Multiple Pulsin Measurements

[FinchPJ]

Does anyone have any experience of multiple PULSIN measurements - ie simultaneous on more than one pin - obviously would need to sample for a full sample period - 65535 cycles to be sure no pulses received on any other pin even if received on one pin. Also would need to handle a partially measured (ie ongoing beyond the sample period) pulse. So I am thinking of a full port pulse sample, result to an word array (Period[7]), where Period[n] = 0 if no pulse, 65535 if an incomplete pulse and a result otherwise. I am planning to write if no one has done already - any interest?

[FinchPJ]

OK - I have written a PicBasic routine to do mPULSIN - a bit slow as you would expect, but works

            for i = 0 to 7 : Period[i] = 0 : next
            pCount = 65535                  ' PULSIN_MAX
            k = Mask
cycle0:     j = mPort & k                   'Port AND Mask
            for i = 0 to 7
                if (j & dcd i) = dcd i then 'Bit i set - Pulse found
                    Period[i] = Period[i] + 1
                else                        'Pulse ended or no pulse
                    if Period[i] >0 then    'Already received a pulse
                        k = k & (~dcd i)    'Clear i'th bit in mask
                    endif
                endif
            next
            if k = 0 then return
            pCount = pCount - 1
            if pCount <> 0 then cycle0
            return

I have also written in assembler but need to test before posting....
Peter

[FinchPJ]

OK - here it is in Assembler - disappointingly not that much faster!

'**** mPULSIN defines ***
Period  var word[7]
mPort   var PortB
Mask    con %00000011   'Mask of port pins to check
i       var byte
j       var byte
k       var byte
pCount  var word
sample  var byte
CALL mPULSIN
END

asm
_mPULSIN:   CLRF    _Period         ;Period[0] = 0
            CLRF    _Period + 1
            CLRF    _Period + 2     ;Period[1] = 0
            CLRF    _Period + 3
            CLRF    _Period + 4     ;Period[2] = 0
            CLRF    _Period + 5
            CLRF    _Period + 6     ;Period[3] = 0
            CLRF    _Period + 7
            CLRF    _Period + 8     ;Period[4] = 0
            CLRF    _Period + 9
            CLRF    _Period + 10    ;Period[5] = 0
            CLRF    _Period + 11
            CLRF    _Period + 12    ;Period[6] = 0
            CLRF    _Period + 13
            CLRF    _Period + 14    ;Period[7] = 0
            CLRF    _Period + 15
            
            MOVLW   0xFF
            MOVWF   _pCount  
            MOVLW   0x0F 
            MOVWF   _pCount + 1 ;pCount = $FFF  = 4095
            MOVLW   _Mask
            MOVWF   _k          ;k = Mask
            CLRF    _sample     ;clear sample flag
            
cycle:      MOVF    _mPort, W   ;Sample the Port
            ANDWF   _k, W
            MOVWF   _j          ;j = Port AND Mask
            
B0:         BTFSS   _j,0        ;Bit set? Pulse high
            GOTO    B0Clear
            BSF     _sample,0   ;flag that now sampling
            INCFSZ  _Period     ;Period[0] = Period[0] + 1
            GOTO    B1
            INCF    _Period + 1
            GOTO    B1
B0Clear:    BTFSS   _sample,0   ;Pulse low - already sampling?
            GOTO    B1
            BCF     _k,0        ;Clear Bit in Mask
B1:         BTFSS   _j,1        ;Bit set? Pulse high
            GOTO    B1Clear
            BSF     _sample,1   ;flag that now sampling
            INCFSZ  _Period + 2 ;Period[1] = Period[1] + 1
            GOTO    B2
            INCF    _Period + 3
            GOTO    B2
B1Clear:    BTFSS   _sample,1   ;Pulse low - already sampling?
            GOTO    B2
            BCF     _k,1        ;Clear Bit in Mask
B2:         BTFSS   _j,2        ;Bit set? Pulse high
            GOTO    B2Clear
            BSF     _sample,2   ;flag that now sampling
            INCFSZ  _Period + 4 ;Period[2] = Period[2] + 1
            GOTO    B3
            INCF    _Period + 5
            GOTO    B3
B2Clear:    BTFSS   _sample,2   ;Pulse low - already sampling?
            GOTO    B3
            BCF     _k,2        ;Clear Bit in Mask
            
