420 lines
13 KiB
C++
420 lines
13 KiB
C++
/*
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* Dallas' DS1820 family temperature sensor.
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* This library depends on the OneWire library (Dallas' 1-Wire bus protocol implementation)
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* available at <http://developer.mbed.org/users/hudakz/code/OneWire/>
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*
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* Example of use:
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*
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* Single sensor.
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*
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* #include "mbed.h"
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* #include "DS1820.h"
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*
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* Serial pc(USBTX, USBRX);
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* DigitalOut led(LED1);
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* OneWire oneWire(D8); // substitute D8 with actual mbed pin name connected 1-wire bus
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* float temp = 0;
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* int result = 0;
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*
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* int main()
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* {
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* pc.printf("\r\n--Starting--\r\n");
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* if (ds1820.begin()) {
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* while (1) {
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* ds1820.startConversion(); // start temperature conversion from analog to digital
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* ThisThread::sleep_for(1000);// let DS1820 complete the temperature conversion
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* result = ds1820.read(temp); // read temperature from DS1820 and perform cyclic redundancy check (CRC)
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* switch (result) {
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* case 0: // no errors -> 'temp' contains the value of measured temperature
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* pc.printf("temp = %3.1f%cC\r\n", temp, 176);
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* break;
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*
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* case 1: // no sensor present -> 'temp' is not updated
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* pc.printf("no sensor present\n\r");
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* break;
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*
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* case 2: // CRC error -> 'temp' is not updated
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* pc.printf("CRC error\r\n");
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* }
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*
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* led = !led;
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* }
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* }
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* else
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* pc.printf("No DS1820 sensor found!\r\n");
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* }
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*
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*
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* More sensors connected to the same 1-wire bus.
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*
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* #include "mbed.h"
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* #include "DS1820.h"
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*
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* #define SENSORS_COUNT 64 // number of DS1820 sensors to be connected to the 1-wire bus (max 256)
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*
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* Serial pc(USBTX, USBRX);
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* DigitalOut led(LED1);
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* OneWire oneWire(D8); // substitute D8 with actual mbed pin name connected to the DS1820 data pin
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* DS1820* ds1820[SENSORS_COUNT];
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* int sensors_found = 0; // counts the actually found DS1820 sensors
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* float temp = 0;
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* int result = 0;
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*
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* int main() {
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* int i = 0;
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*
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* pc.printf("\r\n Starting \r\n");
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* //Enumerate (i.e. detect) DS1820 sensors on the 1-wire bus
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* for(i = 0; i < SENSORS_COUNT; i++) {
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* ds1820[i] = new DS1820(&oneWire);
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* if(!ds1820[i]->begin()) {
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* delete ds1820[i];
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* break;
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* }
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* }
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*
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* sensors_found = i;
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*
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* if (sensors_found == 0) {
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* pc.printf("No DS1820 sensor found!\r\n");
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* return -1;
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* }
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* else
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* pc.printf("Found %d sensors.\r\n", sensors_found);
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*
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* while(1) {
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* pc.printf("-------------------\r\n");
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* for(i = 0; i < sensors_found; i++)
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* ds1820[i]->startConversion(); // start temperature conversion from analog to digital
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* ThisThread::sleep_for(1000); // let DS1820s complete the temperature conversion
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* for(int i = 0; i < sensors_found; i++) {
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* if(ds1820[i]->isPresent())
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* pc.printf("temp[%d] = %3.1f%cC\r\n", i, ds1820[i]->read(), 176); // read temperature
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* }
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* }
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* }
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*
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*/
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#include "DS1820.h"
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#define DEBUG 0
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//* Initializing static members
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uint8_t DS1820::lastAddr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
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/**
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* @brief Constructs a generic DS1820 sensor
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* @note begin() must be called to detect and initialize the actual model
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* @param pin: Name of data pin
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* @retval
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*/
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DS1820::DS1820(PinName pin, int sample_point_us /* = 13 */) {
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oneWire = new OneWire(pin, sample_point_us);
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present = false;
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model_s = false;
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}
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/**
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* @brief Constructs a generic DS1820 sensor
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* @note begin() must be called to detect and initialize the actual model
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* @param pin: Name of data pin
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* @retval
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*/
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DS1820::DS1820(OneWire* wire) :
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oneWire(wire) {
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present = false;
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model_s = false;
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}
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/**
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* @brief Detects and initializes the actual DS1820 model
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* @note
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* @param
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* @retval true: if a DS1820 family sensor was detected and initialized
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false: otherwise
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*/
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bool DS1820::begin(void) {
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#if DEBUG
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printf("lastAddr =");
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for(uint8_t i = 0; i < 8; i++) {
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printf(" %x", lastAddr[i]);
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}
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printf("\r\n");
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#endif
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if(!oneWire->search(lastAddr)) {
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#if DEBUG
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printf("No addresses.\r\n");
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#endif
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oneWire->reset_search();
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ThisThread::sleep_for(250);
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return false;
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}
