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The FAQ about RWS-374-1

ASK RECEIVER Receiving Software and Improves

    reply this question lin (2006/7/8)
    Question:

    Introduction:

    There are common TIME phase transpose problem for Super-Regenerative
    receivers. It is easily causes decode end of software can not decode
    due to distance (near or far) if the software works according to FSK
    way.


    So, in general, mostly the proportion expression encode will be
    use in ASK low cost encoders, such as HT-12E or the IC of PIC series.
    In this article, we take HT-12E for example to avoid the data missing
    problem of receiver modules RWS-374 or RWS-371 series. Seeing the source
    of HT-12E first: more than 20 years ago, it was AMD CHIP use on RF remote
    controller all over the world.


    It uses modulation and carrier frequency,
    adjusting and turning into 1 12KHZ and 8KHz to tell 1 and 0 signals.
    In this way, it can save the signal adjust of RF end, directly input
    to DECODER end after RF wave checking then produce by TI, as same as
    the encode way of HT-12E. OSC is RC, RC is the PLUG-IN, it draws low
    of decode IC price.


    After 3 years, HOLTEK places C into the CHIP and
    produce HT-12E. HT-12E makes RF remote controllers in popular price
    until now.


    Wave analysis:

    As follows, there is 13BIT in HT-12E wave form. 1BIT always is 1 (1.0
    signal); 2~9BIT usually use for ADDRESS or ID; 10~13BIT are controlling
    BIT. While the 1BIT signal is 0, the wave form will be the gray part.



    As the graphs above, can find out the output of ASK DATA will have
    different TIME based on the distance. Therefore, in the part of
    software, have to take 1BIT to cont it. After cont 1BIT, divide it by
    2 and then add 1BIT.


    Then take CONT2 = CONT + (CONT/2) compare with
    the following BIT. If the following BIT is bigger than CONT2, then DATA=0;
    if it is smaller than CONT2, then DATA=1.


    It can all be decode by this
    way, no matter the differences of distance or phase. Sample program
    as below, it can decode by CALL T assistant program. When it is 0 that
    RETEL reacts, represents there will be no signal.


    When it is 1 that
    RETEL reacts, represents have signal incomes, it is quite convenient
    to use.



    ORG 0X00
    ;*******************************
    ;****** 1999 12 17 ***********
    ;****** mt_1.asm ***********
    ; LIN FU WEN
    ;*******************************
    RTCC EQU 0X01
    PC EQU 0X02
    R3 EQU 0X03
    RA EQU 0X05
    RB EQU 0X06
    RC EQU 0X07
    CODE EQU 0X11
    CODE1 EQU 0X12
    CODE2 EQU 0X13
    CODE3 EQU 0X14
    FLAG EQU 0X15
    FLAG1 EQU 0X16
    FLAG2 EQU 0X17
    TFLAG EQU 0X18
    INST EQU 0X19
    FHIN EQU 0X1A
    CONT EQU 0X1B
    CONT1 EQU 0X1C
    CONT2 EQU 0X1D
    CONT3 EQU 0X1E
    CONT4 EQU 0X1F
    CONT5 EQU 0X20
    CONT6 EQU 0X21
    CONT7 EQU 0X22
    CONT8 EQU 0X23
    CONT9 EQU 0X24
    TEMP EQU 0X25
    ;FLAG2,4 IS RB5 RESTE FALG 0=REBS 1=UNREBS
    ;FLAG2,0 IS VT FLAG IF 0 IN 1 IS NOT
    JMP MAIN
    ORG 0X08
    JMP INT1 int1
    ; *********************
    ; *** DECODER ***
    ; *********************
    T:
    NOP
    CLR CONT1
    CLR CONT3
    T11:
    CLR CONT
    CLR CONT2
    T2:
    JBC RA,3
    CLR CONT
    MOV A,@0XF0
    SUB A,RTCC
    JBS R3,0
    JMP T2
    CLR RTCC
    INC CONT
    MOV A,@0X18 ;24 IS MAX
    SUB A,CONT
    JBC R3,0
    JMP T3
    JZ CONT1
    JMP T2
    RETL @0X00
    T3:
    CLR CONT
    T31:
    JBC RA,3
    JMP T4
    MOV A,@0XF0
    SUB A,RTCC
    JBS R3,0
    JMP T31
    CLR RTCC
    JZ CONT1
    JMP T31
    RETL 000H
    T4:
    JBS RA,3
    JMP T45
    JZ CONT
    JMP T4
    JMP T2
    T45:
    JBS CONT2,4
    JMP T5
    MOV A,CONT
    SUB A,TEMP
    JBC CONT2,3
    JMP T41
    JBS R3,0
    JMP T42
    RRC CODE2
    JBS R3,0
    CLR CONT3
    JMP T43
    T42:
    RRC CODE2
    JBC R3,0
    CLR CONT3
    JMP T43
    T41:
    JBS R3,0
    JMP T44
    RRC CODE3
    JBS R3,0
    CLR CONT3
    JMP T43
    T44:
    RRC CODE3
    JBC R3,0
    CLR CONT3
    T43:
    INC CONT2
    MOV A,@0X1C
    SUB A,CONT2
    JBS R3,0
    JMP T3
    SWAP CODE3
    MOV A,@0X0F
    AND CODE3,A ;9999
    INC CONT3
    MOV A,@0X03
    SUB A,CONT3
    JBS R3,0
    JMP T11
    RETL @0X01
    T5:
    BS CONT2,4
    MOV A,CONT
    MOV TEMP,A ;99999
    BC R3,0
    RRCA CONT
    ADD TEMP,A
    JMP T3
    ;*******************************
    ;* *
    ;* MAIN PROGRAM *
    ;* *
    ;*******************************
    MAIN:
    MOV A,@0X08
    IOW RA
    CLR RA
    MOV A,@0XC0
    IOW RB
    CLR RB
    MOV A,@0X0C
    CONTW
    CLR CONT2
    CLR FLAG2
    BS RB,3
    CLR TFLAG
    CLR R3
    DISI
    MOV A,@0XF8
    IOW 0X0B
    MOV A,@0X3F ;RB6,7 PULL HI
    IOW 0X0D ;KEY RB PULL HI
    WEN:
    WENC:
    WDTC
    JBS RB,6
    JMP SET
    CALL T
    AND A,@0X01
    JBC R3,2
    JMP WEN
    MOV A,CODE
    SUB A,CODE2
    JBC R3,2
    JMP OPEN
    CLR CODE
    JMP WEN
    OPEN:
    ;****** DECODER IS OK ******
    ;
    JMP WEN
    ;-----------------------------
    ; ORG 1FFH
    ; JMP MAIN
    ;---------------------------

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