From: Jonathan McDowell <noodles@earth.li>
Date: Thu, 3 May 2018 21:26:36 +0000 (+0100)
Subject: Add initial 1-Wire support and use it for the USB serial #
X-Git-Url: https://the.earth.li/gitweb/?p=temper-clone.git;a=commitdiff_plain;h=0949ba3935c9c2ec778adc94eb25cdd65e3cba4e

Add initial 1-Wire support and use it for the USB serial #

Introduce some basic bit-banging 1-Wire functions and use them to
detect if there is a 1-Wire device present and if so use its ROM ID
as the USB serial number.
---

diff --git a/Makefile b/Makefile
index 7f25592..2a0028f 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@ CFLAGS = -Iusbdrv -Ilibs-device -I.
 AVRCC = avr-gcc -Wall -Os -DF_CPU=$(F_CPU) $(CFLAGS) -mmcu=$(DEVICE)
 
 OBJECTS = usbdrv/usbdrv.o usbdrv/usbdrvasm.o usbdrv/oddebug.o \
-	libs-device/osccalASM.o main.o
+	libs-device/osccalASM.o main.o w1.o
 
 all: main.hex
 
diff --git a/main.c b/main.c
index fff2ae8..9899cb9 100644
--- a/main.c
+++ b/main.c
@@ -30,6 +30,8 @@
 #include "usbdrv.h"
 #include "libs-device/osccal.h"
 
+#include "w1.h"
+
 typedef struct {
 	uint8_t modifier;
 	uint8_t reserved;
@@ -190,6 +192,30 @@ PROGMEM const char usbDescriptorConfiguration[] = {
 	USB_CFG_INTR_POLL_INTERVAL,	/* in ms */
 };
 
+inline char hexdigit(unsigned int i)
+{
+	return (i < 10) ? ('0' + i) : ('A' - 10 + i);
+}
+
+/* Look for a 1-Wire device and use its ROMID to set the serial ID */
+void set_serial(void)
+{
+	uint8_t buf[8];
+	uint8_t i;
+
+	if (!w1_reset()) {
+		return;
+	}
+
+	w1_write(0x33);		/* READ ROM */
+	w1_read(buf, 8);
+
+	for (i = 0; i < 8; i++) {
+		serno_str[i * 2 + 1] = hexdigit(buf[i] >> 4);
+		serno_str[i * 2 + 2] = hexdigit(buf[i] & 0xF);
+	}
+}
+
 usbMsgLen_t usbFunctionDescriptor(usbRequest_t *rq)
 {
 	if (rq->wValue.bytes[1] == USBDESCR_STRING &&
@@ -308,6 +334,9 @@ int main(void)
 
 	wdt_enable(WDTO_1S);
 
+	w1_setup();
+	set_serial();
+
 	usbInit();
 	usbDeviceDisconnect();
 
diff --git a/w1.c b/w1.c
new file mode 100644
index 0000000..8217602
--- /dev/null
+++ b/w1.c
@@ -0,0 +1,126 @@
+/*
+ * 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);
+}
diff --git a/w1.h b/w1.h
new file mode 100644
index 0000000..54c9f5b
--- /dev/null
+++ b/w1.h
@@ -0,0 +1,13 @@
+#ifndef __W1_H__
+#define __W1_H__
+
+#define W1_PIN 0	/* Pin 0 on Port B */
+
+uint8_t w1_crc(uint8_t *buf, uint8_t len);
+void w1_write(uint8_t val);
+uint8_t w1_read_byte();
+void w1_read(uint8_t *buf, uint8_t len);
+bool w1_reset(void);
+void w1_setup(void);
+
+#endif /* __W1_H__ */