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DmxSimpleMod.cpp
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DmxSimpleMod.cpp
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/**
* DmxSimple - A simple interface to DMX.
*
* Modified by Matt Mets for WS2822 LED programming
*
* Copyright (c) 2008-2009 Peter Knight, Tinker.it! All rights reserved.
*/
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <Arduino.h>
#include "DmxSimpleMod.h"
#define DMX_MODE_DISABLED 0 // Disable DMX output
#define DMX_MODE_CONTINUOUS 1 // Send the DMX data continuosly
#define DMX_MODE_SINGLE_SHOT 2 // Send the DMX frame one, then stop
volatile uint8_t dmxBuffer[DMX_SIZE];
uint16_t dmxMax = 16; // Number of DMX channels to transmit
uint8_t dmxMode = DMX_MODE_DISABLED; // Transmission mode
uint16_t dmxState = 0; // Transmission state: 0:start byte, >0: sending channel
uint8_t dmxPin = 3; // Arduino pin to output DMX to
volatile uint8_t *dmxPort; //
uint8_t dmxBit = 0; //
void dmxBegin();
void dmxEnd();
void dmxSendByte(volatile uint8_t);
void dmxWrite(int,uint8_t);
void dmxMaxChannel(int);
/* TIMERn has a different register mapping on the ATmega8.
* The modern chips (168, 328P, 1280) use identical mappings.
*/
#if defined(__AVR_ATmega168__) || defined(__AVR_ATmega168P__) || defined(__AVR_ATmega328P__) || defined(__AVR_ATmega1280__)
#define TIMERn_INTERRUPT_ENABLE() TIMSK2 |= _BV(TOIE2)
#define TIMERn_INTERRUPT_DISABLE() TIMSK2 &= ~_BV(TOIE2)
#define TIMERn_OVF_vect TIMER2_OVF_vect
#elif defined(__AVR_ATmega8__)
#define TIMERn_INTERRUPT_ENABLE() TIMSK |= _BV(TOIE2)
#define TIMERn_INTERRUPT_DISABLE() TIMSK &= ~_BV(TOIE2)
#define TIMERn_OVF_vect TIMER2_OVF_vect
#elif defined(__AVR_ATmega32U4__)
#define TIMERn_INTERRUPT_ENABLE() TIMSK4 |= _BV(TOIE4)
#define TIMERn_INTERRUPT_DISABLE() TIMSK4 &= ~_BV(TOIE4)
#define TIMERn_OVF_vect TIMER4_OVF_vect
#else
#define TIMERn_INTERRUPT_ENABLE()
#define TIMERn_INTERRUPT_DISABLE()
#define TIMERn_OVF_vect
/* Produce an appropriate message to aid error reporting on nonstandard
* platforms such as Teensy.
*/
#error "DmxSimple does not support this CPU"
#endif
// Initialise the DMX engine
inline void dmxBegin()
{
dmxMode = DMX_MODE_CONTINUOUS;
dmxState = 0;
// Set up port pointers for interrupt routine
dmxPort = portOutputRegister(digitalPinToPort(dmxPin));
dmxBit = digitalPinToBitMask(dmxPin);
// Set DMX pin to output
pinMode(dmxPin,OUTPUT);
// Initialise DMX frame interrupt
//
// Presume Arduino has already set Timer2 to 64 prescaler,
// Phase correct PWM mode
// So the overflow triggers every 64*510 clock cycles
// Which is 510 DMX bit periods at 16MHz,
// 255 DMX bit periods at 8MHz,
// 637 DMX bit periods at 20MHz
TIMERn_INTERRUPT_ENABLE();
}
// Stop the DMX engine
// Turns off the DMX interrupt routine
inline void dmxEnd()
{
TIMERn_INTERRUPT_DISABLE();
dmxMode = DMX_MODE_DISABLED;
}
// Transmit a complete DMX byte
// We have no serial port for DMX, so everything is timed using an exact
// number of instruction cycles.
