X-Git-Url: https://the.earth.li/gitweb/?p=temper-clone.git;a=blobdiff_plain;f=w1.c;fp=w1.c;h=8217602e0dcaa277ace9d3614ba47c54d420e56a;hp=0000000000000000000000000000000000000000;hb=0949ba3935c9c2ec778adc94eb25cdd65e3cba4e;hpb=3c727aad6ec52918a14a6550349a2e2ca35d0645

diff --git a/w1.c b/w1.c
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+/*
+ * Basic routines to bit-bang standard 1-Wire via a GPIO pin
+ *
+ * Copyright 2018 Jonathan McDowell <noodles@earth.li>
+ *
+ * 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/>.
+ */
+#include <stdbool.h>
+#include <avr/io.h>
+#include <util/atomic.h>
+#include <util/delay.h>
+
+#include "w1.h"
+
+uint8_t w1_crc(uint8_t *buf, uint8_t len)
+{
+	uint8_t i, j, crc;
+
+	crc = 0;
+	for (i = 0; i < len; i++)
+	{
+		crc ^= buf[i];
+		for (j = 0; j < 8; j++)
+		{
+			crc = crc >> 1 ^ ((crc & 1) ? 0x8c : 0);
+		}
+	}
+
+	return crc;
+}
+
+void w1_write(uint8_t val)
+{
+	uint8_t i;
+
+	for (i = 0; i < 8; i++) {
+		ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+		{
+			/* Pull low for 6µs for 1, 60µs for 0 */
+			DDRB |= 1 << W1_PIN;
+			if (val & 1)
+				_delay_us(6);
+			else
+				_delay_us(60);
+			/* Release to make up to 70µs total */
+			DDRB &= ~(1 << W1_PIN);
+			if (val & 1)
+				_delay_us(64);
+			else
+				_delay_us(10);
+		}
+
+		val >>= 1;
+	}
+}
+
+uint8_t w1_read_byte()
+{
+	uint8_t i, val;
+
+	val = 0;
+	for (i = 0; i < 8; i++) {
+		ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+		{
+			/* Pull low for 6µs */
+			DDRB |= 1 << W1_PIN;
+			_delay_us(6);
+			/* Release for 9µs */
+			DDRB &= ~(1 << W1_PIN);
+			_delay_us(9);
+
+			/* Read the line state */
+			val |= ((PINB >> W1_PIN) & 1) << i;
+		}
+
+		_delay_us(55);
+	}
+
+	return val;
+}
+
+void w1_read(uint8_t *buf, uint8_t len)
+{
+	uint8_t i;
+
+	for (i = 0; i < len; i++) {
+		buf[i] = w1_read_byte();
+	}
+}
+
+bool w1_reset(void)
+{
+	bool present;
+
+	/* Pull low for 480µs */
+	DDRB |= 1 << W1_PIN;
+	_delay_us(480);
+	/* Release for 70µs */
+	DDRB &= ~(1 << W1_PIN);
+	_delay_us(70);
+
+	/* If there's a device present it'll have pulled the line low */
+	present = !((PINB >> W1_PIN) & 1);
+
+	/* Wait for reset to complete */
+	_delay_us(410);
+
+	return present;
+}
+
+void w1_setup(void)
+{
+	/* Set 1w pin to low */
+	PORTB &= (1 << W1_PIN);
+}