Shiftout (SPI) and I2C issues

Rex Heyer · 2010-05-30 03:15

Thanks in advance for any help.

I am simply trying to get any serial communication going (not counting the standard asynchronous method) . I am using SX/B for the compiler and have tried generating basic SPI and I2C output. The weird thing is that I have attached the outputs to an oscilloscope and the chips only output occasional voltage spikes...no data. Please review the very basic software routines and let me know if I am missing anything.

R>

Zoot · 2010-05-31 14:58

Looks like they should work. I would move the bulk of the program to a "Main" label so that start isn't always used, e.g.


Start:
  TRIS_LEDs = %00000000


Main:

  DO
    FOR i = 0 to 255
        SHIFTOUT Dpin, Cpin, LSBFIRST, i
            LEDs = i    
        PAUSE 1000                     
    NEXT
  LOOP

But that shouldn't matter too much in this case. I would expect to see data on your 'scope....

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T&E Engineer · 2010-06-01 16:42

Your missing the Latch signal which occurs after the SHIFTOUT.

' -------------------------------------------------------------------------
' Device Settings
' -------------------------------------------------------------------------
DEVICE   SX28, OSC4MHZ, TURBO, STACKX, OPTIONX
FREQ   4_000_000
ID   "SHIFTOUT"
' -------------------------------------------------------------------------
' IO Pins
' -------------------------------------------------------------------------
Dpin   PIN  RA.0 OUTPUT ' shift data
Cpin   PIN  RA.1 OUTPUT ' shift clock
 
[b]Lpin   PIN  RA.2 OUTPUT ' latch it[/b]

LEDs            VAR     RB
TRIS_LEDs       VAR     TRIS_B
' -------------------------------------------------------------------------
' Variables
' -------------------------------------------------------------------------
tmpB1   VAR  Byte
i  VAR Byte
' =========================================================================
 PROGRAM Start
' =========================================================================
Start:
  TRIS_LEDs = %00000000
  DO
    FOR i = 0 to 255
     SHIFTOUT Dpin, Cpin, LSBFIRST, i
            LEDs = i 
     PAUSE 1000   
 
     [b]Pulsout Lpin, 1[/b]
   
    NEXT
  LOOP

Shiftout (SPI) and I2C issues

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