Is it possible to interpret non-standard serial data with PicBasic (sample attached)

[Heckler]

This, to me, is the classic problem of how to tell (program) your micro controller to recognize and interpret the pattern.
The human brain combined with an eyeball can recognize it... now you just need to figure out how to translate that into code.

I would start by watching for the start pulse, which is longer than the other pulses. Then keep track of the width of the following pulses (or the width of the "low" part. Then watch for one or more extended "low" pulses.

Since you only need to differentiate between 0 and any other number/key press, then just watch for an extended "low" in a given time period after the extended "high" start pulse. If in the given time period you do not get any extended "low" pulses then the digit is "0" other wise if you get an extended "low" pulse then the keypress was non-zero.

Since the quantity of pulses in each character is always 34 then you should be able to just set up a counter to increment whenever the pulse is low and stop incrementing when the pulse goes back high. Then if the counter has incremented above a certain threshold then that particular "low" pulse was a "wide" one and indicates a non zero digit. (I hope that makes sense)

I believe it is easily do-able. you just need to distill it down to how to detect the extended low pulse that indicates a non-zero digit pressed.

that is how I would attack the challenge.

[pedja089]

Code for that is in post #11 except it waits for transition from low to high to start measure 34 low intervals.

[CuriousOne]

Yes, I know how to implement detection logically, I have no issues with algorithm, but I can't implement it in hardware, also, I can't understand, why statement
IF PORTC.4=1

or

IF PORTC.4=0

makes corresponding pin high or low?

[tumbleweed]

IF PORTC.4=1
or
IF PORTC.4=0

makes corresponding pin high or low?

I highly doubt that. I don't know how you're testing it, but if that's the case things are seriously broken.

You likely have some other issue.

[HenrikOlsson]

The IF statement per se should not and I'm pretty sure does not twiddle the pin but if what you you're doing is somehing like...

If PortC.4 = 0 THEN
   PortC.1 = 1
ENDIF

...and there happens to be analog functions on the pins which you haven't disabled then the actual state of PortC.4 isn't read correctly and you're getting into the classic RMW issue where the "invalid" state of PortC.4 is being written back to PortC.4 when the write operation to PortC.1 occurs but without seeing the rest of the code it's hard to say for sure.

/Henrik.

[CuriousOne]

Here is the complete code:

Include "modedefs.bas"  ' Include serial modes
   TRISA = %11111111       ' Set PORTA to all input
       TRISC = %00000000	    ' Sets all PortB pins to output
   ADCON1 = %10000101      ' Set PORTA analog and right justify result
   ADCON0=%00000000
   low portc.4
   low portc.5
   
X   VAR PORTC.4 

DEFINE LCD_DREG PORTB
DEFINE LCD_DBIT 4
DEFINE LCD_RSREG PORTB
DEFINE LCD_RSBIT 0
DEFINE LCD_EREG PORTB
DEFINE LCD_EBIT 1
DEFINE LCD_BITS 4 
DEFINE LCD_LINES 2
DEFINE LCD_COMMANDUS 1500
DEFINE LCD_DATAUS 44
DEFINE OSC 4

lcdout "test 2"
PAUSE 500

LABEL VAR WORD
DROEBITI VAR WORD


taki:
if portc.4=0 then
COUNT PORTC.4, 60, LABEL
endif
if label=0 then
goto taki
endif
LCDOUT $FE,$c0, DEC(LABEL), "          "
GOTO TAKI

I have source of signal (chip with name grinded off, but holtek logo is recognizable), which is connected directly to PORTC.4. Also, scope is connected to same pin.

As long as I introduce the statement "if portc.4=0 then"
If it is "=0" then pin is sunk to ground, so no pulses can be detected, and nothing can be seen on scope. If it is "=1", then pin gets driven high, and no pulses can be seen with scope or read too.

Chip is 16F870.

[pedja089]

 TRISA = %11111111       ' Set PORTA to all input
   TRISC = %00000000	    ' Sets all PortB pins to output
   ADCON1 = %10000101      ' Set PORTA analog and right justify result
   ADCON0=%00000000
   low portc.4
   low portc.5

Is there something strange here?

[richard]

for comparison I came up with this , oddly it uses mode code space

'****************************************************************
'*  Name    : deMODULATOR.BAS                                   *
'*  Author  : richard                                           *
'*  Notice  : Copyright (c) 2016                                *
'*          : All Rights Reserved                               *
'*  Date    : 5/29/2016                                         *
'*  Version : 1.0                                               *
'*  Notes   : decodes missing pulse encoded data stream A.5     *
'*          : 16F1825                                           *
'****************************************************************
  #CONFIG
             __config        _CONFIG1,    _FOSC_INTOSC & _CP_OFF & _WDTE_ON  &  _PWRTE_ON  &  _MCLRE_ON  & _CLKOUTEN_OFF
              __config      _CONFIG2, _PLLEN_ON & _LVP_OFF            
#ENDCONFIG
 
OSCCON=$70 
DEFINE OSC 32



'                       PIC 16F1825



    TRISA     = %111110	 ' Make somepins Input 
    trisc     = %111100  ;Make some pins Input   
    ANSELA=0     
    ANSELC=0
    led var latc.0      ;DEBUG
    led2 var latc.1      ;DEBUG
    demod var porta.5     ;demod in
    X VAR byte
    darta   VAR byte[4] 
    counter var word
    dm_state   VAR byte
    lata.0=1             ;DEBUG
    clear
    led=0
    DEFINE DEBUG_REG PORTA
    DEFINE DEBUG_BIT 0       
    DEFINE DEBUG_BAUD 9600
    DEFINE DEBUG_MODE 0     
    pause 2000
    Debug "Start",13 ,10  
    DEFINE PULSIN_MAX 9000

main:
    select case dm_state
        case 0
            PULSIN demod, 0, counter
            if counter > 7800  then
                dm_state=1
                x=0
            endif
        case 1
            pir1.1=0 
            tmr2=0
            t2con=7
            while demod : wend
            if   pir1.1 | (tmr2 < 220)   then
               dm_state=0
            else
                dm_state=2
                tmr2=0
            endif
        case 2
            while !demod : wend
            t2con=0
            if   pir1.1 then 
             dm_state=0
             led=1 
            endif 
            if tmr2 < 150    then 
                darta.0[x]=0
            else
                darta.0[x]=1
            endif
            tmr2=0
            x=x+1
            if x >31 then 
                dm_state=3
            else
                while demod : wend
                t2con=7    
            endif
        case 3
            led2=1     ;DEBUG
        '    Debug 13 ,10 ,hex2 darta[3] ,hex2 darta[2],hex2 darta[1],hex2 darta[0]    ;DEBUG
            Debug 13 ,10 ,bin8 darta[3],bin8 darta[2],bin8 darta[1],bin8 darta[0]    ;DEBUG
            pause 200
            led2=0             ;DEBUG
            dm_state=0
    end select

goto main

[CuriousOne]

the 1ms was just test, I used it to check MCU speed, whenever OSCCON and DEFINE OSC were correct, later it was removed.

I have Henrik's code running, I connect it to actual hardware, and width of large pulse, which should be 9000us, measured only 600 ?