porklib: Simple library for programming Arduino in C
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avr-lib/examples/dht11/lib/onewire.c

226 lines
4.1 KiB

9 years ago
#include <avr/io.h>
#include <util/delay.h>
#include <stdint.h>
#include <stdbool.h>
#include "iopins.h"
#include "onewire.h"
/** Perform bus reset. Returns true if any device is connected */
bool ow_reset(const uint8_t pin)
{
as_output_n(pin);
pin_low_n(pin);
_delay_us(480);
as_input_pu_n(pin);
_delay_us(70);
const bool a = get_pin_n(pin);
_delay_us(410);
return a;
}
/** Send a single bit */
void _ow_tx_bit(const uint8_t pin, const bool bit)
{
as_output_n(pin);
pin_low_n(pin);
if (bit) {
_delay_us(6);
as_input_pu_n(pin);
_delay_us(64);
} else {
_delay_us(60);
as_input_pu_n(pin);
_delay_us(10);
}
}
/** Send a single byte */
void ow_send(const uint8_t pin, const uint8_t byte)
{
for (uint8_t i = 0; i < 8; i++)
{
_ow_tx_bit(pin, (byte >> i) & 0x01);
}
}
/** Read a single bit */
bool _ow_rx_bit(const uint8_t pin)
{
as_output_n(pin);
pin_low_n(pin);
_delay_us(6);
as_input_pu_n(pin);
_delay_us(9);
const bool a = get_pin_n(pin);
_delay_us(55);
return a;
}
/** Read a single byte */
uint8_t ow_read(const uint8_t pin)
{
uint8_t byte = 0;
for (uint8_t i = 0; i < 8; i++)
{
byte = (byte >> 1) | (_ow_rx_bit(pin) << 7);
}
return byte;
}
/** Wait until the device is ready. Returns false on timeout */
bool ow_wait_ready(const uint8_t pin)
{
uint16_t timeout = 700;
as_input_pu_n(pin);
while (--timeout > 0)
{
if (is_high_n(pin)) return true;
_delay_ms(1);
}
return false;
}
/** Read bytes into an array */
void ow_read_arr(const uint8_t pin, uint8_t* array, const uint8_t count)
{
for (uint8_t i = 0; i < count; i++)
{
array[i] = ow_read(pin);
}
}
// ---------- CRC utils ----------
/*
Dallas 1-wire CRC routines for Arduino with examples of usage.
The 16-bit routine is new.
The 8-bit routine is from http://github.com/paeaetech/paeae/tree/master/Libraries/ds2482/
Copyright (C) 2010 Kairama Inc
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 3 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.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// Dallas 1-wire 16-bit CRC calculation. Developed from Maxim Application Note 27.
/** Compute a CRC16 checksum */
uint16_t crc16( uint8_t *data, uint8_t len)
{
uint16_t crc = 0;
for (uint8_t i = 0; i < len; i++)
{
uint8_t inbyte = data[i];
for (uint8_t j = 0; j < 8; j++)
{
uint8_t mix = (crc ^ inbyte) & 0x01;
crc = crc >> 1;
if (mix)
crc = crc ^ 0xA001;
inbyte = inbyte >> 1;
}
}
return crc;
}
// The 1-Wire CRC scheme is described in Maxim Application Note 27:
// "Understanding and Using Cyclic Redundancy Checks with Maxim iButton Products"
/** Compute a CRC8 checksum */
uint8_t crc8(uint8_t *addr, uint8_t len)
{
uint8_t crc = 0;
for (uint8_t i = 0; i < len; i++)
{
uint8_t inbyte = addr[i];
for (uint8_t j = 0; j < 8; j++)
{
uint8_t mix = (crc ^ inbyte) & 0x01;
crc >>= 1;
if (mix)
crc ^= 0x8C;
inbyte >>= 1;
}
}
return crc;
}
// --- utils for DS1820 ---
/** Read temperature in 0.0625°C, or TEMP_ERROR on error */
int16_t ds1820_read_temp(uint8_t pin)
{
ow_send(pin, READ_SCRATCHPAD);
uint8_t bytes[9];
ow_read_arr(pin, bytes, 9);
uint8_t crc = crc8(bytes, 8);
if (crc != bytes[8]) {
return TEMP_ERROR;
} else {
int16_t a = ((bytes[1] << 8) | bytes[0]) >> 1;
a = a << 4;
a += (16 - bytes[6]) & 0x0F;
a -= 0x04;
return a;
}
}
/** Read temperature in 0.1°C, or TEMP_ERROR on error */
int16_t ds1820_read_temp_c(uint8_t pin)
{
int32_t temp = ds1820_read_temp(pin);
if (temp == TEMP_ERROR)
return TEMP_ERROR;
temp *= 625;
uint16_t rem = temp % 1000;
temp /= 1000;
if (rem >= 500) temp++;
return (int16_t) temp;
}