From: Michael McMaster <michael@codesrc.com>
Date: Wed, 14 Nov 2012 11:11:32 +0000 (+1000)
Subject: Tested to work.
X-Git-Tag: 1.0^0
X-Git-Url: http://git.codesrc.com/gitweb.cgi?a=commitdiff_plain;h=HEAD;p=chickenFan.git

Tested to work.
Finished.
---

diff --git a/BOM.ods b/BOM.ods
new file mode 100644
index 0000000..e3d5fbd
Binary files /dev/null and b/BOM.ods differ
diff --git a/Makefile b/Makefile
index 36c577b..999e6c6 100644
--- a/Makefile
+++ b/Makefile
@@ -23,8 +23,8 @@ chickenFan.elf: chickenFan.c
 	avr-gcc -Wall -Os -std=c99 -mmcu=attiny25 $^ -o $@
 
 # Use with arduinoisp example sketch. See http://hlt.media.mit.edu/?p=1706
-.PHONY: program
-program: chickenFan.hex
+.PHONY: burn
+burn: chickenFan.hex
 	avrdude -P /dev/ttyUSB0 -b 19200 -c avrisp -p t25 -v -e -U flash:w:chickenFan.hex
 
 .PHONY: clean
diff --git a/chickenFan.c b/chickenFan.c
index 2cb98ac..9a20904 100644
--- a/chickenFan.c
+++ b/chickenFan.c
@@ -32,6 +32,7 @@
 //		required for avr-libc delay functions.
 //
 // avr-libc: tested with 1.8.0
+//
 
 // 1 MHz internal oscillator. Assumes default fuse settings.
 #define F_CPU 1000000UL
@@ -46,13 +47,13 @@
 
 #define SETBIT(port, bitnum) port |= _BV(bitnum)
 #define CLRBIT(port, bitnum) port &= (uint8_t) ~_BV(bitnum)
-#define READBIT(port, bitnum) (!!(port & _BV(bitnum)))
+#define READBIT(port, bitnum) (port & (_BV(bitnum)))
 
 
 // One-Wire active-low protocol
 #define ONEWIRE_PIN PB0
-#define ONEWIRE_LOW() {SETBIT(DDRB, ONEWIRE_PIN); CLRBIT(PORTB, ONEWIRE_PIN); }
-#define ONEWIRE_HI() CLRBIT(DDRB, ONEWIRE_PIN)
+#define ONEWIRE_LOW() SETBIT(DDRB, ONEWIRE_PIN);
+#define ONEWIRE_HI() CLRBIT(DDRB, ONEWIRE_PIN);
 #define ONEWIRE_READ() READBIT(PINB, ONEWIRE_PIN)
 
 static void oneWireInit()
@@ -69,6 +70,9 @@ static void oneWireInit()
 		// Ok, we're -supposed- to check that the slave device
 		// also pulls the line low, but we just assume it will
 		// and wait until it has finished.
+
+		// Tests with a CRO show the DS18B20 holding the line low
+		// for 100us. (datasheet says 60-240us)
 	}
 	_delay_us(480);
 }
@@ -78,21 +82,21 @@ static void oneWireWrite(uint8_t value)
 	// LSB first, active low
 	for (int i = 0; i < 8; ++i)
 	{
-		ONEWIRE_LOW();
-
 		if (value & _BV(i))
 		{
-			// Min 1uS delay taken care of by ifcondition.
-			// Don't tempt fate by waiting too long.
-
+			ONEWIRE_LOW();
 			ONEWIRE_HI();
 			_delay_us(60);
 		}
 		else
 		{
+			ONEWIRE_LOW();
 			_delay_us(60);
 			ONEWIRE_HI();
+			// Ensure the weak pullup has time to work
+			_delay_us(4);
 		}
+
 		_NOP(); // 1uS recovery time. Probably not needed.
 	}
 }
@@ -106,14 +110,21 @@ static uint8_t oneWireReadBit()
 	// we need to read it towards the END of that 15uS
 	// period.
 
