Update with waveform sampling

diff --git a/.gitignore b/.gitignore
index e660312245d037487de9e4d9c8a8594440ee437a..7f9bfc577c3bd1447208973a8558ad653931a354 100644 (file)
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 *.cof
 *.hex
 *.obj
+*.map

diff --git a/siggen.asm b/siggen.asm
index c82975fd775a8df4367f36517765158f7cd7c746..9a9eb7980732f12ee71c60479b2b2e05598e782c 100644 (file)
--- a/siggen.asm
+++ b/siggen.asm
@@ -12,60 +12,96 @@
 .cseg
 
 .org 0x0000
-       rjmp    reset   ; RESET
+       rjmp    reset     ; RESET
        reti
-       reti            ; INT0
+       reti              ; INT0
        reti
-       reti            ; INT1
+       reti              ; INT1
        reti
-       reti            ; PCINT0
+       reti              ; PCINT0
        reti
-       reti            ; PCINT1
+       rjmp    keypress  ; PCINT1
        reti
-       reti            ; PCINT2
+       reti              ; PCINT2
        reti
-       reti            ; WDT
+       reti              ; WDT
        reti
-       reti            ; TIMER2 COMPA
+       reti              ; TIMER2 COMPA
        reti
-       reti            ; TIMER2 COMPB
+       reti              ; TIMER2 COMPB
        reti
-       reti            ; TIMER2 OVF
+       reti              ; TIMER2 OVF
        reti
-       reti            ; TIMER1 CAPT
+       reti              ; TIMER1 CAPT
        reti
-       reti            ; TIMER1 COMPA
+       reti              ; TIMER1 COMPA
        reti
-       reti            ; TIMER1 COMPB
+       reti              ; TIMER1 COMPB
        reti
-       reti            ; TIMER1 OVF
+       reti              ; TIMER1 OVF
        reti
-       reti            ; TIMER0 COMPA
+       reti              ; TIMER0 COMPA
        reti
-       reti            ; TIMER0 COMPB
+       reti              ; TIMER0 COMPB
        reti
-       reti            ; TIMER0 OVF
+       reti              ; TIMER0 OVF
        reti
-       reti            ; SPI, STC
+       reti              ; SPI, STC
        reti
-       reti            ; USART, RX
+       reti              ; USART, RX
        reti
-       reti            ; USART, UDRE
+       reti              ; USART, UDRE
        reti
-       reti            ; USART, TX
+       reti              ; USART, TX
        reti
-       reti            ; ADC
+       reti              ; ADC
        reti
-       reti            ; EE READY
+       reti              ; EE READY
        reti
-       reti            ; ANALOG COMP
+       reti              ; ANALOG COMP
        reti
-       reti            ; TWI
+       reti              ; TWI
        reti
-       reti            ; SPM READY
+       reti              ; SPM READY
        reti
 
 
+; ------------------------------------------------------------------------------
+; Registers
+
+; r0
+; r1
+; r2
+; r3
+; r4
+; r5
+; r6
+; r7
+; r8
+; r9
+; r10
+; r11
+; r12
+; r13
+; r14
+; r15
+; r16 l\_   Step size within waveform LUT (8.8 fixed point)
+; r17 h/
+; r18
+; r19
+; r20
+; r21
+; r22
+; r23 ----- Fractional part of pointer to current sample within waveform table
+; r24 ----- Second temporary
+; r25 ----- First temporary
+; r26 l\_X  (X) Pointer to current sample within waveform table
+; r27 h/
+; r28 l\_Y
+; r29 h/
+; r30 l\_Z
+; r31 h/
+
 ; ------------------------------------------------------------------------------
 ; Reset entry point
 
@@ -119,13 +155,42 @@ reset:
 
        ; ----- Set up button pin and timer for switching waveforms
 
-       ; ----- Copy the default waveform to ram
+       ; ----- Set up the initial waveform
+
+       ; Point Z at the sine table, X at the waveform table
+       ldi     XL, LOW(waveform)
+       ldi     XH, HIGH(waveform)
+       ldi     ZL, LOW(sine*2)
+       ldi     ZH, HIGH(sine*2)
+
+       ; Copy 256 bytes from program memory at Z to data at X
+       ldi     r25, 0x00
+_load_loop:
+       lpm     r24, Z+
+       st      X+, r24
+       inc     r25
+       brne    _load_loop
+
+       ; Point X at the waveform table (table must be 256-byte aligned)
+       ldi     r23, 0x00            ; Fractional part
+       ldi     XL, LOW(waveform)   ; Integer low part, must be zero
+       ldi     XH, HIGH(waveform)  ; Integer high part
+       ldi     ZL, LOW(sine*2)
+       ldi     ZH, HIGH(sine*2)
+
+       ; Initial step size
+       ldi     r16, 0x00  ; Fractional part
+       ldi     r17, 25  ; Integer part
 
        ; ----- Enable interrupts
 
        ; --------------------------------------------------------------
 loop:
-       ; Output a sample and advance
+       ; ----- Output a sample and advance
+       ld      r25, X
+       add     r23, r16  ; Fractional part
+       adc     XL, r17   ; Integer part
+       out     PORTD, r25
 
        ; ----- Read the frequency knob and adjust if necessary
 
@@ -143,7 +208,6 @@ _adc_wait:
 
        ; Read value and write to output
        lds     r25, ADCH
-       out     PORTD, r25
 
        rjmp    loop
 
@@ -170,6 +234,9 @@ keypress:
 
 .dseg
 
+; Waveform table must be 256-byte aligned
+; (The assembler appears to lack an "align" directive!)
+.org   0x100
 waveform:
        .byte   256