diff options
| author | Alexander Yurchenko <grange@cvs.openbsd.org> | 2006-12-20 14:47:00 +0000 |
|---|---|---|
| committer | Alexander Yurchenko <grange@cvs.openbsd.org> | 2006-12-20 14:47:00 +0000 |
| commit | c40a742c0f3c3fcde40e94a1b2e579823acb07e3 (patch) | |
| tree | 395c74adda6a229ffa8e2b903d9ebc7f86ac0b23 /sys/dev | |
| parent | 1b6bcdace1e102b6acd3c88f5d7fd1c6dbbb6f09 (diff) | |
Implement high resolution temperature measuring.
Based on the diff provided by aaron@linville.org in PR 5314.
Diffstat (limited to 'sys/dev')
| -rw-r--r-- | sys/dev/onewire/owtemp.c | 33 |
1 files changed, 29 insertions, 4 deletions
diff --git a/sys/dev/onewire/owtemp.c b/sys/dev/onewire/owtemp.c index 26ea09884c2..cd561a54c69 100644 --- a/sys/dev/onewire/owtemp.c +++ b/sys/dev/onewire/owtemp.c @@ -1,4 +1,4 @@ -/* $OpenBSD: owtemp.c,v 1.4 2006/10/01 11:43:40 grange Exp $ */ +/* $OpenBSD: owtemp.c,v 1.5 2006/12/20 14:46:59 grange Exp $ */ /* * Copyright (c) 2006 Alexander Yurchenko <grange@openbsd.org> @@ -32,9 +32,19 @@ #include <dev/onewire/onewirereg.h> #include <dev/onewire/onewirevar.h> +/* Commands */ #define DS1920_CMD_CONVERT 0x44 #define DS1920_CMD_READ_SCRATCHPAD 0xbe +/* Scratchpad layout */ +#define DS1920_SP_TEMP_LSB 0 +#define DS1920_SP_TEMP_MSB 1 +#define DS1920_SP_TH 2 +#define DS1920_SP_TL 3 +#define DS1920_SP_COUNT_REMAIN 6 +#define DS1920_SP_COUNT_PERC 7 +#define DS1920_SP_CRC 8 + struct owtemp_softc { struct device sc_dev; @@ -124,6 +134,8 @@ owtemp_update(void *arg) { struct owtemp_softc *sc = arg; u_int8_t data[9]; + u_int16_t temp; + int count_perc, count_remain, val; rw_enter_write(&sc->sc_lock); onewire_lock(sc->sc_onewire, 0); @@ -151,9 +163,22 @@ owtemp_update(void *arg) */ onewire_write_byte(sc->sc_onewire, DS1920_CMD_READ_SCRATCHPAD); onewire_read_block(sc->sc_onewire, data, 9); - if (onewire_crc(data, 8) == data[8]) { - sc->sc_sensor.value = 273150000 + - (int)((u_int16_t)data[1] << 8 | data[0]) * 500000; + if (onewire_crc(data, 8) == data[DS1920_SP_CRC]) { + temp = data[DS1920_SP_TEMP_MSB] << 8 | + data[DS1920_SP_TEMP_LSB]; + count_perc = data[DS1920_SP_COUNT_PERC]; + count_remain = data[DS1920_SP_COUNT_REMAIN]; + + if (count_perc != 0) { + /* High resolution algorithm */ + temp &= ~0x0001; + val = temp * 500000 - 250000 + + ((count_perc - count_remain) * 1000000) / + count_perc; + } else { + val = temp * 500000; + } + sc->sc_sensor.value = 273150000 + val; } done: |