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/*
* Funcgen firmware
* Signal timer
*
* Copyright (C) 2007-2009 Michael Buesch <m@bues.ch>
*
* 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.
*/
#include "timer.h"
#include "util.h"
#include "main.h"
#include <avr/io.h>
#include <avr/interrupt.h>
extern const uint8_t PROGMEM table_sine[];
extern const uint8_t PROGMEM table_triang[];
/* Lookup table for the active waveform (if used).
* The array is _guaranteed_ to be at SRAM address 0x100.
* This allows some optimizations in the lowlevel generator.
*/
static uint8_t active_generator_table[256] __attribute__((section(".generatortab")));
/* We abuse some I/O registers for some core generator state variables,
* because an in/out is faster than an lds/sts.
* So doing I/O to an MMIO location is twice as fast as accessing SRAM.
* Of course, we need to select the I/O registers _carefully_ so the sideeffects
* don't bite us.
*/
/* The function pointer to the active generator. */
#define R_GENERATOR_FUNC_PTR_LO UBRRL
#define R_GENERATOR_FUNC_PTR_HI TWBR
/* The generator statemachine counter. */
#define R_GENERATOR_STATE TWAR
/* The generator statemachine increment step. */
#define R_GENERATOR_STEP OSCCAL
/* Storage for the saved SREG in the ISR. */
#define R_SAVED_SREG MCUCR
ISR(TIMER1_COMPA_vect) __naked;
ISR(TIMER1_COMPA_vect)
{
__asm__ __volatile__(
" ; Generator interrupt handler \n"
" push r30 \n"
" push r31 \n"
" in r30, __SREG__ \n"
" out %[_SAVED_SREG], r30 \n"
" in r30, %[_GEN_FUNC_LO] \n"
" in r31, %[_GEN_FUNC_HI] \n"
" ijmp ; Jump to the real handler \n"
: /* none */
: [_GEN_FUNC_LO] "M" (_SFR_IO_ADDR(R_GENERATOR_FUNC_PTR_LO))
, [_GEN_FUNC_HI] "M" (_SFR_IO_ADDR(R_GENERATOR_FUNC_PTR_HI))
, [_SAVED_SREG] "M" (_SFR_IO_ADDR(R_SAVED_SREG))
);
}
#define GENERATOR_EPILOGUE \
" ; Generator epilogue (start) \n"\
" in r30, %[_SAVED_SREG] \n"\
" out __SREG__, r30 \n"\
" pop r31 \n"\
" pop r30 \n"\
" reti \n"\
" ; Generator epilogue (end) \n"
/* Generic table based signal generator */
static void __naked __used generator_generic_table(void)
{
/* The signal table is at SRAM address 0x100, so we can efficiently
* use the generator_state as index into the table. */
__asm__ __volatile__(
" in r31, %[_GEN_STEP] \n"
" in r30, %[_GEN_STATE] \n"
" add r30, r31 \n"
" out %[_GEN_STATE], r30 \n"
" ldi r31, 0x01 \n"
" ld r31, Z \n"
" out %[_DAC_PORT], r31 \n"
GENERATOR_EPILOGUE
: /* none */
: [_DAC_PORT] "M" (_SFR_IO_ADDR(DAC_PORT))
, [_GEN_STATE] "M" (_SFR_IO_ADDR(R_GENERATOR_STATE))
, [_GEN_STEP] "M" (_SFR_IO_ADDR(R_GENERATOR_STEP))
, [_SAVED_SREG] "M" (_SFR_IO_ADDR(R_SAVED_SREG))
: "memory"
);
}
/* Square signal generator */
static void __naked __used generator_square(void)
{
__asm__ __volatile__(
" in r30, %[_GEN_STATE] \n"
" in r31, %[_GEN_STEP] \n"
" add r30, r31 \n"
" out %[_GEN_STATE], r30 \n"
" clr r31 \n"
" cpi r30, 0x7F \n"
" brlo low \n"
" com r31 /* high */ \n"
" low: \n"
" out %[_DAC_PORT], r31 \n"
GENERATOR_EPILOGUE
: /* none */
: [_DAC_PORT] "M" (_SFR_IO_ADDR(DAC_PORT))
, [_GEN_STATE] "M" (_SFR_IO_ADDR(R_GENERATOR_STATE))
, [_GEN_STEP] "M" (_SFR_IO_ADDR(R_GENERATOR_STEP))
, [_SAVED_SREG] "M" (_SFR_IO_ADDR(R_SAVED_SREG))
: "memory"
);
}
/* Sawtooth signal generator */
static void __naked __used generator_sawt(void)
{
__asm__ __volatile__(
" in r30, %[_GEN_STATE] \n"
" in r31, %[_GEN_STEP] \n"
" add r30, r31 \n"
" out %[_GEN_STATE], r30 \n"
" out %[_DAC_PORT], r30 \n"
GENERATOR_EPILOGUE
: /* none */
: [_DAC_PORT] "M" (_SFR_IO_ADDR(DAC_PORT))
, [_GEN_STATE] "M" (_SFR_IO_ADDR(R_GENERATOR_STATE))
, [_GEN_STEP] "M" (_SFR_IO_ADDR(R_GENERATOR_STEP))
, [_SAVED_SREG] "M" (_SFR_IO_ADDR(R_SAVED_SREG))
: "memory"
);
}
/* Update the hardware prescaler, based on the software selection. */
static void prescaler_update(uint16_t prescaler)
{
uint16_t cr;
cr = TCCR1B & ~((1 << CS10) | (1 << CS11) | (1 << CS12));
switch (prescaler) {
case PRESCALER_1:
cr |= (1 << CS10) | (0 << CS11) | (0 << CS12);
break;
case PRESCALER_8:
cr |= (0 << CS10) | (1 << CS11) | (0 << CS12);
break;
case PRESCALER_64:
cr |= (1 << CS10) | (1 << CS11) | (0 << CS12);
break;
case PRESCALER_256:
cr |= (0 << CS10) | (0 << CS11) | (1 << CS12);
break;
case PRESCALER_1024:
cr |= (1 << CS10) | (0 << CS11) | (1 << CS12);
break;
default:
BUG_ON(1);
}
TCCR1B = cr;
}
static inline void set_generator_function(void (*func)(void))
{
R_GENERATOR_FUNC_PTR_LO = (uint16_t)func;
R_GENERATOR_FUNC_PTR_HI = ((uint16_t)func) >> 8;
}
void generator_reconfigure(uint8_t waveform, uint16_t ocr,
uint16_t prescaler, uint8_t step)
{
uint8_t sreg;
sreg = irq_disable_save();
switch (waveform) {
case WAV_SINE:
memcpy_P(active_generator_table, table_sine, sizeof(active_generator_table));
set_generator_function(generator_generic_table);
break;
case WAV_SQUARE:
set_generator_function(generator_square);
break;
case WAV_TRIANG:
memcpy_P(active_generator_table, table_triang, sizeof(active_generator_table));
set_generator_function(generator_generic_table);
break;
case WAV_SAWT:
set_generator_function(generator_sawt);
break;
default:
BUG_ON(1);
}
R_GENERATOR_STEP = step;
R_GENERATOR_STATE = 0;
prescaler_update(prescaler);
OCR1A = ocr;
irq_restore(sreg);
}
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