Library for reading temperature from DS1820, DS18B20 and DS1822
Dependents: heatmap BLE_Temperature BLE_Temperature_Exercise F334andDS18B20 ... more
Fork of DS1820 by
HelloWorld: http://mbed.org/users/Sissors/code/DS1820_HelloWorld/
Library should currently work on all mbed targets, let me know if there is an issue. First however make sure you have latest version of mbed library and this library.
DS1820.cpp
- Committer:
- Michael_
- Date:
- 2010-12-19
- Revision:
- 0:61d83318f2d6
- Child:
- 1:6a427f54e82c
File content as of revision 0:61d83318f2d6:
#include "DS1820.h" #include "mbed.h" // Global variables shared between all DS1820 objects bool DS1820_done_flag; int DS1820_last_descrepancy; char DS1820_search_ROM[8]; DS1820::DS1820 (PinName data_pin, PinName power_pin) : _datapin(data_pin), _parasitepin(power_pin) { int byte_counter; _parasite_power = true; for(byte_counter=0;byte_counter<8;byte_counter++) ROM[byte_counter] = 0xFF; for(byte_counter=0;byte_counter<9;byte_counter++) RAM[byte_counter] = 0x00; } DS1820::DS1820 (PinName data_pin) : _datapin(data_pin), _parasitepin(NC) { int byte_counter; _parasite_power = false; for(byte_counter=0;byte_counter<8;byte_counter++) ROM[byte_counter] = 0xFF; for(byte_counter=0;byte_counter<9;byte_counter++) RAM[byte_counter] = 0x00; } bool DS1820::onewire_reset() { // This will return false if no devices are present on the data bus bool presence=false; _datapin.output(); _datapin = 0; // bring low for 500 us wait_us(500); _datapin.input(); // let the data line float high wait_us(90); // wait 90us if (_datapin.read()==0) // see if any devices are pulling the data line low presence=true; wait_us(410); return presence; } void DS1820::onewire_bit_out (bool bit_data) { _datapin.output(); _datapin = 0; wait_us(5); if (bit_data) { _datapin.input(); // bring data line high wait_us(55); } else { wait_us(55); // keep data line low _datapin.input(); } } void DS1820::onewire_byte_out(char data) { // output data character (least sig bit first). int n; for (n=0; n<8; n++) { onewire_bit_out(data & 0x01); data = data >> 1; // now the next bit is in the least sig bit position. } } bool DS1820::onewire_bit_in() { bool answer; _datapin.output(); _datapin = 0; wait_us(5); _datapin.input(); wait_us(5); answer = _datapin.read(); wait_us(50); return answer; } char DS1820::onewire_byte_in() { // read byte, least sig byte first char answer = 0x00; int i; for (i=0; i<8; i++) { answer = answer >> 1; // shift over to make room for the next bit if (onewire_bit_in()) answer = answer | 0x80; // if the data port is high, make this bit a 1 } return answer; } bool DS1820::search_ROM() { return search_ROM_routine(0xF0); // Search ROM command } bool DS1820::search_alarm() { return search_ROM_routine(0xEC); // Search Alarm command } bool DS1820::search_ROM_routine(char command) { extern bool DS1820_done_flag; extern int DS1820_last_descrepancy; extern char DS1820_search_ROM[8]; int descrepancy_marker, ROM_bit_index; bool return_value, Bit_A, Bit_B; char byte_counter, bit_mask; return_value=false; if (!DS1820_done_flag) { if (!onewire_reset()) { DS1820_last_descrepancy = 0; // no devices present } else { ROM_bit_index=1; descrepancy_marker=0; onewire_byte_out(command); // Search ROM command or Search Alarm command byte_counter = 0; bit_mask = 0x01; while (ROM_bit_index<=64) { Bit_A = onewire_bit_in(); Bit_B = onewire_bit_in(); if (Bit_A & Bit_B) { descrepancy_marker = 0; // data read error, this should never happen ROM_bit_index = 0xFF; } else { if (Bit_A | Bit_B) { // Set ROM bit to Bit_A if (Bit_A) { DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one } else { DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero } } else { // both bits A and B are low, so there are two or more devices present if ( ROM_bit_index == DS1820_last_descrepancy ) { DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one } else { if ( ROM_bit_index > DS1820_last_descrepancy ) { DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero descrepancy_marker = ROM_bit_index; } else { if (( DS1820_search_ROM[byte_counter] & bit_mask) == 0x00 ) descrepancy_marker = ROM_bit_index; } } } onewire_bit_out (DS1820_search_ROM[byte_counter] & bit_mask); ROM_bit_index++; if (bit_mask & 0x80) { byte_counter++; bit_mask = 0x01; } else { bit_mask = bit_mask << 1; } } } DS1820_last_descrepancy = descrepancy_marker; if (ROM_bit_index != 0xFF) { for(byte_counter=0;byte_counter<8;byte_counter++) ROM[byte_counter] = DS1820_search_ROM[byte_counter]; return_value = true; } } if (DS1820_last_descrepancy == 0) DS1820_done_flag = true; } return return_value; } void DS1820::search_ROM_setup() { extern bool DS1820_done_flag; extern int DS1820_last_descrepancy; extern char DS1820_search_ROM[8]; DS1820_done_flag = false; DS1820_last_descrepancy = 0; int i; for (i=0; i<8; i++) DS1820_search_ROM[i]=0x00; } void DS1820::read_ROM() { // NOTE: This command can only be used when there is one DS1820 on the bus. If this command // is used when there is more than one slave present on the bus, a data collision will occur // when all the DS1820s attempt to respond at the same time. int i; onewire_reset(); onewire_byte_out(0x33); // Read ROM id for (i=0; i<8; i++) ROM[i]=onewire_byte_in(); } void DS1820::match_ROM() { // Used to select a specific device int i; onewire_reset(); onewire_byte_out( 0x55); //Match ROM command for (i=0;i<8;i++) onewire_byte_out(ROM[i]); } void DS1820::skip_ROM() { onewire_reset(); onewire_byte_out(0xCC); // Skip ROM command } bool DS1820::ROM_checksum_error() { char CRC=0x00; int i; for(i=0;i<7;i++) // Only going to shift the lower 7 bytes CRC = CRC_byte(CRC, ROM[i]); // After 7 bytes CRC should equal the 8th byte (ROM CRC) return (CRC!