Max7219 and a DS1620

Nick Waldvogel

How can I get the max7219 to display the temp on a 3 digit display? I am using a DS1620 as a temp prob and I have it sending out on a Pink but for some reason I can't seem to figure out how to properly display it this way! Thanks for your time!! I love learning this stuff!!

Chris Savage

Nick,

·· Here is a project that uses the DS1620 and the MAX7219...Between the two you should be able to come up with enough examples to do what you want.

http://forums.parallax.com/showthread.php?p=552892

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Nick Waldvogel

Thank you so very much for your info, Chris!! It has gotten me much closer to where I want to be. As of right now I have the display showing info but it's in binary.... A little more info about this is that I have 5 segments and the last two are set up to display the temp symbol. I know it's got to be so simple but I can't seem to be able to figure it out and have been beating my head for several days over it!! LOL Thanks for the info!

' Hardware interface with the 7219:
DATA_n  CON  7  ' Bits are shifted out this pin # to 7219.
CLK     CON  5  ' Data valid on rising edge of this clock pin.
Load    CON  6  ' Tells 7219 to transfer data to LEDs.

decode   CON  9                         ' Decode register; a 1 turns on BCD decoding.
brite    CON  10                          ' "       "   " intensity register.
scan     CON  11                           ' "       "   " scan-limit register.
switch   CON  12                         ' "       "   " on/off register.
Test     CON  15                        ' Display Test Mode


XX    VAR Byte                          'General purpose variable, byte.
DegF  VAR Byte                          'Variable for Deg F.
DegC  VAR Byte                          'Variable for Deg C
max_dat  VAR  Word                      ' Word to be sent to MAX7219.
index   VAR  Nib                        ' Index into setup table.
temp  VAR  Nib                          ' Temporary variable used in outputting digits.
nonZ  VAR  Bit                          ' Flag used in blanking leading zeros.
d7219           VAR     Word            ' Data For MAX7219
DegF0 VAR    DegF.BIT0
DegF1 VAR    DegF.BIT1
DegF2 VAR    DegF.BIT2

odd  VAR  index.BIT0                    ' Lsb of index.


'Note: DS1620 has to be preprogramed for mode 2.

FOR index = 0 TO 7                      ' Retrieve 8 items from table.
  LOOKUP index,[noparse][[/noparse]scan,4,brite,1,decode,$1F,switch,1],max_dat
  SHIFTOUT DATA_n,CLK,MSBFIRST,[noparse][[/noparse]max_dat]
  IF odd = 0  THEN noLoad               ' If odd is 1, pulse Load line.
  PULSOUT Load,1
NoLoad:                                 ' Else, don't pulse.
NEXT                                    ' Get next item from table.

HIGH 13                                 'Select the DS1620.
SHIFTOUT 15, 14, LSBFIRST, [noparse][[/noparse]238]        'Send the "Start Conversions" command.
LOW 13                                  'Do the command.

'------- Main---------

DO                                      'Going to display every 1 sec.

  HIGH 13                               'Select the DS1620
  SHIFTOUT 15, 14, LSBFIRST, [noparse][[/noparse]170]      'Send the "Get Data" command.
  SHIFTIN 15,14,LSBPRE, [noparse][[/noparse]xx]             'Get the data.
  LOW 13                                'End the command.

  DegC = xx / 2

  DegF = DegC * 9 / 5 + 32              'Convert data.

  DEBUG HOME
   DEBUG "The Temp is ",DEC DegF,32,"Degrees", CR

  GOSUB Show_Temp

LOOP





Show_Temp:

  index = 1
  d7219 = 8
  GOSUB Show_Max_Temp

  index = 2
  d7219 = 8
  GOSUB Show_Max_Temp

  index = 3
  d7219 = DegF0
  GOSUB Show_Max_Temp

  index = 4
  d7219 = DegF1
  GOSUB Show_Max_Temp

  index = 5
  d7219 = DegF2
  GOSUB Show_Max_Temp


  RETURN

Show_Max_Temp:
  SHIFTOUT DATA_n,CLK, MSBFIRST, [noparse][[/noparse]index, d7219]
  PULSOUT Load,5                    ' Latch Data
  RETURN

Chris Savage

You can use the DIG operator to extract individual digits from the variable with the Temperature (DegF?).

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Chris Savage
Parallax Tech Support
csavage@parallax.com

Nick Waldvogel

Thanks again Chris!!! After reading the text about DIG, it makes sense. I will give it a try in the morning. It's 11:30 here and the lady friend wants to go to bed.....