cleanup; switch to INT0

working with external pullup and pb0+pb2 shorted

diff --git a/foo.S b/foo.S
index 92723ec..109016d 100644 (file)
--- a/foo.S
+++ b/foo.S
@@ -1,8 +1,15 @@
+//#define DEBUG
+#define CAL_MAGIC 0x9e   // attiny4 handwired
+//#define CAL_MAGIC 0x8d  // attiny4 devboard
+//#define CAL_MAGIC 0xa7 // attiny9 devboard
+
+
 /* REGISTER NAMES */
 #define acc  r16
 #define i0   r17
 #define i1   r18
 #define i2   r19
+; XXX: move registers down!
 #define n    r21
 #define s    r22
 #define t    r23 //==Ml
@@ -36,19 +43,17 @@ TCCR0A = 0x2E
 TCCR0B = 0x2D
 TIMSK0 = 0x2B
 TIFR0  = 0x2A
-PCMSK  = 0x10
-PCIFR  = 0x11
-PCICR  = 0x12
-PRR    = 0x35
+EIMSK  = 0x13
+EICRA  = 0x15
 RAMEND = 0x5F
 FLASHM = 0x4000
 
 .section .text
 .org 0x0000 ; RESET interrupt
-       CLR     i0
        RJMP    main
-.org 0x0004 ; PCINT0 interrupt
-       CBI     PCICR, 0 ; disable interrupt
+.org 0x0002 ; INT0 interrupt
+       CBI     EIMSK, 0 ; disable interrupt
+       ;TODO: can move 1 instruction here
        RJMP    wakeup
 .org 0x0008 ; TIM0_OVF interrupt
        RJMP    sample
@@ -100,7 +105,7 @@ g: ; g(i, t) -> t
        #undef tmp
 
        LDI     Xlo, lo8(notes)
-       ADD     Xlo, t ; NOTE: notes are positioned so that hi8(notes) never changes
+       ADD     Xlo, t
        LD      t, X
 
        CLR     a2
@@ -142,7 +147,7 @@ g: ; g(i, t) -> t
                LSR a2
                ROR a1
                LSR t
-               BRCC skip6      ;sbrc t, NNN
+               BRCC skip6
                ADD a1, i0
        skip6:
                LSR a1
@@ -161,7 +166,7 @@ g: ; g(i, t) -> t
        RET
 
 main: ; setup routine
-       ; NOTE: clr i0 moved to .ord 0x0
+       CLR     i0
        CLR     i1
        CLR     i2
        CLR     acc ; we output a dummy sample before the actual first one
@@ -173,12 +178,12 @@ main: ; setup routine
        OUT     SPL, x      ; init stack ptr
        OUT     SPH, zero   ; -"-
        OUT     PUEB, zero  ; disable pullups
-       LDI     x, 0x05
-       OUT     DDRB, x     ; PORTB0:pwm, PORTB2:debug
+       LDI     x, 0x03
+       OUT     DDRB, x     ; PORTB0:pwm, PORTB1:debug (PORTB2:wakeup-input)
        LDI     x, 0xd8
        OUT     CCP, x      ; change protected ioregs
        OUT     CLKPSR, one ; clock prescaler 1/2 (4Mhz)
-       LDI     x, 0xa7     ; determined by trial-and-error (->PORTB2)
+       LDI     x, CAL_MAGIC     ; determined by trial-and-error (->PORTB1)
        OUT     OSCCAL, x   ; set oscillator calibration
        OUT     WDTCSR, zero; turn off watchdog
 
@@ -192,60 +197,61 @@ main: ; setup routine
        #undef zero
 
 loop:
-       CPI     i2, 0x78>>5 ; 16m23 -- one loop
-;TODO^: s/>>5//
+       CPI     i2, 0x78    ; 16m23 -- one loop
+;cpi i2, 1 ;TODO:removeme
        BREQ    halt
 
