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Arduino/targets/arduino/wiring.c
2006-11-23 16:02:55 +00:00

591 lines
14 KiB
C
Executable File

/*
wiring.c - Partial implementation of the Wiring API for the ATmega8.
Part of Arduino - http://www.arduino.cc/
Copyright (c) 2005-2006 David A. Mellis
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General
Public License along with this library; if not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330,
Boston, MA 02111-1307 USA
$Id$
*/
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/signal.h>
#include <avr/delay.h>
#include <stdio.h>
#include <stdarg.h>
#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif
#include "wiring.h"
// Define constants and variables for buffering incoming serial data. We're
// using a ring buffer (I think), in which rx_buffer_head is the index of the
// location to which to write the next incoming character and rx_buffer_tail
// is the index of the location from which to read
#define RX_BUFFER_SIZE 128
unsigned char rx_buffer[RX_BUFFER_SIZE];
int rx_buffer_head = 0;
int rx_buffer_tail = 0;
// The number of times timer 0 has overflowed since the program started.
// Must be volatile or gcc will optimize away some uses of it.
volatile unsigned long timer0_overflow_count;
// Get the hardware port of the given virtual pin number. This comes from
// the pins_*.c file for the active board configuration.
int digitalPinToPort(int pin)
{
return digital_pin_to_port[pin].port;
}
// Get the bit location within the hardware port of the given virtual pin.
// This comes from the pins_*.c file for the active board configuration.
int digitalPinToBit(int pin)
{
return digital_pin_to_port[pin].bit;
}
int analogOutPinToTimer(int pin)
{
return analog_out_pin_to_timer[pin];
}
int analogInPinToBit(int pin)
{
return analog_in_pin_to_port[pin].bit;
}
void pinMode(int pin, int mode)
{
if (digitalPinToPort(pin) != NOT_A_PIN) {
if (mode == INPUT)
cbi(_SFR_IO8(port_to_mode[digitalPinToPort(pin)]),
digitalPinToBit(pin));
else
sbi(_SFR_IO8(port_to_mode[digitalPinToPort(pin)]),
digitalPinToBit(pin));
}
}
void digitalWrite(int pin, int val)
{
if (digitalPinToPort(pin) != NOT_A_PIN) {
// If the pin that support PWM output, we need to turn it off
// before doing a digital write.
if (analogOutPinToTimer(pin) == TIMER1A)
cbi(TCCR1A, COM1A1);
if (analogOutPinToTimer(pin) == TIMER1B)
cbi(TCCR1A, COM1B1);
#if defined(__AVR_ATmega168__)
if (analogOutPinToTimer(pin) == TIMER0A)
cbi(TCCR0A, COM0A1);
if (analogOutPinToTimer(pin) == TIMER0B)
cbi(TCCR0A, COM0B1);
if (analogOutPinToTimer(pin) == TIMER2A)
cbi(TCCR2A, COM2A1);
if (analogOutPinToTimer(pin) == TIMER2B)
cbi(TCCR2A, COM2B1);
#else
if (analogOutPinToTimer(pin) == TIMER2)
cbi(TCCR2, COM21);
#endif
if (val == LOW)
cbi(_SFR_IO8(port_to_output[digitalPinToPort(pin)]),
digitalPinToBit(pin));
else
sbi(_SFR_IO8(port_to_output[digitalPinToPort(pin)]),
digitalPinToBit(pin));
}
}
int digitalRead(int pin)
{
if (digitalPinToPort(pin) != NOT_A_PIN) {
// If the pin that support PWM output, we need to turn it off
// before getting a digital reading.