-	ONEWIRE_LOW(); // Up to 4 cycles ?
-	_NOP(); // Ensure we wait 1us
+	ONEWIRE_LOW(); //2 cycles
 	ONEWIRE_HI(); // 2 cycles
+
+	// We -start- going high 5 cycles after going low.
+	// 2.5V ~ 2ms later. 5V ~ 4ms later.
+	// Need to leave sufficient time for the weak 10k pullup
+	// to raise the bus or else we'll read 0 instead of 1,
+	// but still sample early enough before the time slot
+	// runs out.
+	_NOP();
+	_NOP();
 	_NOP();
 	_NOP();
 	_NOP();
 	_NOP();
-	_NOP(); // Up to 12 cycles since the pin went low.
 	uint8_t bit = ONEWIRE_READ(); // 2 cycles for I/O access?
 
 	_delay_us(60); // Ensure we wait out the rest of the read slot.
@@ -121,13 +132,18 @@ static uint8_t oneWireReadBit()
 	return bit;
 }
 
-static uint8_t oneWireRead()
+uint8_t oneWireRead()
 {
 	uint8_t result = 0;
+	uint8_t mask = 1;
 	// LSB first, active low
-	for (int i = 0; i < 8; ++ i)
+	for (uint8_t i = 0; i < 8; ++i)
 	{
-		result |= oneWireReadBit() << i;
+		if (oneWireReadBit())
+		{
+			result |= mask;
+		}
+		mask <<= 1;
 	}
 	return result;
 }
diff --git a/chickenFan.hex b/chickenFan.hex
index 02c9f9d..b36c262 100644
--- a/chickenFan.hex
+++ b/chickenFan.hex
@@ -1,20 +1,19 @@
 :100000000EC013C012C011C010C00FC00EC00DC072
 :100010000CC00BC00AC009C008C007C006C011242C
-:100020001FBECFEDCDBF3CD07DC0EACFB89AC098FF
-:1000300080EA8A95F1F7B8980000B099FECF80EA7F
-:100040008A95F1F7089520E030E090E0B89AC098E2
-:10005000AC01022E02C0559547950A94E2F740FF85
-:1000600005C0B89844E14A95F1F704C044E14A95C7
-:10007000F1F7B89800002F5F3F4F2830310531F776
-:100080000895B89AC0980000B898000000000000D9
-:100090000000000086B394E19A95F1F7817008950D
-:1000A000BC9AC498C3DF8CECCEDF84E4CCDFE9DFFC
-:1000B0008823E9F3BBDF8CECC6DF8EEBC4DFC0E046
-:1000C000D0E010E0DEDF0C2E01C0880F0A94EAF7C2
-:1000D000182B2196C830D105A9F7C0E0D0E000E088
-:1000E000D0DF0C2E01C0880F0A94EAF7082B219666
-:1000F000C830D105A9F7802F8295807F12951F7097
-:10010000812B893114F0C49A03C0883109F0C49856
-:100110008FE79AE126E0815090402040E1F700C04F
-:080120000000C0CFF894FFCFEE
+:100020001FBECFEDCDBF4CD073C0EACFB89A80EAE7
+:100030008A95F1F7B8980000B099FECF80EA8A95CA
+:10004000F1F7089520E030E090E0AC01022E02C00C
+:10005000559547950A94E2F7B89A40FF05C0B898BD
+:1000600044E14A95F1F706C044E14A95F1F7B898A2
+:1000700000C000C000002F5F3F4F2830310529F736
+:100080000895B89AB8980000000000000000000031
+:10009000000086B394E19A95F1F7817008951F935B
+:1000A000CF93DF93D8E011E0C0E0EBDF8111C12BEB
+:1000B000110FD150D1F78C2FDF91CF911F9108955F
+:1000C000BC9AC498B3DF8CECBDDF84E4BBDFD9DF1E
+:1000D0008823E9F3ABDF8CECB5DF8EEBB3DFDFDF3A
+:1000E000C82FDDDF8295807FC295CF708C2B893140
+:1000F00014F0C49A03C0883109F0C4982FE78AE14C
+:1001000096E0215080409040E1F700C00000DACF37
+:04011000F894FFCF91
 :00000001FF