How to display dot on 7-seg , 4 digit


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  1. #1
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    [QUOTE=chai98a;30011]Hi paul borgmeier
    Now I try to show temp with DS1820 on 7 seg 4 digit
    Below is code , I can read data temp from ds1820 and send to RS232 -->OK but canot to diplay to 7 Seg. Ex 29.5C

    How to show number , dot and character on display ??

    Code :
    Define LOADER_USED 1
    DEFINE OSC 4
    @ Device pic16F877, xt_OSC, BOD_OFF, PWRT_ON, WDT_OFF, PROTECT_OFF,WRT_ON

    Segments Var PORTC
    Digits Var PORTD

    i Var Byte
    n Var Byte
    Value Var Word


    TRISc = $00 ' Set segment pins to output
    TRISd = $f0 ' Set digit pins to output


    ' Allocate variables
    command var byte ' Storage for command
    J var byte ' Storage for loop counter
    temp var word ' Storage for temperature
    DQ var PORTd.4 ' Alias DS1820 data pin
    DQ_DIR var TRISd.4 ' Alias DS1820 data direction pin

    TRISc = $00 ' Set segment pins to output
    TRISd = $f0 ' Set digit pins to output
    TrisB = $00
    Portb = $00
    OPTION_REG = $55 ' Set TMR0 configuration 1:64
    INTCON = $A0 ' Enable TMR0 interrupts
    On Interrupt Goto display

    ADCON1 = 7 ' Set PORTA and PORTE to digital

    ' Lcdout $fe, 1, "Temp in degrees C" ' Display sign-on message
    'debug ====
    DEFINE HSER_RCSTA 90h
    DEFINE HSER_TXSTA 24h
    DEFINE HSER_SPBRG 12 ' 19200 Bauds ,4 m
    'debug ====

    ' Mainloop to read the temperature and display on LCD
    mainloop:
    Gosub init1820 ' Init the DS1820

    command = $cc ' Issue Skip ROM command
    Gosub write1820

    command = $44 ' Start temperature conversion
    Gosub write1820

    Pause 2000 ' Wait 2 seconds for conversion to complete

    Gosub init1820 ' Do another init

    command = $cc ' Issue Skip ROM command
    Gosub write1820

    command = $be ' Read the temperature
    Gosub write1820
    Gosub read1820

    'Display the decimal temperature
    'Lcdout $fe, 1, dec (temp >> 1), ".", dec (temp.0 * 5), " degrees C"
    'HSEROUT ["Temp = ",dec (temp>>1),".", dec (temp.0*5)," C",13,10]
    Goto mainloop ' Do it forever


    ' Initialize DS1820 and check for presence
    init1820:
    Low DQ ' Set the data pin low to init
    Pauseus 500 ' Wait > 480us
    DQ_DIR = 1 ' Release data pin (set to input for high)

    Pauseus 100 ' Wait > 60us
    If DQ = 1 Then
    'Lcdout $fe, 1, "DS1820 not present"
    Pause 500
    Goto mainloop ' Try again
    Endif
    Pauseus 400 ' Wait for end of presence pulse
    Return


    ' Write "command" byte to the DS1820
    write1820:
    For j = 1 to 8 ' 8 bits to a byte
    If command.0 = 0 Then
    Gosub write0 ' Write a 0 bit
    Else
    Gosub write1 ' Write a 1 bit
    Endif
    command = command >> 1 ' Shift to next bit
    Next j
    Return

    ' Write a 0 bit to the DS1820
    write0:
    Low DQ
    Pauseus 60 ' Low for > 60us for 0
    DQ_DIR = 1 ' Release data pin (set to input for high)
    Return

    ' Write a 1 bit to the DS1820
    write1:
    Low DQ ' Low for < 15us for 1
    @ nop ' Delay 1us at 4MHz
    DQ_DIR = 1 ' Release data pin (set to input for high)
    Pauseus 60 ' Use up rest of time slot
    Return


    ' Read temperature from the DS1820
    read1820:
    For J = 1 to 16 ' 16 bits to a word
    temp = temp >> 1 ' Shift down bits
    Gosub readbit ' Get the bit to the top of temp
    Next J
    Return