=ROM[7]); // will return true if there is a CRC checksum error } bool DS1820::RAM_checksum_error() { char CRC=0x00; int i; read_RAM(); for(i=0;i<8;i++) // Only going to shift the lower 8 bytes CRC = CRC_byte(CRC, RAM[i]); // After 8 bytes CRC should equal the 9th byte (RAM CRC) return (CRC!=RAM[8]); // will return true if there is a CRC checksum error } char DS1820::CRC_byte (char CRC, char byte ) { int j; for(j=0;j<8;j++) { if ((byte & 0x01 ) ^ (CRC & 0x01)) { // DATA ^ LSB CRC = 1 CRC = CRC>>1; // Set the MSB to 1 CRC = CRC | 0x80; // Check bit 3 if (CRC & 0x04) { CRC = CRC & 0xFB; // Bit 3 is set, so clear it } else { CRC = CRC | 0x04; // Bit 3 is clear, so set it } // Check bit 4 if (CRC & 0x08) { CRC = CRC & 0xF7; // Bit 4 is set, so clear it } else { CRC = CRC | 0x08; // Bit 4 is clear, so set it } } else { // DATA ^ LSB CRC = 0 CRC = CRC>>1; // clear MSB CRC = CRC & 0x7F; // No need to check bits, with DATA ^ LSB CRC = 0, they will remain unchanged } byte = byte>>1; } return CRC; } void DS1820::convert_temperature(devices device) { // Convert temperature into scratchpad RAM for all devices at once if (device==all_devices) skip_ROM(); // Skip ROM command, will convert for ALL devices else match_ROM(); onewire_byte_out( 0x44); // perform temperature conversion if (_parasite_power) _parasitepin = 1; // Parasite power strong pullup wait_ms(750); if (_parasite_power) _parasitepin = 0; } void DS1820::read_RAM() { // This will copy the DS1820's 9 bytes of RAM data // into the objects RAM array. Functions that use // RAM values will automaticly call this procedure. int i; match_ROM(); // Select this device onewire_byte_out( 0xBE); //Read Scratchpad command for(i=0;i<9;i++) { RAM[i] = onewire_byte_in(); } } int DS1820::read_scratchpad() { int answer; read_RAM(); answer = (RAM[2]<<8) + RAM[3]; return answer; } void DS1820::write_scratchpad(int data) { RAM[3] = data; RAM[2] = data>>8; match_ROM(); onewire_byte_out(0x4E); // Copy scratchpad into DS1820 ram memory onewire_byte_out(RAM[2]); // T(H) onewire_byte_out(RAM[3]); // T(L) } void DS1820::store_scratchpad(devices device) { if (device==all_devices) skip_ROM(); // Skip ROM command, will store for ALL devices else match_ROM(); onewire_byte_out(0x48); // Write scratchpad into E2 command if (_parasite_power) _parasitepin=1; wait_ms(10); // Parasite power strong pullup for 10ms if (_parasite_power) _parasitepin=0; } int DS1820::recall_scratchpad(devices device) { // This copies the E2 values into the DS1820's memory. // If you specify all_devices this will return zero, otherwise // it will return the value of the scratchpad memory. int answer=0; if (device==all_devices) skip_ROM(); // Skip ROM command, will recall for ALL devices else match_ROM(); onewire_byte_out(0xB8); // Recall E2 data to scratchpad command wait_ms(10); // not sure I like polling for completion // it could cause an infinite loop if (device==DS1820::this_device) { read_RAM(); answer = read_scratchpad(); } return answer; } float DS1820::temperature(char scale) { // The data specs state that count_per_degree should be 0x10 (16), I found my devices // to have a count_per_degree of 0x4B (75). With the standard resolution of 1/2 deg C // this allowed an expanded resolution of 1/150th of a deg C. I wouldn't rely on this // being super acurate, but it does allow for a smooth display in the 1/10ths of a // deg C or F scales. float answer, remaining_count, count_per_degree; int reading; read_RAM(); reading = (RAM[1] << 8) + RAM[0]; if (reading & 0x8000) { // negative degrees C reading = 0-((reading ^ 0xffff) + 1); // 2's comp then convert to signed int } remaining_count = RAM[6]; count_per_degree = RAM[7]; answer = reading +0.0; answer = answer - 0.25 + (count_per_degree - remaining_count) / count_per_degree; if (scale=='C' or scale=='c') answer = answer / 2.0; else // Convert to deg F answer = answer * 9.0 / 10.0 + 32.0; return answer; } bool DS1820::read_power_supply(devices device) { // This will return true if the device (or all devices) are Vcc powered // This will return false if the device (or ANY device) is parasite powered if (device==all_devices) skip_ROM(); // Skip ROM command, will poll for any device using parasite power else match_ROM(); onewire_byte_out(0xB4); // Read power supply command return onewire_bit_in(); }