IR decode problem "hitachi TV remote"

[chai98a]

I have to try decode IR hitachi TV format but not work pls advise

We used pulsin for measure pulse with.
1. we measure head pulse and next pluse bit and keep it .
2. bring pulse bit to decode "0" or "1"
3. Prind data tp pc

Problem :
The decode pulse with not consitance not show all same time after we push in the same key on remote.

Hitachi =32 bit ,see attached picture
head +8800 -2200
Bit "0" +550 -1650
Bit "1" +550 -550




Here is my code:

'PIC 16F877

DEFINE LOADER_USED 1
DEFINE OSC 4

DEFINE HSER_RCSTA 90h
DEFINE HSER_TXSTA 24h
DEFINE HSER_SPBRG 12 ' 19200 Bauds

Header Var Word ' Header pulse length
Packet Var Word ' 16-bit IR information
Packet1 Var Word ' 16-bit IR information
P_Val Var Byte[32] ' Record pluse width
IR_But Var Byte ' The BUTTON code returned
IR_Dev Var Byte ' The DEVICE code returned
Sony_LP Var Byte ' Temporary loop variable
Green_LED Var Portb.3 ' Assign the red LED to this pin

TRISA = 0
LOW Green_LED

START:

GOSUB IRIN
IF IR_But =255 THEN start 'HIGH Green_LED

For Sony_Lp=0 to 23 ' Do 12-bits
Pulsin PortB.0,0,P_Val[SONY_LP] ' Receive the IR bit pulse
HSEROUT ["B ",DEC P_VAL[SONY_LP],13,10]
NEXT
HSEROUT ["Bottom ",DEC IR_But,13,10]
HSEROUT ["Comand ",DEC IR_Dev,13,10]

Packet =0
Packet1 =1
intcon.1=0
GOTO START

IRIN:
IR_Dev=255:IR_But=255
Pulsin PortB.0,0,Header ' Measure the header length.
'HSEROUT ["H ",DEC Header,13,10]
If Header < 792 then Return ' Verify a good header
If Header > 968 then Return ' If not valid then exit

For Sony_Lp=0 to 23 ' Do command 8-bits
Pulsin PortB.0,1,P_Val[SONY_LP] ' Receive the IR bit pulse "0"

NEXT

For Sony_Lp=0 to 7 ' Do device 8-bits
If P_Val[SONY_LP] >= 120 then ' If it's >= 120 then we've received a 1
Packet.0[Sony_Lp] = 1 ' So set the appropriate bit of PACKET
Else
Packet.0[Sony_Lp] = 0
Endif
NEXT

For Sony_Lp=17 to 24 ' Do 12-bits
If P_Val[SONY_LP] >= 120 then ' If it's >= 120 then we've received a 1
Packet1.0[Sony_Lp] = 1 ' So set the appropriate bit of PACKET1
Else
Packet1.0[Sony_Lp] = 0
Endif
NEXT

' Split the 7-bit BUTTON code, and the 5-bit DEVICE code

'IR_But=Packet & %01111111 ' Mask the 7 BUTTON bits
IR_But=Packet
'IR_Dev=(Packet >>7) & %00011111 ' Move down and mask, the 5 DEVICE bits
IR_dEV=Packet1

Return

[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.