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* Device driver for the SHT1x on the Tmote sky.

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bg- 2007-04-04 12:48:50 +00:00
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324
platform/sky/dev/sht11.c Normal file
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/*
* Copyright (c) 2007, Swedish Institute of Computer Science
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)$Id: sht11.c,v 1.1 2007/04/04 12:48:50 bg- Exp $
*/
/*
* Device driver for the Sensirion SHT1x/SHT7x family of humidity and
* temperature sensors.
*/
#include <stdio.h>
#include <io.h>
#include <dev/sht11.h>
/*
* SHT11_SDA P1.5
* SHT11_SCL P1.6
* SHT11_PWR P1.7
*/
#define SDA 5
#define SCL 6
#define PWR 7
/* Confusingly similar to I2C but not quite :-( */
#define I2C_PxDIR P1DIR
#define I2C_PxIN P1IN
#define I2C_PxOUT P1OUT
#define I2C_PxSEL P1SEL
#define SDA_0() (I2C_PxDIR |= BV(SDA)) /* SDA Output=0 */
#define SDA_1() (I2C_PxDIR &= ~BV(SDA)) /* SDA Input */
#define SDA_IS_1 (I2C_PxIN & BV(SDA))
#define SCL_0() (I2C_PxOUT &= ~BV(SCL)) /* SCL Output=0 */
#define SCL_1() (I2C_PxOUT |= BV(SCL)) /* SCL Output=1 */
/* adr command r/w */
#define STATUS_REG_W 0x06 /* 000 0011 0 */
#define STATUS_REG_R 0x07 /* 000 0011 1 */
#define MEASURE_TEMP 0x03 /* 000 0001 1 */
#define MEASURE_HUMI 0x05 /* 000 0010 1 */
#define RESET 0x1e /* 000 1111 0 */
/* This can probably be reduced to 250ns according to data sheet. */
#define delay_400ns() _NOP()
static void
sstart(void)
{
SDA_1(); SCL_0();
delay_400ns();
SCL_1();
delay_400ns();
SDA_0();
delay_400ns();
SCL_0();
delay_400ns();
SCL_1();
delay_400ns();
SDA_1();
delay_400ns();
SCL_0();
}
static void
sreset(void)
{
int i;
SDA_1(); SCL_0();
for (i = 0; i < 9 ; i++) {
SCL_1();
delay_400ns();
SCL_0();
}
sstart(); /* Start transmission, why??? */
}
/*
* Return true if we received an ACK.
*/
static int
swrite(unsigned _c)
{
unsigned char c = _c;
int i;
int ret;
for (i = 0; i < 8; i++, c <<= 1) {
if (c & 0x80)
SDA_1();
else
SDA_0();
SCL_1();
delay_400ns();
SCL_0();
}
SDA_1();
SCL_1();
delay_400ns();
ret = !SDA_IS_1;
SCL_0();
return ret;
}
static unsigned
sread(int send_ack)
{
int i;
unsigned char c = 0x00;
SDA_1();
for (i = 0; i < 8; i++) {
c <<= 1;
SCL_1();
delay_400ns();
if (SDA_IS_1)
c |= 0x1;
SCL_0();
}
if (send_ack)
SDA_0();
SCL_1();
delay_400ns();
SCL_0();
SDA_1(); /* Release SDA */
return c;
}
#define CRC_CHECK
#ifdef CRC_CHECK
static unsigned char
rev8bits(unsigned char v)
{
unsigned char r = v;
int s = 7;
for (v >>= 1; v; v >>= 1) {
r <<= 1;
r |= v & 1;
s--;
}
r <<= s; /* Shift when v's highest bits are zero */
return r;
}
/* BEWARE: Bit reversed CRC8 using polynomial ^8 + ^5 + ^4 + 1 */
static unsigned
crc8_add(unsigned acc, unsigned byte)
{
int i;
acc ^= byte;
for (i = 0; i < 8; i++)
if (acc & 0x80)
acc = (acc << 1) ^ 0x31;
else
acc <<= 1;
return acc & 0xff;
}
#endif /* CRC_CHECK */
void
sht11_init(void)
{
/*
* SCL Output={0,1}
* SDA 0: Output=0
* 1: Input and pull-up (Output=0)
*/
P1OUT |= BV(PWR);
P1OUT &= ~(BV(SDA) | BV(SCL));
P1DIR |= BV(PWR) | BV(SCL);
}
/*
* Only commands MEASURE_HUMI or MEASURE_TEMP!
*/
static unsigned
scmd(unsigned cmd)
{
unsigned long n;
if (cmd != MEASURE_HUMI && cmd != MEASURE_TEMP)
return -1;
sstart(); /* Start transmission */
if (!swrite(cmd))
goto fail;
for (n = 0; n < 250000; n++)
if (!SDA_IS_1) {
unsigned t0, t1, rcrc;
t0 = sread(1);
t1 = sread(1);
rcrc = sread(0);
#ifdef CRC_CHECK
{
unsigned crc;
crc = crc8_add(0x0, cmd);
crc = crc8_add(crc, t0);
crc = crc8_add(crc, t1);
if (crc != rev8bits(rcrc))
goto fail;
}
#endif
return (t0 << 8) | t1;
}
fail:
sreset();
return -1;
}
unsigned
sht11_temp(void)
{
return scmd(MEASURE_TEMP);
}
unsigned
sht11_humidity(void)
{
return scmd(MEASURE_HUMI);
}
#if 0 /* But ok! */
unsigned
sget_sreg(void)
{
unsigned sreg, rcrc;
sstart(); /* Start transmission */
if (!swrite(STATUS_REG_R))
goto fail;
sreg = sread(1);
rcrc = sread(0);
#ifdef CRC_CHECK
{
unsigned crc;
crc = crc8_add(0x0, STATUS_REG_R);
crc = crc8_add(crc, sreg);
if (crc != rev8bits(rcrc))
goto fail;
}
#endif
return sreg;
fail:
sreset();
return -1;
}
#endif
#if 0
unsigned
sset_sreg(unsigned sreg)
{
sstart(); /* Start transmission */
if (!swrite(STATUS_REG_W))
goto fail;
if (!swrite(sreg))
goto fail;
return 0;
fail:
sreset();
return -1;
}
#endif
#if 0
int
sht11_reset(void)
{
sstart(); /* Start transmission */
if (!swrite(RESET))
goto fail;
return 0;
fail:
sreset();
return -1;
}
#endif

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platform/sky/dev/sht11.h Normal file
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/*
* Copyright (c) 2007, Swedish Institute of Computer Science
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)$Id: sht11.h,v 1.1 2007/04/04 12:48:50 bg- Exp $
*/
#ifndef SHT11_H
#define SHT11_H
void sht11_init(void);
unsigned sht11_temp(void);
unsigned sht11_humidity(void);
#endif /* SHT11_H */