1 Continuous MCPWM at a time

[HenrikOlsson]

Hi,
OK, if I get this right it should be enough to remember the previous state of the input.

FWD: 0,1,3,7,15,31,63,62,60,56,48,32
REV: 0,32,48,56,60,62,63,31,15,7,3,1

If the current state is 15 and the previous state is 7 we're going forward, if the current state is 15 and the previous state is 31 we're going backwards.

EncoderState = PortA
If EncoderState <> OldState THEN  ' Don't run commutation code if shaft hasn't moved. 
 
Select Case EncoderState
 
Case 0
  If OldState = 32 THEN  'We're moving FWD
  'Code for FWD
  ELSE
  'Code foe REV
  ENDIF

Case 1
  If OldState = 0 THEN   'We're moving forward
  'Code for FWD
  ELSE
  'Code for REV
  ENDIF
 
Case 3
  If OldState = 1 THEN   'We're moving forward
  'Code for FWD
  ELSE
  'Code for REV
  ENDIF
 
' And so on for all twelve states.
 
OldState = EncoderState  'Remember current state.
ENDIF

As for the switch, I just mean that if you don't think it's enough to check at the beginning of the loop you'll have to check it as often as you think is neccessary, for example in each case statement. Personally I think that it's enought to check it one time in the main loop since only one of the Case blocks will get executed anyway. But I may have missed something.

[barneyfrance]

mhhh that sounds great !!! this will work I think ! I have a switch that tells me to go forward or backward I can add it to this !
yes effectively the switch at the top of the loop in "case code" is enough.
However when I start my pic it won't move, will it ? because no previous state ? or am I missing something ?

[HenrikOlsson]

That's correct, since the shaft can be in any location on powerup you need to establish the proper encoderstate at bootup and then initialise OldState to the apropriate value depending on the desired direction of rotation - before entering the Main routine. You could do it with something like this but please doublecheck the sequence here, I'm not sure I've got it right.

'Get index of current encoderstate, Temp will be 0-11
Lookdown EncoderState, [0,1,3,7,15,31,63,62,60,56,48,32],Temp
 
'Now initialise OldState to correct value depending on desired direction of rotation.
If DesiredDirection = Forward THEN
  Lookup Temp, [32,0,1,3,7,15,31,63,62,60,56,48], OldState
ELSE
  LookUp Temp, [1,0,7,15,31,63,62,60,56,48,32], OldState
EndIf

[barneyfrance]

thx i'll keep try that in the morning =)

[barneyfrance]

actually this can't work because my reverse values are :
0, 32, 48, 60, 62, 63, 62, 60, 56, 48, 32....
I'm getting desesperate with these switches...

[barneyfrance]

fwd values : 0, 1, 3, 7, 15, 31, 63, 62, 60, 56, 48, 32
reverse values : 0, 32, 48, 60, 62, 63, 62, 60, 56, 48, 32

I have 2 truth tables with switches to turn on/off for these values.
Now i have a pot and a switch start/stop and a switch fwd/reverse..
Now we should not be able to change the sequence commutation if the pot is not 0 so I did a little code like this :

Direction VAR bit
direction = 0

Main:

        encoderstate1 = PORTA
        
        GoSub GetADC
        
        If ADRESH = 0 Then 'value of the pot stored in ADRESH
            If ADRESL = 0 Then ''value of the pot stored in ADRESH
                direction = PORTE.1 'switch for direction
            EndIf
        EndIf

if encoderstate = 0  then
'switches turn ON/OFF
elseif encoderstate = 1 then 
'switches turn on OFF
elseif encoderstate = 3 then 
..... etc
endif

goto main

I'm getting desesperate to put all this together with my switches
and my reverse sequence with if then. ifelse isn't working properly (need to have oldstate stored like you told me, Olson no ?)

[HenrikOlsson]

I'm sorry, I can't keep up with you here.

Did the Select-case version not work? Is that the reason why you're now using IF and ELSEIF? And did keeping track of the previous state thru the OldState variable not work? Or why did you skip that.

If I got the sequence wrong did you try to correct it and see if the aproach I took would work or not or did you just abandon that idea because I had the reverese sequence wrong?

If the only thing controling the sequence of the commutation is the desired direction then there's no reason to keep track of the previous state because then it doesn't matter.

/Henrik.

[barneyfrance]

hello, no I did try your great ideas, the case work for the forward direction but as my elseif code the case code for the forward does not work because the second half of the commutation is the same as the previous one. So in that case I think I need to have the old case. I will keep trying experiments, thank you for your time and ideas

[barneyfrance]

The only problem i'm now having is with my reverse sequence...
I tried with select case and oldstate and it does not work I don't know why

If the only thing controling the sequence of the commutation is the desired direction then there's no reason to keep track of the previous state because then it doesn't matter.

Yep that's what I thought so for the reverse sequence I tried something like this :
If encoderstate = 62 Then
'switches ON/off
endif
IF encoderstate = 63 Then
'switchesON/off
endif
IF encoderstate = 62 Then
'switches on/off
endif


The probem is that the switches (for a same encoder state (62)) should not be the same. When I tried the above code, it is kind of like it's doing the both If..Endif at the same time which is not good.
Any more ideas ?, there's gotta be a way...
Thank you in advance..

[barneyfrance]

also, if my motor is moving forward and then suddendly i turn on switch to go backward, that won't be beautiful... I need to add some sort of security that allow to start the commutation code only if my pwm is 0 or something like that, no ?