Module Name: src
Committed By: kardel
Date: Wed May 14 08:14:56 UTC 2014
Modified Files:
src/sys/dev/onewire: owtemp.c
Log Message:
calculate extended precision as per DS1920/DS1820 data sheets
To generate a diff of this commit:
cvs rdiff -u -r1.16 -r1.17 src/sys/dev/onewire/owtemp.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/dev/onewire/owtemp.c
diff -u src/sys/dev/onewire/owtemp.c:1.16 src/sys/dev/onewire/owtemp.c:1.17
--- src/sys/dev/onewire/owtemp.c:1.16 Mon Jun 20 17:24:16 2011
+++ src/sys/dev/onewire/owtemp.c Wed May 14 08:14:56 2014
@@ -1,4 +1,4 @@
-/* $NetBSD: owtemp.c,v 1.16 2011/06/20 17:24:16 pgoyette Exp $ */
+/* $NetBSD: owtemp.c,v 1.17 2014/05/14 08:14:56 kardel Exp $ */
/* $OpenBSD: owtemp.c,v 1.1 2006/03/04 16:27:03 grange Exp $ */
/*
@@ -22,7 +22,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: owtemp.c,v 1.16 2011/06/20 17:24:16 pgoyette Exp $");
+__KERNEL_RCSID(0, "$NetBSD: owtemp.c,v 1.17 2014/05/14 08:14:56 kardel Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@@ -64,7 +64,7 @@ CFATTACH_DECL_NEW(owtemp, sizeof(struct
extern struct cfdriver owtemp_cd;
static const struct onewire_matchfam owtemp_fams[] = {
- { ONEWIRE_FAMILY_DS1920 },
+ { ONEWIRE_FAMILY_DS1920 }, /* also DS1820 */
{ ONEWIRE_FAMILY_DS18B20 },
{ ONEWIRE_FAMILY_DS1822 },
};
@@ -235,6 +235,21 @@ owtemp_decode_ds1920(const uint8_t *buf)
temp = (int8_t)buf[1];
temp = (temp << 8) | buf[0];
- /* Convert to uK */
- return (temp * 500000 + 273150000);
+ if (buf[7] != 0) {
+ /*
+ * interpolate for higher precision using the count registers
+ *
+ * buf[7]: COUNT_PER_C(elsius)
+ * buf[6]: COUNT_REMAIN
+ *
+ * T = TEMP - 0.25 + (COUNT_PER_C - COUNT_REMAIN) / COUNT_PER_C
+ */
+ temp &= ~1;
+ temp += 500000 * temp + (500000 * (buf[7] - buf[6])) / buf[7] - 250000;
+ } else {
+ temp *= 500000;
+ }
+
+ /* convert to uK */
+ return (temp + 273150000);
}
