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();
+}