SSL multi-sensor
Diff: DS1820.cpp
- Revision:
- 0:61d83318f2d6
- Child:
- 1:6a427f54e82c
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/DS1820.cpp Sun Dec 19 05:40:28 2010 +0000 @@ -0,0 +1,357 @@ +#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(); +}