max7219 interface with BS1 debuging assist

nick bernard

i have a small pcb with a max7219 and 4 7 seg displays. its works just fine w/ a bs2p via the 3 wire serial interface (shifting)

if i hook it up to a bs1 running a simple routine the max7219 does not respond to any commands
also the shifting routine on the bs1 works fine with a tpic6a596 shift register in another applicaion of mine.
i just modified it to shift 2 bytes and latch.

here's the code and schematic where R9 = 68k

anyhelp?

nickB

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League Bowling.... it's not a sport, it's a way of life

Jon Williams

The MAX7219 is expecting bits MSBFIRST, so the following [noparse][[/noparse]partial] example should get you going:

SYMBOL  shftDat = B0         ' byte for MAX7219
SYMBOL  shftMSB = BIT7       ' MSB of shftDat
 
 
' put byte for MAX7219 into "shftDat"
 
 
SHIFT_OUT_MSB:
  FOR idx = 0 TO 7           ' shift eight bits
    Dpin = shftMSB           ' put bit on data pin
    PULSOUT Cpin, 1          ' clock the bit
    shftDat = shftDat * 2    ' shift bits left
  NEXT
  RETURN

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Jon Williams
Applications Engineer, Parallax
Dallas Office

nick bernard

HAIL JON

thx for the help

i got it now... also i had to throw in a dirs line in there too

ROX ON
nickB

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League Bowling.... it's not a sport, it's a way of life

Jon Williams

Yep, you have to do that -- sorry I forgot to mention it -- as

Dpin = shftMSB

is like saying

OUTx = some_bit_value

If the pin has not been made an output then there will be no change of state on it.

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Jon Williams
Applications Engineer, Parallax
Dallas Office