if (analogOutPinToTimer(pin) == TIMER1A)
cbi(TCCR1A, COM1A1);
if (analogOutPinToTimer(pin) == TIMER1B)
cbi(TCCR1A, COM1B1);
#if defined(__AVR_ATmega168__)
if (analogOutPinToTimer(pin) == TIMER0A)
cbi(TCCR0A, COM0A1);
if (analogOutPinToTimer(pin) == TIMER0B)
cbi(TCCR0A, COM0B1);
if (analogOutPinToTimer(pin) == TIMER2A)
cbi(TCCR2A, COM2A1);
if (analogOutPinToTimer(pin) == TIMER2B)
cbi(TCCR2A, COM2B1);
#else
if (analogOutPinToTimer(pin) == TIMER2)
cbi(TCCR2, COM21);
#endif
return (_SFR_IO8(port_to_input[digitalPinToPort(pin)]) >>
digitalPinToBit(pin)) & 0x01;
}
return LOW;
}
int analogRead(int pin)
{
unsigned int low, high, ch = analogInPinToBit(pin);
// the low 4 bits of ADMUX select the ADC channel
ADMUX = (ADMUX & (unsigned int) 0xf0) | (ch & (unsigned int) 0x0f);
// without a delay, we seem to read from the wrong channel
delay(1);
// start the conversion
sbi(ADCSRA, ADSC);
// ADSC is cleared when the conversion finishes
while (bit_is_set(ADCSRA, ADSC));
// we have to read ADCL first; doing so locks both ADCL
// and ADCH until ADCH is read. reading ADCL second would
// cause the results of each conversion to be discarded,
// as ADCL and ADCH would be locked when it completed.
low = ADCL;
high = ADCH;
// combine the two bytes
return (high << 8) | low;
}
// Right now, PWM output only works on the pins with
// hardware support. These are defined in the appropriate
// pins_*.c file. For the rest of the pins, we default
// to digital output.
void analogWrite(int pin, int val)
{
// We need to make sure the PWM output is enabled for those pins
// that support it, as we turn it off when digitally reading or
// writing with them. Also, make sure the pin is in output mode
// for consistenty with Wiring, which doesn't require a pinMode
// call for the analog output pins.
pinMode(pin, OUTPUT);
if (analogOutPinToTimer(pin) == TIMER1A) {
// connect pwm to pin on timer 1, channel A
sbi(TCCR1A, COM1A1);
// set pwm duty
OCR1A = val;
} else if (analogOutPinToTimer(pin) == TIMER1B) {
// connect pwm to pin on timer 1, channel B
sbi(TCCR1A, COM1B1);
// set pwm duty
OCR1B = val;
#if defined(__AVR_ATmega168__)
} else if (analogOutPinToTimer(pin) == TIMER0A) {
// connect pwm to pin on timer 0, channel A
sbi(TCCR0A, COM0A1);
// set pwm duty
OCR0A = val;
} else if (analogOutPinToTimer(pin) == TIMER0B) {
// connect pwm to pin on timer 0, channel B
sbi(TCCR0A, COM0B1);
// set pwm duty
OCR0B = val;
} else if (analogOutPinToTimer(pin) == TIMER2A) {
// connect pwm to pin on timer 2, channel A
sbi(TCCR2A, COM2A1);
// set pwm duty
OCR2A = val;
} else if (analogOutPinToTimer(pin) == TIMER2B) {
// connect pwm to pin on timer 2, channel B
sbi(TCCR2A, COM2B1);
// set pwm duty
OCR2B = val;
#else
} else if (analogOutPinToTimer(pin) == TIMER2) {
// connect pwm to pin on timer 2, channel B
sbi(TCCR2, COM21);
// set pwm duty
OCR2 = val;
#endif
} else if (val < 128)
digitalWrite(pin, LOW);
else
digitalWrite(pin, HIGH);
}
void beginSerial(long baud)
{
UBRRH = ((F_CPU / 16 + baud / 2) / baud - 1) >> 8;
UBRRL = ((F_CPU / 16 + baud / 2) / baud - 1);
// enable rx and tx
sbi(UCSRB, RXEN);
sbi(UCSRB, TXEN);
// enable interrupt on complete reception of a byte
sbi(UCSRB, RXCIE);
// defaults to 8-bit, no parity, 1 stop bit
}
void serialWrite(unsigned char c)
{
#if defined(__AVR_ATmega168__)
while (!(UCSR0A & (1 << UDRE0)))
;
UDR0 = c;
#else
while (!(UCSRA & (1 << UDRE)))
;
UDR = c;
#endif
}
int serialAvailable()
{
return (rx_buffer_head - rx_buffer_tail) % RX_BUFFER_SIZE;
}
int serialRead()
{
// if the head isn't ahead of the tail, we don't have any characters
if (rx_buffer_head == rx_buffer_tail) {
return -1;
} else {
unsigned char c = rx_buffer[rx_buffer_tail];
rx_buffer_tail = (rx_buffer_tail + 1) % RX_BUFFER_SIZE;
return c;
}
}
SIGNAL(SIG_UART_RECV)
{
unsigned char c = UDR;
int i = (rx_buffer_head + 1) % RX_BUFFER_SIZE;
// if we should be storing the received character into the location
// just before the tail (meaning that the head would advance to the
// current location of the tail), we're about to overflow the buffer
// and so we don't write the character or advance the head.
