/* * 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 #include #include /* * 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