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