IR decode problem "hitachi TV remote"

[dhouston]

I'm not sure what you are asking but here's a code snippet that captures the 4 bytes represented by the Hitachi (same as NEC) code.

IR	VAR	byte[4]
pulses  VAR     byte[33]
BitMask VAR     byte
i       VAR     byte            'loop index
b       VAR     byte            'byte index
LeadIn  VAR     word            'start pulse


loop:   PulsIn GPIO.1, 0, LeadIn
        If LeadIn < 855 Then loop
   	If LeadIn > 1045 Then loop
   	For i = 0 TO 32
     	  PulsIn GPIO.1, 1, pulses[i]
   	Next
        For i = 1 To 32
          If (pulses[i] < 40) Or (pulses[i] > 200) Then 
            Goto loop
          EndIf
          b = i >> 3                      	'0,1,2,3
          If pulses[i] > 99 Then  
            IR[b] = IR[b] | BitMask       	'set bit 
          EndIf 
          BitMask = BitMask << 1        	'$01,$02,$04,$08,$10,$20,$40,$80
          If BitMask = 0 Then BitMask = $01 
        Next

At this point IR[0:3] contain the data.

[chai98a]

Hi dhouston thank for your advise.
After we try on your code that show improvement of pulse capture ability but still not canisistance.

Question. Refer code above.
Why my code show low speed than your code?
For my code show 4-5 value of pulse capture but your code can capture all bit.

Do you have tips for make basic source code or not...

[dhouston]

I wrote that from memory and made one mistake. The first capture in the loop is the space following the start pulse. The bits of the code are in pulses[1:32].

The second loop should be changed to:

        For i = 0 To 31
          If (pulses[i+1] < 40) Or (pulses[i+1] > 200) Then 
            Goto loop
          EndIf
          b = i >> 3                      	'0,1,2,3
          If pulses[i+1] > 99 Then  
            IR[b] = IR[b] | BitMask       	'set bit 
          EndIf 
          BitMask = BitMask << 1        	'$01,$02,$04,$08,$10,$20,$40,$80
          If BitMask = 0 Then BitMask = $01 
        Next

I've used that basic algorithm for several years to capture X-10 RF codes which also use the NEC protocol. You can find a description of the protocol at http://www.cpcares.com/pdf/UPD6121G-001.PDF.

If you're having a problem with consistency, it is most likely hardware related.

With IR, you should also define a maximum value for PulsIn. That's not always needed with RF where there are constant noise pulses in the absence of a signal.