if (i != rx_buffer_tail) {
rx_buffer[rx_buffer_head] = c;
rx_buffer_head = i;
}
}
void printMode(int mode)
{
// do nothing, we only support serial printing, not lcd.
}
void printByte(unsigned char c)
{
serialWrite(c);
}
void printNewline()
{
printByte('\n');
}
void printString(char *s)
{
while (*s)
printByte(*s++);
}
void printIntegerInBase(unsigned long n, unsigned long base)
{
unsigned char buf[8 * sizeof(long)]; // Assumes 8-bit chars.
unsigned long i = 0;
if (n == 0) {
printByte('0');
return;
}
while (n > 0) {
buf[i++] = n % base;
n /= base;
}
for (; i > 0; i--)
printByte(buf[i - 1] < 10 ?
'0' + buf[i - 1] :
'A' + buf[i - 1] - 10);
}
void printInteger(long n)
{
if (n < 0) {
printByte('-');
n = -n;
}
printIntegerInBase(n, 10);
}
void printHex(unsigned long n)
{
printIntegerInBase(n, 16);
}
void printOctal(unsigned long n)
{
printIntegerInBase(n, 8);
}
void printBinary(unsigned long n)
{
printIntegerInBase(n, 2);
}
/* Including print() adds approximately 1500 bytes to the binary size,
* so we replace it with the smaller and less-confusing printString(),
* printInteger(), etc.
void print(const char *format, ...)
{
char buf[256];
va_list ap;
va_start(ap, format);
vsnprintf(buf, 256, format, ap);
va_end(ap);
printString(buf);
}
*/
SIGNAL(SIG_OVERFLOW0)
{
timer0_overflow_count++;
}
unsigned long millis()
{
// timer 0 increments every 64 cycles, and overflows when it reaches 256.
// we would calculate the total number of clock cycles, then divide by the
// number of clock cycles per millisecond, but this overflows too often.
//return timer0_overflow_count * 64UL * 256UL / (F_CPU / 1000UL);
// instead find 1/128th the number of clock cycles and divide by 1/128th
// the number of clock cycles per millisecond
return timer0_overflow_count * 64UL * 2UL / (F_CPU / 128000UL);
}
void delay(unsigned long ms)
{
unsigned long start = millis();
while (millis() - start < ms)
;
}
/* Delay for the given number of microseconds. Assumes a 16 MHz clock.
* Disables interrupts, which will disrupt the millis() function if used
* too frequently. */
void delayMicroseconds(unsigned int us)
{
// calling avrlib's delay_us() function with low values (e.g. 1 or
// 2 microseconds) gives delays longer than desired.
//delay_us(us);
// for a one-microsecond delay, simply return. the overhead
// of the function call yields a delay of approximately 1 1/8 us.
if (--us == 0)
return;
// the following loop takes a quarter of a microsecond (4 cycles)
// per iteration, so execute it four times for each microsecond of
// delay requested.
us <<= 2;
// account for the time taken in the preceeding commands.
us -= 2;
// disable interrupts, otherwise the timer 0 overflow interrupt that
// tracks milliseconds will make us delay longer than we want.
cli();
// busy wait
__asm__ __volatile__ (
"1: sbiw %0,1" "\n\t" // 2 cycles
"brne 1b" : "=w" (us) : "0" (us) // 2 cycles
);
// reenable interrupts.
