Writing Drivers

Comments

• kwinn Posts: 8,697

  2013-01-21 17:25 edited 2013-01-21 17:25

  Drivers for the Propeller, Windows, or some other CPU?
  
  If it's for the propeller I would suggest starting with some simple hardware like the '595 chip.
• NWCCTV Posts: 3,629

  2013-01-21 17:34 edited 2013-01-21 17:34

  I was just pondering drivers in general. I think the propeller would be a good start. What is the 595 chip and where would I start?
• Duane C. Johnson Posts: 955

  2013-01-21 18:23 edited 2013-01-21 18:23

  Wow, what a coincidence!!!
  
  I have been writing a driver for the 74HC595, 74HC4094, and 74HC4021 shift registers.
  The 595 and 4094 are serial in to 8 bit parallel out, and the 4021 is 8 bit parallel in to serial out.
  
  I'm adding a pair of instructions to Mike Greens FemtoBasic. These code snippets are written in spin:

  204: ' SROUT [<expr>] = <expr>
                   ' SROUT [<Pin#>] = <Value>
                 a := getAddress(dot)
                 outa[a..a+3] := %0000
                 dira[a..a+3] := %1110
                 b := specialExpr
                 repeat 32
                    outa[a+2] := b & 1             ' Send   a    Bit  To The Registers
                    b <-= 1                        ' Rotate Left Bits In The Variable
                    outa[a]~~                      ' Shift  Left Bits In The Registers
                    outa[a]~
                 outa[a+1]~~                       ' Strobe The Output Registers
                 outa[a+1]~
  

  205: ' SRIN [ <expr> ]
           t := getAddress(dot)
           outa[t..t+3] := %0000
           dira[t..t+3] := %1110
           i := 0
              outa[t+1]~~      ' Strobe The Registers
              outa[t+1]~
              repeat 32
                 i += ina[t+3] ' Put    a     Bit  In The Variable
                 i <-= 1       ' Rotate Left  Bits In The Variable
                 outa[t]~~     ' Shift  Left  Bits In The Registers
                 outa[t]~ 
              i += ina[t+3]    ' Put Last Bit      In The Variable
           return i
  

  This simple example expects the there are 4 chips strung in series for a total of 32 bits;
  Any combination of output or input devices can be used.
  This consumes 4 Prop pins which must be in sequence.
  1 = Shift Clock
  1+1 = Register Clock
  1+2 = Serial Bits Out
  1+3 = Serial Bits In
  
  Ok these examples are specific to FemtoBasic but the concept is sound.
  
  Enhancements:
  Allow from 1 to 4 or more chips on a set of 4 Prop pins.
  
  I am looking for a code snippet that will be the equivalent of a "ROL", Rotate Left, spin instruction that can rotate 2 to 31 bits instead of the standard 32 bits.
  
  Duane J
• NWCCTV Posts: 3,629

  2013-01-21 20:31 edited 2013-01-21 20:31

  OK, You lost me at Wow!!!!
• frank freedman Posts: 1,983

  2013-01-21 20:57 edited 2013-01-21 20:57

  Pick something in the OBEX that is not too complex and pick it apart, check out some stuff JonnyMac has posted both for methods and style.
• kwinn Posts: 8,697

  2013-01-21 21:50 edited 2013-01-21 21:50

  NWCCTV wrote: »

  OK, You lost me at Wow!!!!

  
  It really is a simple chip to start with. Only needs 3 signals to start with (plus power and ground of course), SER, SCK, and RCK. Download the data sheet and buy a '595 locally along with 8 hi efficiency leds and 8 180 to 220 ohm resistors. Connect the leds and resistors to the output pins of the '595, its SER, SCK, AND RCK pins to 2 free pins on the micro, ground the /G pin, put a pullup on the SRCLR pin and you are off to the races. I can post a block diagram if you want.