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;
; Atmel Mega8 based ODIN chipset
;
; Copyright (c) 2009 Michael Buesch <mb@bu3sch.de>
;
; This program 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 2
; of the License, or (at your option) any later version.
;
; This program 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.
.listmac
.include "m8def.inc"
.def zero = r0 ; Always zero'd (constant value)
.def one = r1 ; Always one (constant value)
.def two = r2 ; Always two (constant value)
.def three = r3 ; Always three (constant value)
.def sigin = r4 ; Input signal
.def t0 = r16 ; Temp reg 0
.def t1 = r17 ; Temp reg 1
.def t2 = r18 ; Temp reg 2
.def t3 = r19 ; Temp reg 3
.def steptab_start = r22 ; Step table start marker (constant value)
.def steptab_center = r23 ; Step table center marker (constant value)
.def steptab_end = r24 ; Step table end marker (constant value)
.def directions = r25 ; LMD dir pin states in bit0/1
.equ DAC_PORT = PORTD
.equ DIROUT_PORT = PORTB
.equ DIROUT_LMD1_BIT = 0
.equ DIROUT_LMD2_BIT = 1
.equ IN_PIN = PINC
.equ IN_CLK_BIT = 0
.equ IN_DIR_BIT = 1
.dseg
; Allocate enough space for 60 microsteps.
; Align to 0x100 so that the high byte of the pointer will
; never change.
.org 0x100
MEM_STEPTABLE: .byte (60 * 2)
; Direction pin helper macros.
; The two direction pins can be seen as a two bit gray code number.
; So we convert to binary, increment/decrement and convert back to gray.
; We convert to binary/gray by flipping the lower bit, if the upper bit is set.
;
; The gray code sequence is
; gray | binary
; 00 | 00
; 01 | 01
; 11 | 10
; 10 | 11
;
.macro dir_increment
sbrc directions, 1 ; Convert to binary number
eor directions, one ;
inc directions ; Increment ...
andi directions, 3 ; ... and mask the number.
sbrc directions, 1 ; Convert to gray code
eor directions, one ;
.endm
.macro dir_decrement
sbrc directions, 1 ; Convert to binary number
eor directions, one ;
dec directions ; Decrement ...
andi directions, 3 ; ... and mask the number.
sbrc directions, 1 ; Convert to gray code
eor directions, one ;
.endm
; A big delay used for debouncing the switches on the debug-board.
.macro debug_delay
.ifdef DEBUG
push t0
push t1
ldi t0, 0xFF
l1:
ldi t1, 0xFF
l2:
dec t1
brne l2
dec t0
brne l1
pop t1
pop t0
.endif
.endm
.cseg
.org 0x000
rjmp reset
.org 0x026
;*******************************************
;*** ENTRY POINT ***
;*******************************************
reset:
cli
clr zero
clr one
inc one
mov two, one
inc two
mov three, two
inc three
; Init the stackpointer
ldi t0, low(RAMEND)
out SPL, t0
ldi t0, high(RAMEND)
out SPH, t0
; Setup the port configuration
ldi t0, 0xFF ; B=out
out DDRB, t0
ldi t0, 0x00
out PORTB, t0
ldi t0, 0x00 ; C=in
out DDRC, t0
ldi t0, 0xFF ; C=pullups
out PORTC, t0
ldi t0, 0xFF ; D=out
out DDRD, t0
ldi t0, 0x00
out PORTD, t0
; Copy the step table to RAM
ldi t0, (NR_STEPS * 2)
ldi ZL, low(steptable * 2)
ldi ZH, high(steptable * 2)
ldi XL, low(MEM_STEPTABLE)
ldi XH, high(MEM_STEPTABLE)
copy: lpm t1, Z+
st X+, t1
dec t0
brne copy
; Init the status registers
ldi XL, low(MEM_STEPTABLE) ; X is the table pointer
ldi XH, high(MEM_STEPTABLE) ; High byte is constant
ldi directions, 0
ldi steptab_start, low(MEM_STEPTABLE)
ldi steptab_center, low(MEM_STEPTABLE) + NR_STEPS
ldi steptab_end, low(MEM_STEPTABLE) + NR_STEPS * 2 - 1
; Initially set the outputs and enter the mainloop
ld t0, X
out DIROUT_PORT, directions
out DAC_PORT, t0
rjmp mainloop
;*******************************************
;*** MAINLOOP ***
;*******************************************
mainloop:
sbic IN_PIN, IN_CLK_BIT ; Wait for falling edge
rjmp mainloop
debug_delay
wait_rising:
in sigin, IN_PIN ; Get the input signals
sbrs sigin, IN_CLK_BIT ; Wait for rising edge
rjmp wait_rising
; Test the direction bit to decide whether we move forward or backward
sbrs sigin, IN_DIR_BIT
rjmp backward
; *** Forward move ***
cp XL, steptab_start ; If we're at the table start ...
breq fwd1
cpse XL, steptab_center ; ... or at the table center ...
rjmp fwd2
fwd1: dir_increment ; ... increment the LMD direction state
fwd2: cp XL, steptab_end ; Increment the table pointer
breq fwd3
inc XL
rjmp fwd4
fwd3: mov XL, steptab_start
fwd4: out DIROUT_PORT, directions ; Commit LMD dir state, if not done, yet
ld t0, X
out DAC_PORT, t0 ; Commit the LMD DAC state
rjmp mainloop
backward:
; *** Backward move ***
out DIROUT_PORT, directions ; Commit LMD dir state, if not done, yet
cp XL, steptab_start ; Decrement the table pointer
breq bwd1
dec XL
rjmp bwd2
bwd1: mov XL, steptab_end
bwd2: cp XL, steptab_start ; If we're at the table start ...
breq bwd3
cpse XL, steptab_center ; ... or at the table center ...
rjmp bwd4
bwd3: dir_decrement ; ... decrement the LMD direction state
bwd4: ld t0, X
out DAC_PORT, t0 ; Commit the LMD DAC state
rjmp mainloop
.include "tables.S"
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