    ' Read a bit from the DS1820
    readbit:
    temp.15 = 1 ' Preset read bit to 1
    Low DQ ' Start the time slot
    @ nop ' Delay 1us at 4MHz
    DQ_DIR = 1 ' Release data pin (set to input for high)
    If DQ = 0 Then
    temp.15 = 0 ' Set bit to 0
    Endif
    Pauseus 60 ' Wait out rest of time slot
    Return

    '================== 7 seg ment display ==============================
    disable
    display:
    INTCON.2 = 0 'clear the interrupt flag

    VALUE = (temp >>1)+(temp.0 * 5)

    For i = 0 To 3 ' Loop through 4 digits
    n = Value Dig i ' Get digit to display
    Gosub display1 ' Display the value
    NEXT I

    goto mainloop

    display1:
    Digits = $ff ' All digits off to prevent ghosting

    ' Convert binary number in n to segments for LED
    ' COM ANODE 1234567890
    Lookup n, [$3F,$06, $5B, $4F, $66, $6D, $7D, $07, $7F, $6F, $77, $7C, $39, $5E, $79, $71], Segments
    ' Set digit pin i to 0 (on) and the rest of the pins to 1 (off)

    Digits = ~Dcd i

    Return
    enable
    End

  2. #2
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    I see - the PNPs (which I did not know about) threw me off. It appears proper for Common Anode.

    Try this:
    1) On your buffer, tie 1 and 19 low so they do not float.
    2) The 3rd from last line of your code - change "Return" to "Resume" (See manual section on On Interrupt for details).

    Please report back progress so that others following this can get closure.

    EDIT:
    3) Your lookup values need to be inverted - as written they are for common cathode displays. Change to ($C0, $F9, $A4, etc) where the segments you want off are high and the segments you want on are low.
    4) To turn on the decimal point on the second digit, insert right after the lookup table
    if i = 1 then Segments.7 = 0 (or if the DP is always to be on you could do this in hardware by disconnecting RC7 from D7 on U2 and connecting RD1 to D7 on U2 (in addition to RD1 going to the Base of Q2))
    Last edited by paul borgmeier; - 26th December 2006 at 07:15. Reason: add more info
    Paul Borgmeier
    Salt Lake City, UT
    USA
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  3. #3
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    Here is the full list of Common Cathode:

    Starting from 0 to 9.

    $c0, $F9, $A4, $B0, $99, $92, $82, $F8, $80, $90



    ------------------------------
    "If the Earth were a single state, Istanbul would be its capital." Napoleon Bonaparte

  4. #4
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    Sayzer,
    You bolded Common Cathode as if it is for sure - you must mean Common Anode. Common Cathode requires the segment to be high to be on while Common Anode requires Segments to be low to be on. His buffer is non-inverting. (Your set looks correct though - I left a little for the OP to work out as a learning exercise but now he is close to set).

    EDIT:
    Oh, for thoroughness, have you considered testing DT's suggested gif animator at 1/4 scale?
    Last edited by paul borgmeier; - 26th December 2006 at 19:35.
    Paul Borgmeier
    Salt Lake City, UT
    USA
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  5. #5
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    Hi Paul,

    My set is for Common Cathode.
    I now see what you meant.

    Let me check for Common Anode...Should be somewhere in my HDDs.

    BTW; I am just testing the animator and will remove it now. I think is is slowing down the CPU when there is more then one running.

    -----------------
    "If the Earth were a single state, Istanbul would be its capital." Napoleon Bonaparte

  6. #6
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    Sayzer,

    You have it correct for Common Anode in post #10 (at least the first three are correct - I didn't check your others). The OP should be grateful for your help because you probably saved him hours of work and frustration)

    Best Wishes
    Paul Borgmeier
    Salt Lake City, UT
    USA
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  7. #7
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    Paul,

    Ok, here is the clarification.
    (from 0 to 9)

    Common Anode : $c0, $F9, $A4, $B0, $99, $92, $82, $F8, $80, $90

    Common Cathode : $3F, $06, $5B, $4F, $66, $6D, $7D, $07, $7F, $6F


    Using Dot or not changes from set to set.
    These are what I use.




    ----------------------------
    "If the Earth were a single state, Istanbul would be its capital." Napoleon Bonaparte

  8. #8
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    Hi paul borgmeier
    I'm not understand for item 1
    1) On your buffer, tie 1 and 19 low so they do not float.

    For item 4 , as you advise with modify some hard were right, Do you have other way with out modify hard or not.

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