B3:         BTFSS   _j,3        ;Bit set? Pulse high
            GOTO    B3Clear
            BSF     _sample,3   ;flag that now sampling
            INCFSZ  _Period + 6 ;Period[3] = Period[3] + 1
            GOTO    B4
            INCF    _Period + 7
            GOTO    B4
B3Clear:    BTFSS   _sample,3   ;Pulse low - already sampling?
            GOTO    B4
            BCF     _k,3        ;Clear Bit in Mask
          
B4:         BTFSS   _j,4        ;Bit set? Pulse high
            GOTO    B4Clear
            BSF     _sample,4   ;flag that now sampling
            INCFSZ  _Period + 8 ;Period[4] = Period[4] + 1
            GOTO    B5
            INCF    _Period + 9
            GOTO    B5
B4Clear:    BTFSS   _sample,4   ;Pulse low - already sampling?
            GOTO    B5
            BCF     _k,4        ;Clear Bit in Mask
B5:         BTFSS   _j,5        ;Bit set? Pulse high
            GOTO    B5Clear
            BSF     _sample,5   ;flag that now sampling
            INCFSZ  _Period + 10 ;Period[5] = Period[5] + 1
            GOTO    B6
            INCF    _Period + 11
            GOTO    B6
B5Clear:    BTFSS   _sample,5   ;Pulse low - already sampling?
            GOTO    B6
            BCF     _k,5        ;Clear Bit in Mask
B6:         BTFSS   _j,6        ;Bit set? Pulse high
            GOTO    B6Clear
            BSF     _sample,6   ;flag that now sampling
            INCFSZ  _Period + 12 ;Period[6] = Period[6] + 1
            GOTO    B7
            INCF    _Period + 13
            GOTO    B7
B6Clear:    BTFSS   _sample,6   ;Pulse low - already sampling?
            GOTO    B7
            BCF     _k,6        ;Clear Bit in Mask
B7:         BTFSS   _j,7        ;Bit set? Pulse high
            GOTO    B7Clear
            BSF     _sample,7   ;flag that now sampling
            INCFSZ  _Period + 14 ;Period[7] = Period[7] + 1
            GOTO    Next
            INCF    _Period + 15
            GOTO    Next
B7Clear:    BTFSS   _sample,7   ;Pulse low - already sampling?
            GOTO    Next
            BCF     _k,7        ;Clear Bit in Mask
Next:       MOVF    _k, F       ;Is Mask = 0?
            BTFSC   STATUS,Z    ;Branch on No Zero
            RETURN              ;Finished all samples
            DECFSZ  _pCount
            GOTO    cycle
            DECFSZ  _pCount + 1
            GOTO    cycle
            RETURN              ;pCount reached 0 - Timeout
ENDASM

[Charles Linquis]

Can't you use the gated timers or interrupts to do what you want?

[rmteo]

Can't you use the gated timers or interrupts to do what you want?

That would be too easy.

[FinchPJ]

I need to make 8 simultaneous (relatively) measurements of pulsewidth on 8 different input pins - is there a PIC that could handle this with timers or interrrupts?

[cncmachineguy]

Can we get just a little more info about the pulses? for instance are you trying for a Logic storage type thing or reading R/C Rx pulses. Both need to have 8 bits read, but the Logic storage needs to get the states and go back watching while the Rx has at least 2mS before the next pulses may show up. Do you have an anticipated max/min pulse width?

[cncmachineguy]

Also can you expand on the first was "slow"? Do you mean it was to slow to react to the pulses? were they accurate but offset? How much percision and resolution do you need?