1 Continuous MCPWM at a time

[HenrikOlsson]

Hello,
I can't really see any problem with it.... What does doesn't work mean in this case, what does it do?

The only think I can think of is if you have anything else connected to PortA so that the actual value assigned to EncoderState1 isn't 0 even when the encoder is in the zero-position. But since it works with the IF-THEN version it can't be that (?).

Do you have a serial connection setup? If so you can HSEROUT some debug information which will make it easier to figure out what's going on. If not perhaps you could blink a LED the same number of times as the value that gets assigned to EncoderState1, just to see what's going on.

/Henrik.

[barneyfrance]

Hello,

Thank you for your reply,
The IF...THEN code still works (thanks for the tip putting just the subroutines at the top of main).

Do you have a serial connection setup? If so you can HSEROUT some debug information which will make it easier to figure out what's going on.

I am only using a PICkit 2 programmer. ?!

If not perhaps you could blink a LED the same number of times as the value that gets assigned to EncoderState1, just to see what's going on.

What do you mean ??


This morning I've tried a different code :

 
Main:
encoderstate1 = PORTA

        Select encoderstate1
        Case %000000
            GoSub GetADC
            GoSub SetPWM           
            OVDCOND = %00100010 'Q4 (PWM5) and Q10 (PWM1)
            PORTC = %00000011   'Q1 and Q7 ON   
        Case %000001
            GoSub GetADC
            GoSub SetPWM           
            OVDCOND = %00100010 'Q4 (PWM5) and Q10 (PWM1)
            PORTC = %00000011   'Q1 and Q7 ON
        Case Else 
            PORTC = 0
            OVDCOND = 0
        EndSelect

In case 0, it is doing what it should do, now if I'm trying to give the value of 1 (I have a switch on portA.0, that is all !!) it jumps to case else, it means that it does not see the value 1 ??? Why not ? it is working with IF... THEN...
Moreover, after switching my switch and giving the value 1 to portA.0, 4seconds after, it acts like if the value on portA.0 was 0... ???

AHHH sometimes those pics know how to make you crazy, doesn't they ?
Thanks for the help. Very much appreciated

[HenrikOlsson]

Hi,
It's strange if it really does work with the IF-THEN version. However, as is common on these PICs there are analog inputs on PortA. These normaly needs to be switched to digital in order to work in digital mode (no surprise) and this PIC is no exception. I know you're using the ADC in your GetADC rotuine so I know you have it setup some way or another but are you sure that the pins used for the encoder are setup as digital? (ANSEL0 and ANSEL1 registers)

My thought with the LED was something in the line of:

i VAR BYTE
LED VAR PortB.7
 
EncoderState1 = PortA
 
For i = 0 to EncoderState1
  High LED
  Pause 200
  Low LED
  Pause 200
NEXT
 
'Rest of code
 
Pause 2000  'Just to make a visual "mark" that the loop starts over
Goto Main

This should make the LED blink the number of times equal to the value loaded into EncoderState1. It should help you figure out what's going on.

My money is on the ADC being configured to have its inputs on some of the pins you're trying to use as digital. I don't know why it seems to work with the IF-THEN version though....

If this doesn't help can you post a schematic and the complete code?

/Henrik.

[barneyfrance]

Hello,

I'll try this as soon as I can. I have configured correctly ANSEL0 and ANSEL1 and I'm using my pot on AN6 in order to have all of my inputs encoder on portA.
Now, if this doesn't work i'll post my code and everything.
However is there anyway to switch off my commutation sequence anytime using IF.THEN ? for instance :

main : 
If switch=1 then
    if encoder=1 then
    PWM 1,2

    else if encoder = 2
    PWM 2,3     ==> I'm turning my Switch "Start/stop" here and I want the program to stop everything here and not wait the end of the loop ? 

    else if encoder= 3
    PWM 4,3
    Endif

Endif

Goto Main

[barneyfrance]

The case code now works, now idea what happened... ?
Now I have another question (I'm still interested about the one in the previous post).
When I move my motor forward, my encoder gives 12 different values, however, when I will operate it backward, I have still 12 steps but within these steps there are some similar values.
for example :
0, 32, 48, 56, 60, 62, 63, 62, 60, 56, 48, 32
Now for these 12 steps I need to activate different pins even though some values are the same, from my understanding, I will not be able to use select case / case in that "case" lol ?

[HenrikOlsson]

Hi,
What is this encoder you're using? Is it some kind of resolver with digital output? And why does the seqeunce change (not just reversing) when you reverese the direction of rotation? Or am I missunderstanding?

If knowing the intended direction of rotation isn't enough then I currently don't see how it's going to be done since the sequence is the same in both directions.

Are you sure you don't have a second output on that encoder? This looks like a low resolution sine-wave to me which leads me to belive what you have is some kind of SIN/COS resolver with a digital interface. (?) Do you have a datasheet you can link to?

The MCPWM module on the '4431 has dedicated faultinputs which can be setup to shut down the PWM. Either until the fault-input is cleared (good for cycle-by-cycle current limit) or untill a fault reset of the module is performed. Perhaps you could use that to stop the commutation. Otherwise you'll simply need to check the state of the switch as often as you need to - or use an external interrupt.

/Henrik.

[barneyfrance]

Hello,

Sorry for the late reply, it is nothing complicated like that. it is just 6 optical switches mounted on the rotor therefore 6 inputs on my pic that gives me a truth table. (in function of the inputs ON or OFF, I know what phases of the motor I need to turn ON/OFF).
For the clockwise rotation, it goes like this :
000000
000001
000011
000111
001111
011111
111111
111110
111100
etc

and for anti clockwise it goes like this :
000000
100000
110000
111000
111100
111110
111111
111110
111100
etc, as you can see for anti clockwise I am getting the same values but it is not the same phases ON, I need to turn ON (for 360 mechanical degrees, I have 3 times these 12 "cases").

Otherwise you'll simply need to check the state of the switch as often as you need to

Can you give me a simple example ?

Many thanks again for your answers