Port alias in Port Expanders (MCP23S17)

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  1. - 2nd January 2016, 20:17 #1
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    ecoli-557
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    Default Re: Port alias in Port Expanders (MCP23S17)

    Why does this not work?
    OutA.12=0 doesn't gen an error but it nor the other (OutA.15=0) turns ON an LED?????

    Code:
                          OutA=$FFFE                                        'Initial value for word var                      
                      OutA_hi=OutA.highbyte                             'Splits into hibyte
                      OutA_lo=OutA.lowbyte                              'And into low byte of the word var
'                      OutA_lo.3=0                                       'Bit mod - WORKS
'                      OutA_hi.5=0                                       'Another bit mod - WORKS
                      OutA.12=0      'Why doesn't this work?
                      OutA.15=0      'Or this?
                        OutA_MCPReg = OLATA                             'Sets up PORTA output
                        OutA_DataOut=OutA_lo                            'Sets up data to be pushed to the MCP23S17 as the low byte
                        gosub SEND_OutA_2317                            'Send it
                        pause 10                                        'Wait a bit
                        OutA_MCPReg = OLATB                             'Sets up PORTB output
                        OutA_DataOut=OutA_hi                            'Sets up data to be pushed to the MCP23S17 as the hi byte
                        gosub SEND_OutA_2317                            'Send it
    "If we knew what we were doing, it wouldn't be called research"
    - Albert Einstein
  2. - 2nd January 2016, 22:10 #2
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    Default Re: Port alias in Port Expanders (MCP23S17)

    OutA_hi=OutA.highbyte 'Splits into hibyte
    OutA_lo=OutA.lowbyte 'And into low byte of the word var
    is a simple assignment operation not an alias

    OutA=$FFFE 'Initial value for word var
    OutA.12=0
    OutA.15=0
    OutA_hi=OutA.highbyte 'Splits into hibyte
    OutA_lo=OutA.lowbyte 'And into low byte of the word var
    would fix it (get the order correct)
  3. - 2nd January 2016, 22:23 #3
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    Default Re: Port alias in Port Expanders (MCP23S17)

    Thanks!
    I tried your suggestion:
    Code:
                          OutA=$FFFF                                        'Initial value for word var                      
                      OutA.0=0                                       'Bit mod - WORKS
                      OutA.2=0                                       'Another bit mod - WORKS                      OutA.0=0                                       'Bit mod - WORKS
                      OutA.8=0                                       'Another bit mod - WORKS
                      OutA.10=0                                       'Bit mod - WORKS
                      OutA.12=0                                       'Another bit mod - WORKS
                      OutA_hi=OutA.highbyte                             'Splits into hibyte
                      OutA_lo=OutA.lowbyte                              'And into low byte of the word var
                        OutA_MCPReg = OLATA                             'Sets up PORTA output
                        OutA_DataOut=OutA_lo                            'Sets up data to be pushed to the MCP23S17 as the low byte
                        gosub SEND_OutA_2317                            'Send it
                        pause 10                                        'Wait a bit
                        OutA_MCPReg = OLATB                             'Sets up PORTB output
                        OutA_DataOut=OutA_hi                            'Sets up data to be pushed to the MCP23S17 as the hi byte
                        gosub SEND_OutA_2317                            'Send it
    And it works like a CHAMP!
    However (you knew it might come) how do I resolve a single byte variable which tells me which bit to turn on/off into a word var?
    My need for this home project, is to read a byte var and based on its value turn on/off a bit on the expander?
    Example: Var=$C, so I need to turn on the 12th bit on the expander.
    Regards,
    Steve
    "If we knew what we were doing, it wouldn't be called research"
    - Albert Einstein
  4. - 2nd January 2016, 22:33 #4
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    Default Re: Port alias in Port Expanders (MCP23S17)

    Richard-
    I tried the following:
    Code:
                          OutA=$FFFF                                        'Initial value for word var                      
                      PortDevice=$D                                     'Var from comm link
                      K=PortDevice                                      'Copes var to var for hex to dec converter
                      gosub H2D                                         'Perform sub
                      OutA.K=0     'PBP3 barks with 'Bad variable modifier
                      OutA.0=0                                          'Bit mod - WORKS
                      OutA.2=0                                          'Another bit mod - WORKS                      OutA.0=0                                       'Bit mod - WORKS
                      OutA.8=0                                          'Another bit mod - WORKS
                      OutA.10=0                                         'Bit mod - WORKS
                      OutA.12=0                                         'Another bit mod - WORKS
                      OutA_hi=OutA.highbyte                             'Splits into hibyte
                      OutA_lo=OutA.lowbyte                              'And into low byte of the word var
                        OutA_MCPReg = OLATA                             'Sets up PORTA output
                        OutA_DataOut=OutA_lo                            'Sets up data to be pushed to the MCP23S17 as the low byte
                        gosub SEND_OutA_2317                            'Send it
                        pause 10                                        'Wait a bit
                        OutA_MCPReg = OLATB                             'Sets up PORTB output
                        OutA_DataOut=OutA_hi                            'Sets up data to be pushed to the MCP23S17 as the hi byte
                        gosub SEND_OutA_2317                            'Send it
    In an effort to get from the single byte to the pointer, but PBP3 barks with the bad variable modifier.......
    There a ought to be a way to do this.......
    "If we knew what we were doing, it wouldn't be called research"
    - Albert Einstein
  5. - 2nd January 2016, 22:55 #5
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    Default Re: Port alias in Port Expanders (MCP23S17)

    OK, it is working!
    Thanks to all who helped and provided some food for thought.....
    Code below for any others who need to do this:
    Code:
                          OutA=$FFFF                                        'Initial value for word var - everything is OFF                      
                      PortDevice=$A                                     'Var from comm link
                      OutA.0[PortDevice]=0                              'This works!
'                      OutA.2=0                                          'Manual bit mod - works though  
'                      OutA.12=0                                         'Manual bit mod - works though
                      OutA_hi=OutA.highbyte                             'Splits into hibyte
                      OutA_lo=OutA.lowbyte                              'And into low byte of the word var
                        OutA_MCPReg = OLATA                             'Sets up PORTA output
                        OutA_DataOut=OutA_lo                            'Sets up data to be pushed to the MCP23S17 as the low byte
                        gosub SEND_OutA_2317                            'Send it
                        pause 10                                        'Wait a bit
                        OutA_MCPReg = OLATB                             'Sets up PORTB output
                        OutA_DataOut=OutA_hi                            'Sets up data to be pushed to the MCP23S17 as the hi byte
                        gosub SEND_OutA_2317                            'Send it
    Happy New Year!
    -Steve
    "If we knew what we were doing, it wouldn't be called research"
    - Albert Einstein
  6. - 2nd January 2016, 23:26 #6
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    Default Re: Port alias in Port Expanders (MCP23S17)

    Code:
    OutA var word


asm

OutA_hi=OutA
OutA_lo=OutA+1

endasm

OutA_hi var byte EXT
OutA_lo var byte EXT

    the easy way

    ps I hope I got the endianness correct if not swap the hi byte low byte definitions
    Last edited by richard; - 2nd January 2016 at 23:33.
  7. - 2nd January 2016, 23:53 #7
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    Default Re: Port alias in Port Expanders (MCP23S17)

    yep I did get it wrong (choice of two I will pick the wrong one every time)

    found my endianness note

    MyVar =$AABB would be stored little-endian. I.E. if the address
    of MyVar starts at 30h, then $BB will be stored at 30h followed by $AA at 31h


    so

    Code:
    asm
OutA_hi=OutA+1
OutA_lo=OutA
endasm
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