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|
;;
;; spreadspace pic utils
;;
;;
;; Copyright (C) 2011-2013 Christian Pointner <equinox@spreadspace.org>
;;
;; This file is part of spreadspace pic utils.
;;
;; spreadspace pic utils is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; any later version.
;;
;; spreadspace pic utils is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with spreadspace pic utils. If not, see <http://www.gnu.org/licenses/>.
;;
;; --- transmit byte and add it to csum
com_tx_byte
movlb .4
movwf SSP1BUF
movlb .0
bcf INTPIN
xorwf csum,f
movlb .4
com_tx_byte_wait1
btfss SSPSTAT,BF
goto com_tx_byte_wait1
movf SSP1BUF,w
movlb .0
bsf INTPIN
com_tx_byte_wait2 ; also wait for SS to go up again
btfss PORTB,5 ; this lowers the risk for raise conditions
goto com_tx_byte_wait2 ; with next byte (INT pin)
return
;; ---- wait for byte to be received
com_rx_byte
movlb .4
btfsc SSP1STAT,BF
goto com_rx_got_byte
btfss SSP1CON1,SSPOV
goto com_rx_byte
movf SSP1BUF,w
bcf SSP1CON1,SSPOV
goto com_rx_byte
com_rx_got_byte
movf SSP1BUF,w
movlb .0
return
;; ----- initialize com (this is called by bootmacro, it's not a subroutine - no return at the end)
com_init
movlb .3
bcf ANSELB,ANSB1 ; SDI as digital input
bcf ANSELB,ANSB4 ; SCK as digital input
movlb .1
movlw b'01110000' ; set internal OSC to 8MHz
movwf OSCCON
bcf TRISB,2 ; RB2(SDO) = out
bcf INTPIN ; interrupt line to master
movlb .4
movlw b'01000000' ; SMP=0,CKE=1
movwf SSP1STAT
movlw b'00100100' ; SSPEN=1,CKP=0,SSPM=0100(SPI Slave with SS)
movwf SSP1CON1
bcf SSP1CON3,BOEN
movlb .0
bsf INTPIN
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