resistive load?

I'll look the whole thing later, sure i missed something else.

Fortunately, someone else may beat me to the punch

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