git-svn-id: https://svn.salfter.gotdns.org/svn/a2bfc/trunk@83 1b90f75b-8b96-4784-87c0-14078182fce6

main.c

@@ -6,6 +6,7 @@
 int main (void)
 {
   unsigned char devid[8]={40,12,203,62,0,0,0,108};
+  short i;
 
   // activate temperature sensor
   if (ow_reset())
@@ -18,6 +19,8 @@ int main (void)
   {
     do
     {
+      for (i=0; i<500; i++)
+        ow_mswait();
       printf("%i deg F\n", ow_temp_read(devid, OW_TEMP_FAHRENHEIT));
     }
     while (!kbhit());

ow-apple2.s

@@ -5,6 +5,7 @@
 	.export _ow_read_impl
 	.export _ow_reset_impl
 	.export _ow_wait_impl
+	.export _ow_mswait_impl
 
 ; timing loops assume standard ~1 MHz speed for unaccelerated
 ; 8-bit Apple IIs
@@ -100,3 +101,13 @@ _ow_wait_impl:
 :	bit	PB2
 	bpl	:-
 	rts
+
+; wait 1 ms
+_ow_mswait_impl:
+	ldy	#100	;100*10=1000 us=1 ms
+:	nop
+	nop
+	nop
+	dey
+	bne	:-
+	rts

ow-common.s

@@ -6,6 +6,7 @@
 	.export	_ow_readbyte
 	.export _ow_reset
 	.export _ow_wait
+	.export _ow_mswait
 
 ; provided by system-specific routines at link time
 
@@ -14,6 +15,7 @@
 	.import	_ow_read_impl
 	.import	_ow_reset_impl
 	.import _ow_wait_impl
+	.import _ow_mswait_impl
 
 	.bss
 
@@ -26,6 +28,7 @@ owtmp:	.res	1
 _ow_send1	:=	_ow_send1_impl
 _ow_send0	:=	_ow_send0_impl
 _ow_wait	:=	_ow_wait_impl
+_ow_mswait	:=	_ow_mswait_impl
 
 ; reset bus: return 0 if 1-Wire devices present, 1 otherwise
 

ow-temp.c

@@ -2,21 +2,26 @@
 
 short ow_temp_read(unsigned char* devid, unsigned char format)
 {
-  unsigned char t1, t2;
+  unsigned char data[8];
   short rawtemp;
+  unsigned char i;
 
   if (devid[0]!=40)
     return OW_ERR_INVALIDDEVICE;
-  ow_selectdevice(devid);
+  do
-  ow_writebyte(68); // ask for a temperature reading
+  {
-  ow_wait(); // wait for operation to complete
+    ow_selectdevice(devid);
-  ow_selectdevice(devid);
+    ow_writebyte(68); // ask for a temperature reading
-  ow_writebyte(190); // retrieve the reading  
+    ow_wait(); // wait for operation to complete
-  t1=ow_readbyte();
+    ow_selectdevice(devid);
-  t2=ow_readbyte();
+    ow_writebyte(190); // retrieve the reading
-  ow_reset();
+    for (i=0; i<8; i++)
+      data[i]=ow_readbyte();
+    ow_mswait();
+  }
+  while (ow_crc(data,8)!=0); // repeat until we get a valid reading
   
-  rawtemp=(short)(t1+((int)t2<<8));
+  rawtemp=(short)(data[0]+((int)data[1]<<8));
   switch (format)
   {
   case OW_TEMP_FAHRENHEIT:
@@ -28,3 +33,4 @@ short ow_temp_read(unsigned char* devid, unsigned char format)
     return rawtemp;
   }
 }
+

ow-temp.h

@@ -4,6 +4,7 @@
 #include "ow.h"
 
 // 1-Wire temperature sensor functions
+// (works with DS18B20; unknown if it'll work with others)
 
 short ow_temp_read(unsigned char* devid, unsigned char format);
 

ow.c

@@ -1,5 +1,25 @@
 #include "ow.h"
 
+unsigned char ow_crc_lookup[256]=
+{
+  0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65,
+  157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220,
+  35, 125, 159, 193, 66, 28, 254, 160, 225, 191, 93, 3, 128, 222, 60, 98,
+  190, 224, 2, 92, 223, 129, 99, 61, 124, 34, 192, 158, 29, 67, 161, 255,
+  70, 24, 250, 164, 39, 121, 155, 197, 132, 218, 56, 102, 229, 187, 89, 7,
+  219, 133, 103, 57, 186, 228, 6, 88, 25, 71, 165, 251, 120, 38, 196, 154,
+  101, 59, 217, 135, 4, 90, 184, 230, 167, 249, 27, 69, 198, 152, 122, 36,
+  248, 166, 68, 26, 153, 199, 37, 123, 58, 100, 134, 216, 91, 5, 231, 185,
+  140, 210, 48, 110, 237, 179, 81, 15, 78, 16, 242, 172, 47, 113, 147, 205,
+  17, 79, 173, 243, 112, 46, 204, 146, 211, 141, 111, 49, 178, 236, 14, 80,
+  175, 241, 19, 77, 206, 144, 114, 44, 109, 51, 209, 143, 12, 82, 176, 238,
+  50, 108, 142, 208, 83, 13, 239, 177, 240, 174, 76, 18, 145, 207, 45, 115,
+  202, 148, 118, 40, 171, 245, 23, 73, 8, 86, 180, 234, 105, 55, 213, 139,
+  87, 9, 235, 181, 54, 104, 138, 212, 149, 203, 41, 119, 244, 170, 72, 22,
+  233, 183, 85, 11, 136, 214, 52, 106, 43, 117, 151, 201, 74, 20, 246, 168,
+  116, 42, 200, 150, 21, 75, 169, 247, 182, 232, 10, 84, 215, 137, 107, 53
+};
+
 void ow_selectdevice(unsigned char* devid)
 {
   ow_reset();
@@ -14,3 +34,14 @@ void ow_selectdevice(unsigned char* devid)
   ow_writebyte(devid[7]);
   return;
 }
+
+unsigned char ow_crc(unsigned char* data, unsigned char len)
+{
+  unsigned char crc=0;
+  unsigned char i;
+  
+  for (i=0; i<len; i++)
+    crc^=ow_crc_lookup[data[i]];
+  return crc;
+}
+

ow.h

@@ -9,10 +9,12 @@ unsigned char __fastcall__ ow_readbit(void);
 unsigned char __fastcall__ ow_readbyte(void);
 unsigned char __fastcall__ ow_reset(void);
 void __fastcall__ ow_wait(void);
+void __fastcall__ ow_mswait(void);
 
 // common C routines in ow.c
 
 void ow_selectdevice(unsigned char* devid);
+unsigned char ow_crc(unsigned char* data, unsigned char len);
 
 // common 1-Wire constants