sei();
}
/*
unsigned long pulseIn(int pin, int state)
{
unsigned long width = 0;
while (digitalRead(pin) == !state)
;
while (digitalRead(pin) != !state)
width++;
return width * 17 / 2; // convert to microseconds
}
*/
/* Measures the length (in microseconds) of a pulse on the pin; state is HIGH
* or LOW, the type of pulse to measure. Works on pulses from 10 microseconds
* to 3 minutes in length, but must be called at least N microseconds before
* the start of the pulse. */
unsigned long pulseIn(int pin, int state)
{
// cache the port and bit of the pin in order to speed up the
// pulse width measuring loop and achieve finer resolution. calling
// digitalRead() instead yields much coarser resolution.
int r = port_to_input[digitalPinToPort(pin)];
int bit = digitalPinToBit(pin);
int mask = 1 << bit;
unsigned long width = 0;
// compute the desired bit pattern for the port reading (e.g. set or
// clear the bit corresponding to the pin being read). the !!state
// ensures that the function treats any non-zero value of state as HIGH.
state = (!!state) << bit;
// wait for the pulse to start
while ((_SFR_IO8(r) & mask) != state)
;
// wait for the pulse to stop
while ((_SFR_IO8(r) & mask) == state)
width++;
// convert the reading to microseconds. the slower the CPU speed, the
// proportionally fewer iterations of the loop will occur (e.g. a
// 4 MHz clock will yield a width that is one-fourth of that read with
// a 16 MHz clock). each loop was empirically determined to take
// approximately 23/20 of a microsecond with a 16 MHz clock.
return width * (16000000UL / F_CPU) * 20 / 23;
}
int main(void)
{
// this needs to be called before setup() or some functions won't
// work there
sei();
// timer 0 is used for millis() and delay()
timer0_overflow_count = 0;
// on the ATmega168, timer 0 is also used for fast hardware pwm
// (using phase-correct PWM would mean that timer 0 overflowed half as often
// resulting in different millis() behavior on the ATmega8 and ATmega168)
#if defined(__AVR_ATmega168__)
sbi(TCCR0A, WGM01);
sbi(TCCR0A, WGM00);
#endif
// set timer 0 prescale factor to 64
#if defined(__AVR_ATmega168__)
sbi(TCCR0B, CS01);
sbi(TCCR0B, CS00);
#else
sbi(TCCR0, CS01);
sbi(TCCR0, CS00);
#endif
// enable timer 0 overflow interrupt
#if defined(__AVR_ATmega168__)
sbi(TIMSK0, TOIE0);
#else
sbi(TIMSK, TOIE0);
#endif
// timers 1 and 2 are used for phase-correct hardware pwm
// this is better for motors as it ensures an even waveform
// note, however, that fast pwm mode can achieve a frequency of up
// 8 MHz (with a 16 MHz clock) at 50% duty cycle
// set timer 1 prescale factor to 64
sbi(TCCR1B, CS11);
sbi(TCCR1B, CS10);
// put timer 1 in 8-bit phase correct pwm mode
sbi(TCCR1A, WGM10);
// set timer 2 prescale factor to 64
#if defined(__AVR_ATmega168__)
sbi(TCCR2B, CS22);
#else
sbi(TCCR2, CS22);
#endif
// configure timer 2 for phase correct pwm (8-bit)
#if defined(__AVR_ATmega168__)
sbi(TCCR2A, WGM20);
#else
sbi(TCCR2, WGM20);
#endif
// set a2d reference to AVCC (5 volts)
cbi(ADMUX, REFS1);
sbi(ADMUX, REFS0);
// set a2d prescale factor to 128
// 16 MHz / 128 = 125 KHz, inside the desired 50-200 KHz range.
// XXX: this will not work properly for other clock speeds, and
// this code should use F_CPU to determine the prescale factor.
sbi(ADCSRA, ADPS2);
sbi(ADCSRA, ADPS1);
sbi(ADCSRA, ADPS0);
// enable a2d conversions
sbi(ADCSRA, ADEN);
// the bootloader connects pins 0 and 1 to the USART; disconnect them here
// so they can be used as normal digital i/o; they will be reconnected in
// Serial.begin()
#if defined(__AVR_ATmega168__)
UCSR0B = 0;
#else
UCSRB = 0;
#endif
setup();
for (;;)
loop();
return 0;
}