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 7f2559254d4ab5e56c51bc7c9d36e9ca23996bad..2a0028f4a4f598250af2cd38f32b549abf38b031 100644 (file)
--- 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 fff2ae8df7d32a5fc90c10a99a86c8d517e9c667..9899cb90ef2556bf4e18f1fda89e8847a79c405c 100644 (file)
--- 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 (file)
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 (file)
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__ */