12f675_fuse_about_to_blow!

[LEDave]

Hi mackrackit,

Not sure I have a strong point...

Hey, you put up with me, so patience is one of them

And don't forget it was trying to turn an LED on using ASM that after a near breakdown put me onto PBP

I'll go onto MATCH & DECODE tomorrow, slowly getting there (slowly).

Dave

[LEDave]

It still doesn't take much to stump me I'm afraid........

 MATCH = MATCH + 1        ' We have a match so increment match count
    IF MATCH = 2 THEN DECODE ' Everything matched twice, we're good
    GOTO Main                ' Else do it all over

When the Timer was set up for a 65ms reset we had:

MATCH = 0           ' Clear match count

Then the SYNCH_BYTE & DATA etc arrived and everything was good giving:

MATCH = MATCH + 1        ' We have a match so increment match count

So to my mind that makes MATCH = 0 +1 ie 1.

But then we have:

 IF MATCH = 2 THEN DECODE ' Everything matched twice, we're good

So either the data arrives twice within the 65ms time period to move onto DECODE or my understanding of MATCH = MATCH + 1 is wrong.

Help!

Dave

[mackrackit]

So either the data arrives twice within the 65ms time period to move onto DECODE or my understanding of MATCH = MATCH + 1 is wrong.

Not within the 65ms but just twice. MATCH does not get set to zero until DECODE is reached.
One good set of data could arrive then many not-goods, then one more good THEN DECODE.

Being this came from Bruce it is hard for me to question it but....
Here is what I think it should be

    ' Test new checksum against one received in CHK_SUM
    IF CheckSum != CHK_SUM THEN MAIN ' Failed checksum, return
    MATCH = MATCH + 1        ' We have a match so increment match count

    ' Test data bytes for match
    IF (DAT_IN1) != (DAT_IN2) THEN MAIN ' Failed data comparison, return
    MATCH = MATCH + 1        ' We have a match so increment match count

    IF MATCH = 2 THEN DECODE ' Everything matched twice, we're good
    GOTO Main                ' Else do it all over

[LEDave]

Far more intuitive for a newbie your way mackrackit. I would have been stuck in a loop looking for a second MATCH until my watchdog timer kicked in (that's not to say Bruce's program isn't pure genius from where I'm sitting).

I'm thinking that if one MATCH had occurred but was followed by bad data, then the ASM :

clrf   MATCH         ; Clear match variable

would reset the single MATCH to zero after 65ms?

Onto DECODE then.

Dave

[LEDave]

  ' hardware init
    PORTA = 0
    TRISA = %00111001   ' RA1 and RA2 are LED outputs

So PORTA.1-2 are outputs

And BYTES received will be

%10101011 or %10101101

PORTA = DAT_IN1 & %00000110

The manual says:Bitwise Operators: & %00000001 ' Isolate bit 0 of BYTE.

So I'm thinking: & %00000110 ' Isolate bits 1 & 2, would give:

%00000010 from %10101011 & %00000100 from %10101101 as PORTA, depending on which button was pressed and light the LED's.

Hot, cold or tepid?

Dave

[mackrackit]

Hot, cold or tepid?

Hot
Looks like you got it.

BTW, I missed

clrf   MATCH         ; Clear match variable

So the original code would have to receive two good with out a bad. I wonder why Bruce did it that way?

[LEDave]

Cheers mackrackit

So the original code would have to receive two good with out a bad. I wonder why Bruce did it that way?

I don't know.....

One thing though, from Bruce's code (and please bear in mind this is the thinking of a newbie here).The only way(as I see it) that MATCH can ever reach a count of two and then move onto 'DECODE' is for the program to run from 'SERIN2' all the way to 'GOTO Main' once and then a second time to 'IF MATCH = 2 THEN DECODE' for MATCH to ever equal 2. Am I missing something here?

' Wait for Synch byte, then get new inbound data & checksum
    SERIN2 D_IN,N2400,[WAIT(Synch),DAT_IN1,DAT_IN2,CHK_SUM,TEST]
    
    T1CON.0 = 0    ' Stop Timer1 once we've received data
    TMR1L = 0      ' Clear low byte
    TMR1H = 0      ' Clear high byte
    
    ' / **** Begin data validation **** /
    
    ' Calculate checksum by adding 2 data bytes together
    CheckSum = DAT_IN1 + DAT_IN2
    
    ' Test new checksum against one received in CHK_SUM
    IF CheckSum != CHK_SUM THEN MAIN ' Failed checksum, return
    
    ' Test data bytes for match
    IF (DAT_IN1) != (DAT_IN2) THEN MAIN ' Failed data comparison, return
    
    MATCH = MATCH + 1        ' We have a match so increment match count
    IF MATCH = 2 THEN DECODE ' Everything matched twice, we're good
    GOTO Main                ' Else do it all over

Dave