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for (int i = 0; i < 8; i++)
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addr[i] = lastAddr[i];
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#if DEBUG
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printf("ROM =");
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for(uint8_t i = 0; i < 8; i++) {
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printf(" %x", addr[i]);
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}
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printf("\r\n");
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#endif
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if(OneWire::crc8(addr, 7) == addr[7]) {
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present = true;
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// the first ROM byte indicates which chip
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switch(addr[0]) {
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case 0x10:
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model_s = true;
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#if DEBUG
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printf("DS18S20 or old DS1820\r\n");
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#endif
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break;
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case 0x28:
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model_s = false;
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#if DEBUG
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printf("DS18B20\r\n");
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#endif
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break;
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case 0x22:
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model_s = false;
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#if DEBUG
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printf("DS1822\r\n");
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#endif
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break;
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default:
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present = false;
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#if DEBUG
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printf("Device doesn't belong to the DS1820 family\r\n");
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#endif
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return false;
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}
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return true;
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}
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else {
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#if DEBUG
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printf("Invalid CRC!\r\n");
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#endif
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return false;
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}
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}
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/**
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* @brief Informs about presence of a DS1820 sensor.
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* @note begin() shall be called before using this function
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* if a generic DS1820 instance was created by the user.
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* No need to call begin() for a specific DS1820 instance.
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* @param
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* @retval true: when a DS1820 sensor is present
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* false: otherwise
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*/
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bool DS1820::isPresent(void) {
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return present;
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}
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/**
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* @brief Sets temperature-to-digital conversion resolution.
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* @note The configuration register allows the user to set the resolution
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* of the temperature-to-digital conversion to 9, 10, 11, or 12 bits.
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* Defaults to 12-bit resolution for DS18B20.
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* DS18S20 allows only 9-bit resolution.
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* @param res: Resolution of the temperature-to-digital conversion in bits.
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* @retval
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*/
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void DS1820::setResolution(uint8_t res) {
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// keep resolution within limits
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if(res > 12)
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res = 12;
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if(res < 9)
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res = 9;
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if(model_s)
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res = 9;
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oneWire->reset();
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oneWire->select(addr);
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oneWire->write_byte(0xBE); // to read Scratchpad
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for(uint8_t i = 0; i < 9; i++) // read Scratchpad bytes
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data[i] = oneWire->read_byte();
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data[4] |= (res - 9) << 5; // update configuration byte (set resolution)
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oneWire->reset();
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oneWire->select(addr);
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oneWire->write_byte(0x4E); // to write into Scratchpad
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for(uint8_t i = 2; i < 5; i++) // write three bytes (2nd, 3rd, 4th) into Scratchpad
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oneWire->write_byte(data[i]);
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}
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/**
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* @brief Starts temperature conversion
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* @note The time to complete the converion depends on the selected resolution:
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* 9-bit resolution -> max conversion time = 93.75ms
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* 10-bit resolution -> max conversion time = 187.5ms
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* 11-bit resolution -> max conversion time = 375ms
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* 12-bit resolution -> max conversion time = 750ms
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* @param
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* @retval
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*/
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void DS1820::startConversion(void) {
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if(present) {
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oneWire->reset();
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oneWire->select(addr);
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oneWire->write_byte(0x44); //start temperature conversion
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}
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}
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/**
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* @brief Reads temperature from the chip's Scratchpad
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* @note
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* @param
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* @retval Floating point temperature value
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*/
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float DS1820::read(void) {
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if(present) {
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oneWire->reset();
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oneWire->select(addr);
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oneWire->write_byte(0xBE); // to read Scratchpad
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for(uint8_t i = 0; i < 9; i++) // reading scratchpad registers
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data[i] = oneWire->read_byte();
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// Convert the raw bytes to a 16-bit unsigned value
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uint16_t* p_word = reinterpret_cast < uint16_t * > (&data[0]);
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#if DEBUG
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printf("raw = %#x\r\n", *p_word);
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#endif
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if(model_s) {
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*p_word = *p_word << 3; // 9-bit resolution
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if(data[7] == 0x10) {
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// "count remain" gives full 12-bit resolution
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*p_word = (*p_word & 0xFFF0) + 12 - data[6];
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}
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}
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else {
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uint8_t cfg = (data[4] & 0x60); // default 12-bit resolution
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// at lower resolution, the low bits are undefined, so let's clear them
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if(cfg == 0x00)
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*p_word = *p_word &~7; // 9-bit resolution
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else
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if(cfg == 0x20)
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*p_word = *p_word &~3; // 10-bit resolution
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else
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if(cfg == 0x40)
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*p_word = *p_word &~1; // 11-bit resolution
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}
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// Convert the raw bytes to a 16-bit signed fixed point value :
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// 1 sign bit, 7 integer bits, 8 fractional bits (two’s compliment
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// and the LSB of the 16-bit binary number represents 1/256th of a unit).
