Benoit Agache
c
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();
+}