\ 2010-05-24  EW   ewlib/spi.fs
\ spi, using hw interface
\ needs in dict_appl.inc:
\   .include "words/spirw.asm"

\ words:
\     +spi   ( -- )
\     -spi   ( -- )
\     ><spi  ( x -- x' )   transfer 2 bytes

\ Needs at least these definitions
\ SPI
\ $2D constant SPCR    \ SPI Control Register
\ $2F constant SPDR    \ SPI Data Register
\ $2E constant SPSR    \ SPI Status Register

\ needs lib/bitnames.frt

\ SPCR (control register)
\ . 7 SPIE   spi interrupt enable
\ . 6 SPE    spi enable
\ . 5 DORD   data order, 0 msb first
\ . 4 MSTR   master/slave mode, 1 master
\ . 3 CPOL   clock polarity, 0 clock low on idle
\ . 2 CPHA   clock phase, 0 sample on lead. edge
\ . 01 SPIR  data rate, 00 f/4, 01 f/16,
\                       10 f/64, 11 f/128
\ SPE | MSTR | SPIR0  ==> $51

\ needs these defined before loading:
PORTB 4 portpin: /ss
\ PORTB 5 portpin: _mosi
\ PORTB 6 portpin: _miso
\ PORTB 7 portpin: _clk

: +spi ( -- )
  /ss high \ activate pullup!
  _mosi high _mosi pin_output
  _clk  low  _clk  pin_output
  \ not needed, see datasheet
  \ _miso pin_pullup_on 

  \ enable, master mode, f/128 data rate
  $53 SPCR c! 
;
: -spi  0 SPCR c! ;

\ transfer 1 byte
\ use spirw ( c -- c' )

\ transfer 1 cell
: ><spi ( x -- x' )
  dup  >< spirw
  swap    spirw
  swap >< +
;

\ fin