/* * Copyright (c) 2015, Copyright Per Lindgren * 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. * * This file is part of the Contiki operating system. * * * Author : Per Lindgren * Hacked by: Robert Olsson robert@radio-sensors.com * Created : 2015-11-22 */ #include "contiki.h" #include "dev/temp-sensor.h" #include #define delay_us(us) (_delay_loop_2(1 + (us * F_CPU) / 4000000UL)) const struct sensors_sensor temp_mcu_sensor; /* probe_for_ds18b20 probes for the sensor. Returns 0 on failure, 1 on success * Assumptions: only one sensor on the "1-wire bus", on port WSN_DS18B20_PORT * BUG: THIS CODE DOES NOT WORK AS INTENDED! IT RETURNS "1" EVEN WHEN THERE * IS NO SENSOR CONNECTED. */ uint8_t ds18b20_probe(void) { uint8_t result = 0; /* Reset 1W-bus */ /* Pull PIN low for 480 microseconds (us) * Start with setting bit DS18B20_1_PIN to 0 */ OW_SET_PIN_LOW(); /* then set direction to OUT by setting DS18B20_1_DDR bit to 1 */ OW_SET_OUTPUT(); /* Delay 480 us */ clock_delay_usec(480); /* See if sensor responds. First release the bus and switch to INput mode * by setting DS18B20_1_DDR bit to 0 */ OW_SET_INPUT(); /* Activate internal pull-up by setting pin to HIGH (when in INput mode) * OW_SET_PIN_HIGH(); * Wait for the pin to go HIGH for 64 us */ clock_delay_usec(64); /* Now the sensor, if present, pulls the pin LOW for 60-240 us * Detect 0 on PIND bit DS18B20_1_PIN. Invert the result so a presence * (aka * a 0) sets "result" to 1 (for success) */ result = !OW_GET_PIN_STATE(); /* The sensor releases the pin so it goes HIGH after 240 us, add some for the signal to stabilize, say 300 usecs to be on the safe side? */ if(result) { clock_delay_usec(300); /* Now the bus should be HIGH again */ result = OW_GET_PIN_STATE(); } return result; } /* Write 1 or 0 on the bus */ void write_bit(uint8_t bit) { /* Set pin to 0 */ OW_SET_OUTPUT(); OW_SET_PIN_LOW(); /* Pin should be 0 for at least 1 us */ clock_delay_usec(2); /* If we're writing a 1, let interna pull-up pull the bus high * within 15 us of setting the bus to low */ if(bit) { /* Internal pull-up is activated by setting direction to IN and the * setting the pin to HIGH */ OW_SET_INPUT(); OW_SET_PIN_HIGH(); } /* OK, now the bus is either LOW, or pulled HIGH by the internal pull-up * Let this state remain for 60 us, then release the bus */ clock_delay_usec(60); /* Release the bus */ OW_SET_PIN_HIGH(); OW_SET_INPUT(); /* Allow > 1 us between read/write operations */ clock_delay_usec(2); } /* Read one bit of information from the bus, and return it as 1 or 0 */ uint8_t read_bit(void) { uint8_t bit = 0; /* Set pin to 0 */ OW_SET_OUTPUT(); OW_SET_PIN_LOW(); /* Pin should be 0 for at least 1 us */ clock_delay_usec(2); /* Now read the bus, start by setting in/out direction and activating * internal pull-up resistor */ OW_SET_INPUT(); OW_SET_PIN_HIGH(); /* ds18b20 either keeps the pin down or releases the bus and the * bus then goes high because of the interna pull-up resistor * Check whichever happens before 15 us has passed */ clock_delay_usec(15 - 2 - 1); bit = OW_GET_PIN_STATE(); /* The complete read cycle must last at least 60 us. We have now spent * about 14-15 us in delays, so add another delay to reach >= 60 us */ clock_delay_usec(50); /* Release bus */ OW_SET_PIN_HIGH(); OW_SET_INPUT(); /* Allow > 1 us between read/write operations */ clock_delay_usec(2); return bit ? 1 : 0; } /* Read one byte of information. A byte is read least significant bit first */ uint8_t read_byte(void) { uint8_t result = 0; uint8_t bit; int i; for(i = 0; i < 8; i++) { bit = read_bit(); result += (bit << i); } return result; } /* Write one byte of information. A byte is written least significant bit first */ void write_byte(uint8_t byte) { int i; for(i = 0; i < 8; i++) { write_bit((byte >> i) & 1); } } /* ds18b20_get_temp returns the temperature in "temp" (in degrees celsius) * Returns 0 on failure (and then "temp" is left unchanged * Returns 1 on success, and sets temp */ uint8_t ds18b20_get_temp(double *temp) { uint8_t result = 0; /* Reset bus by probing. Probe returns 1 on success/presence of sensor */ if(ds18b20_probe()) { /* write command "skip rom" since we only have one sensor on the wire! */ write_byte(DS18B20_COMMAND_SKIP_ROM); /* write command to start measurement */ write_byte(DS18B20_COMMAND_START_CONVERSION); /* Wait for conversion to complete. Conversion is 12-bit by default. * Since we have external power to the sensor (ie not in "parasitic power" * mode) the bus is held LOW by the sensor while the conversion is going * on, and then HIGH when conversion is finished. */ OW_SET_INPUT(); int count = 0; while(!OW_GET_PIN_STATE()) { clock_delay_msec(10); count++; /* Longest conversion time is 750 ms (12-bit resolution) * So if count > 80 (for a little margin!), we return -274.0 * which indicates failure to read the temperature. */ if(count > 80) { return 0; } } /* The result is stored in the "scratch pad", a 9 byte memory block. * The first two bytes are the conversion result. Reading the scratch pad * can be terminated by sending a reset signal (but we read all 9 bytes) */ (void)ds18b20_probe(); write_byte(DS18B20_COMMAND_SKIP_ROM); write_byte(DS18B20_COMMAND_READ_SCRATCH_PAD); uint8_t i, sp_arr[9]; for(i = 0; i < 9; i++) { sp_arr[i] = read_byte(); } /* Check CRC, if mismatch, return 0 (failure to read temperature) */ uint8_t crc_cal = crc8_ds18b20(sp_arr, 8); if(crc_cal != sp_arr[8]) { return 0; } /* OK, now decode what the temperature reading is. This code assumes * 12-bit resolution, so this must be modified if the code is modified * to use any other resolution! */ int16_t temp_res; uint8_t temp_lsb = sp_arr[0]; uint8_t temp_msb = sp_arr[1]; temp_res = (int16_t)temp_msb << 8 | temp_lsb; *temp = (double)temp_res * 0.0625; result = 1; } return result; } /* crc8 algorithm for ds18b20 */ /* http://www.miscel.dk/MiscEl/CRCcalculations.html */ uint8_t crc8_ds18b20(uint8_t *buf, uint8_t buf_len) { uint8_t result = 0; uint8_t i, b; for(i = 0; i < buf_len; i++) { result = result ^ buf[i]; for(b = 1; b < 9; b++) { if(result & 0x1) { result = (result >> 1) ^ 0x8C; } else { result = result >> 1; } } } return result; } static int value(int type) { double t; int ret; ret = ds18b20_get_temp(&t); /* Return temp multiplied by 100 for two decimals */ if(ret) return (int) (t * 100); /* Error return largest negative value */ return 0x8000; } static int configure(int type, int c) { ds18b20_probe(); return 0; } static int status(int type) { return 1; } SENSORS_SENSOR(temp_sensor, TEMP_SENSOR, value, configure, status);