//
// Really suggest you don't touch this function.
void dmxSendByte(volatile uint8_t value)
{
uint8_t bitCount, delCount;
__asm__ volatile (
"cli\n"
"ld __tmp_reg__,%a[dmxPort]\n"
"and __tmp_reg__,%[outMask]\n"
"st %a[dmxPort],__tmp_reg__\n"
"ldi %[bitCount],11\n" // 11 bit intervals per transmitted byte
"rjmp bitLoop%=\n" // Delay 2 clock cycles.
"bitLoop%=:\n"\
"ldi %[delCount],%[delCountVal]\n"
"delLoop%=:\n"
"nop\n"
"dec %[delCount]\n"
"brne delLoop%=\n"
"ld __tmp_reg__,%a[dmxPort]\n"
"and __tmp_reg__,%[outMask]\n"
"sec\n"
"ror %[value]\n"
"brcc sendzero%=\n"
"or __tmp_reg__,%[outBit]\n"
"sendzero%=:\n"
"st %a[dmxPort],__tmp_reg__\n"
"dec %[bitCount]\n"
"brne bitLoop%=\n"
"sei\n"
:
[bitCount] "=&d" (bitCount),
[delCount] "=&d" (delCount)
:
[dmxPort] "e" (dmxPort),
[outMask] "r" (~dmxBit),
[outBit] "r" (dmxBit),
[delCountVal] "M" (F_CPU/1000000-3),
[value] "r" (value)
);
}
// DmxSimple interrupt routine
// Transmit a chunk of DMX signal every timer overflow event.
//
// The full DMX transmission takes too long, but some aspects of DMX timing
// are flexible. This routine chunks the DMX signal, only sending as much as
// it's time budget will allow.
//
// This interrupt routine runs with interrupts enabled most of the time.
// With extremely heavy interrupt loads, it could conceivably interrupt its
// own routine, so the TIMERn interrupt is disabled for the duration of
// the service routine.
ISR(TIMERn_OVF_vect,ISR_NOBLOCK) {
// Prevent this interrupt running recursively
TIMERn_INTERRUPT_DISABLE();
uint16_t bitsLeft = F_CPU / 31372; // DMX Bit periods per timer tick
bitsLeft >>=2; // 25% CPU usage
while (1) {
if (dmxState == 0) {
// Next thing to send is reset pulse and start code
// which takes 35 bit periods
uint8_t i;
if (bitsLeft < 35) break;
bitsLeft-=35;
*dmxPort &= ~dmxBit;
for (i=0; i<11; i++) _delay_us(8);
*dmxPort |= dmxBit;
_delay_us(8);
dmxSendByte(0);
} else {
// Now send a channel which takes 11 bit periods
if (bitsLeft < 11) break;
bitsLeft-=11;
dmxSendByte(dmxBuffer[dmxState-1]);
}
// Successfully completed that stage - move state machine forward
dmxState++;
if (dmxState > dmxMax) {
dmxState = 0; // Send next frame
// If we aren't in continuous transmission mode, stop.
if(dmxMode != DMX_MODE_CONTINUOUS) {
dmxEnd();
}
break;
}
}
// Enable interrupts for the next transmission chunk
TIMERn_INTERRUPT_ENABLE();
}
void dmxWrite(int channel, uint8_t value) {
if ((channel > 0) && (channel <= DMX_SIZE)) {
if (value<0) value=0;
if (value>255) value=255;
dmxMax = max((unsigned)channel, dmxMax);
dmxBuffer[channel-1] = value;
}
}
void dmxMaxChannel(int channel) {
dmxMax = min(channel, DMX_SIZE);
}
void DmxSimpleClass::usePin(uint8_t pin) {
dmxPin = pin;
// TODO: configure pin output mode here?
}
void DmxSimpleClass::maxChannel(int channel) {
dmxMaxChannel(channel);
}
void DmxSimpleClass::write(int address, uint8_t value)
{
dmxWrite(address, value);
}
void DmxSimpleClass::begin()
{
dmxBegin();
}
void DmxSimpleClass::end()
{
dmxEnd();
}
DmxSimpleClass DmxSimple;