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*p_word = *p_word << 4;
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// Convert to floating point value
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return(toFloat(*p_word));
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}
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else
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return 0;
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}
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/**
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* @brief Reads temperature from chip's scratchpad.
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* @note Verifies data integrity by calculating cyclic redundancy check (CRC).
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* If the calculated CRC dosn't match the one stored in chip's scratchpad register
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* the temperature variable is not updated and CRC error code is returned.
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* @param temp: The temperature variable to be updated by this routine.
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* (It's passed as reference to floating point.)
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* @retval error code:
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* 0 - no errors ('temp' contains the temperature measured)
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* 1 - sensor not present ('temp' is not updated)
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* 2 - CRC error ('temp' is not updated)
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*/
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uint8_t DS1820::read(float& temp) {
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if(present) {
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oneWire->reset();
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oneWire->select(addr);
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oneWire->write_byte(0xBE); // to read Scratchpad
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for(uint8_t i = 0; i < 9; i++) // reading scratchpad registers
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data[i] = oneWire->read_byte();
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if(oneWire->crc8(data, 8) != data[8]) // if calculated CRC does not match the stored one
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{
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#if DEBUG
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for(uint8_t i = 0; i < 9; i++)
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printf("data[%d]=0x%.2x\r\n", i, data[i]);
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#endif
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return 2; // return with CRC error
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}
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// Convert the raw bytes to a 16bit unsigned value
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uint16_t* p_word = reinterpret_cast < uint16_t * > (&data[0]);
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#if DEBUG
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printf("raw = %#x\r\n", *p_word);
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#endif
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if(model_s) {
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*p_word = *p_word << 3; // 9 bit resolution, max conversion time = 750ms
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if(data[7] == 0x10) {
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// "count remain" gives full 12 bit resolution
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*p_word = (*p_word & 0xFFF0) + 12 - data[6];
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}
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// Convert the raw bytes to a 16bit signed fixed point value :
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// 1 sign bit, 7 integer bits, 8 fractional bits (two's compliment
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// and the LSB of the 16bit binary number represents 1/256th of a unit).
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*p_word = *p_word << 4;
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// Convert to floating point value
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temp = toFloat(*p_word);
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return 0; // return with no errors
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}
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else {
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uint8_t cfg = (data[4] & 0x60); // default 12bit resolution, max conversion time = 750ms
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// at lower resolution, the low bits are undefined, so let's clear them
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if(cfg == 0x00)
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*p_word = *p_word &~7; // 9bit resolution, max conversion time = 93.75ms
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else
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if(cfg == 0x20)
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*p_word = *p_word &~3; // 10bit resolution, max conversion time = 187.5ms
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else
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if(cfg == 0x40)
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*p_word = *p_word &~1; // 11bit resolution, max conversion time = 375ms
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// Convert the raw bytes to a 16bit signed fixed point value :
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// 1 sign bit, 7 integer bits, 8 fractional bits (two's complement
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// and the LSB of the 16bit binary number represents 1/256th of a unit).
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*p_word = *p_word << 4;
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// Convert to floating point value
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temp = toFloat(*p_word);
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return 0; // return with no errors
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}
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}
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else
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return 1; // error, sensor is not present
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}
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/**
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* @brief Converts a 16-bit signed fixed point value to floating point value
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* @note The 16-bit unsigned integer represnts actually
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* a 16-bit signed fixed point value:
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* 1 sign bit, 7 integer bits, 8 fractional bits (two’s complement
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* and the LSB of the 16-bit binary number represents 1/256th of a unit).
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* @param 16-bit unsigned integer
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* @retval Floating point value
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*/
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float DS1820::toFloat(uint16_t word) {
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if(word & 0x8000)
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return (-float(uint16_t(~word + 1)) / 256.0f);
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else
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return (float(word) / 256.0f);
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}
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