        SLEEP
        RJMP    loop
 
+//we use an external pullup(>= 1kohm), as line-input usually has an impedance
+//between 20-100kohm, while the attiny's internal pullups are "only" 20-50kohm
+//(which is too strong)
 halt:
+       ;stop the music, and check whether PINB0 is plugged into an audio
+       ;sink. Until then, conserve as much battery as possible.
        CLR     i2          ; clear halt condition
 
        #define zero i2
-       ; disable timer0, set all pins as input+pullup to conserve battery.
-       LDI     x, 0x08     ; disable timer clock
-       OUT     TCCR0B, x
-       ;OUT    PRR, one ; §8.3: only helps in idle and active modes
+       OUT     TCCR0A, zero   ; https://www.avrfreaks.net/forum/oc1a-state-during-pwm-disable
+       OUT     TCCR0B, zero   ; disable timer to free audio pin for wakeup function
 
+       ;TODO: both of these necessary?
+       SBI     PORTB, 0    ; assert high level on pin2, so we can detect a plugged-in state as a low level.
+       SBI     PORTB, 2    ; assert high level on pin2, so we can detect a plugged-in state as a low level.
 
-sbi PORTB, 0 ; force pin high, so pcint triggers on connect to ground --- XXX TODO: this does not work reliably for PORTB0
-sbi PORTB, 2 ; force pin high, so pcint triggers on connect to ground (works reliably for portb2)
+       OUT     DDRB, zero  ; set all pins as input
+       ;;;OUT  PUEB, zero     ; disable pullups on all pins (already done @ init/main)
 
-
-       OUT     DDRB, zero
-       LDI     x, 0x0f
-       OUT     PUEB, x
-
-
-
-       SBI     PCMSK, 2    ; listen for pin change on the audio out pin (i.e. wake up when a audio sink is connected)
-;TODO^: s/2/0/
-       OUT     PCICR, one  ; enable PCINT0
+       ;set up INT0 to wake up when a audio sink is connected
+       SBI     EIMSK, 0     ; set-bit-0 high => enable interrupt
+       OUT     EICRA, zero  ; logical low generates INT0
 
        ;enter power-down-mode
        LDI     x, 0x05     ; sleep mode: power-down, enabled
        OUT     SMCR, x
        SLEEP
-       OUT     SMCR, one   ; sleep mode: idle, enabled
+       ;OUT    SMCR, one   ; sleep mode: idle, enabled
+       OUT     SMCR, zero  ; sleep mode: disabled
 
        RJMP loop
 
 wakeup:
-       SBI     PCIFR, 0 ; clear interrupt
-       OUT     PUEB, zero ; remove pullups
-       LDI     x, 0x05 ; restore output pins
+       ;;;SBI  PCIFR, 1    ; clear interrupt (handled by reti)
+       ;;;OUT  PUEB, zero  ; remove pullups (already in main)
+       LDI     x, 0x03     ; restore output pins
        OUT     DDRB, x
-       ;OUT    PRR, zero ; reenable periphials
+       LDI     x, 0x81
+       OUT     TCCR0A, x   ; reenable COMA bits
        LDI     x, 0x09
-       OUT     TCCR0B, x ; reenable timer0
+       OUT     TCCR0B, x   ; reenable timer0
        RETI
        #undef zero
 
 sample:
        OUT     OCR0AL, acc ; start by outputting a sample, because routine has variable runtime
 #ifdef DEBUG
-       SBI     PORTB, 2 ; to measure runtime
+       SBI     PORTB, 1 ; to measure runtime
 #endif // DEBUG
 
        MOV     n, i2
@@ -377,7 +383,7 @@ sample:
        SBCI    i2, -1
 
 #ifdef DEBUG
-       CBI     PORTB, 2   ; end runtime measurement
+       CBI     PORTB, 1   ; end runtime measurement
 #endif // DEBUG
        OUT     TIFR0, one ; clear pending interrupt (routine takes two intr.cycles)
        RETI ; reenables interrupts