Chris Roberts
Library for MAX31850 thermocouple temperature sensor
Diff: MAX31850.cpp
- Revision:
- 0:5530bf2d0e94
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/MAX31850.cpp Wed Jan 23 23:44:57 2019 +0000
@@ -0,0 +1,364 @@
+#include "MAX31850.h"
+
+Serial pc(USBTX, USBRX);
+
+#define ONEWIRE_INPUT(pin) pin->input()
+#define ONEWIRE_OUTPUT(pin) pin->output()
+#define ONEWIRE_INIT(pin)
+
+LinkedList<node> MAX31850::probes;
+
+
+MAX31850::MAX31850 (PinName data_pin, PinName power_pin, bool power_polarity) : _datapin(data_pin), _parasitepin(power_pin) {
+ int byte_counter;
+ _power_polarity = power_polarity;
+
+ _power_mosfet = power_pin != NC;
+
+ for(byte_counter=0;byte_counter<9;byte_counter++)
+ scratchpad[byte_counter] = 0x00;
+
+ ONEWIRE_INIT((&_datapin));
+
+ if (!unassignedProbe(&_datapin, _ROM))
+ error("No unassigned MAX31850 found!\n");
+ else {
+ _datapin.input();
+ probes.append(this);
+ _parasite_power = false; //only set up to use external power right now
+ }
+}
+
+MAX31850::~MAX31850 (void) {
+ node *tmp;
+ for(int i=1; i<=probes.length(); i++)
+ {
+ tmp = probes.pop(i);
+ if (tmp->data == this)
+ probes.remove(i);
+ }
+}
+
+
+bool MAX31850::onewire_reset(DigitalInOut *pin) {
+// This will return false if no devices are present on the data bus
+ bool presence=false;
+ ONEWIRE_OUTPUT(pin);
+ pin->write(0); // bring low for 500 us
+ wait_us(500);
+ ONEWIRE_INPUT(pin); // let the data line float high
+ wait_us(90); // wait 90us
+ if (pin->read()==0) // see if any devices are pulling the data line low
+ presence=true;
+ wait_us(410);
+ return presence;
+}
+
+void MAX31850::onewire_bit_out (DigitalInOut *pin, bool bit_data) {
+ ONEWIRE_OUTPUT(pin);
+ pin->write(0);
+ wait_us(3); // DXP modified from 5
+ if (bit_data) {
+ pin->write(1); // bring data line high
+ wait_us(55);
+ } else {
+ wait_us(55); // keep data line low
+ pin->write(1);
+ wait_us(10); // DXP added to allow bus to float high before next bit_out
+ }
+}
+
+void MAX31850::onewire_byte_out(char data) { // output data character (least sig bit first).
+ int n;
+ for (n=0; n<8; n++) {
+ onewire_bit_out(&this->_datapin, data & 0x01);
+ data = data >> 1; // now the next bit is in the least sig bit position.
+ }
+}
+
+bool MAX31850::onewire_bit_in(DigitalInOut *pin) {
+ bool answer;
+ ONEWIRE_OUTPUT(pin);
+ pin->write(0);
+ wait_us(3); // DXP modified from 5
+ ONEWIRE_INPUT(pin);
+ wait_us(10); // DXP modified from 5
+ answer = pin->read();
+ wait_us(45); // DXP modified from 50
+ return answer;
+}
+
+char MAX31850::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(&this->_datapin))
+ answer = answer | 0x80; // if the data port is high, make this bit a 1
+ }
+ return answer;
+}
+
+bool MAX31850::unassignedProbe(PinName pin) {
+ DigitalInOut _pin(pin);
+ ONEWIRE_INIT((&_pin));
+ char ROM_address[8];
+ return search_ROM_routine(&_pin, 0xF0, ROM_address);
+}
+
+bool MAX31850::unassignedProbe(DigitalInOut *pin, char *ROM_address) {
+ return search_ROM_routine(pin, 0xF0, ROM_address);
+}
+
+bool MAX31850::search_ROM_routine(DigitalInOut *pin, char command, char *ROM_address) {
+ bool DS1820_done_flag = false;
+ int DS1820_last_discrepancy = 0;
+ char DS1820_search_ROM[8] = {0, 0, 0, 0, 0, 0, 0, 0};
+
+ int discrepancy_marker, ROM_bit_index;
+ bool return_value, Bit_A, Bit_B;
+ char byte_counter, bit_mask;
+
+ return_value=false;
+ while (!DS1820_done_flag) {
+ if (!onewire_reset(pin)) {
+ return false;
+ } else {
+ ROM_bit_index=1;
+ discrepancy_marker=0;
+ char command_shift = command;
+ for (int n=0; n<8; n++) { // Search ROM command
+ onewire_bit_out(pin, command_shift & 0x01);
+ command_shift = command_shift >> 1; // now the next bit is in the least sig bit position.
+ }
+ byte_counter = 0;
+ bit_mask = 0x01;
+ while (ROM_bit_index<=64) {
+ Bit_A = onewire_bit_in(pin);
+ Bit_B = onewire_bit_in(pin);
+ if (Bit_A & Bit_B) {
+ discrepancy_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_discrepancy ) {
+ DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] | bit_mask; // Set ROM bit to one
+ } else {
+ if ( ROM_bit_index > DS1820_last_discrepancy ) {
+ DS1820_search_ROM[byte_counter] = DS1820_search_ROM[byte_counter] & ~bit_mask; // Set ROM bit to zero
+ discrepancy_marker = ROM_bit_index;
+ } else {
+ if (( DS1820_search_ROM[byte_counter] & bit_mask) == 0x00 )
+ discrepancy_marker = ROM_bit_index;
+ }
+ }
+ }
+ onewire_bit_out (pin, 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_discrepancy = discrepancy_marker;
+ if (ROM_bit_index != 0xFF) {
+ int i = 1;
+ node *list_container;
+ while(1) {
+ list_container = probes.pop(i);
+ if (list_container == NULL) { //End of list, or empty list
+ if (ROM_checksum_error(DS1820_search_ROM)) { // Check the CRC
+ return false;
+ }
+ for(byte_counter=0;byte_counter<8;byte_counter++)
+ ROM_address[byte_counter] = DS1820_search_ROM[byte_counter];
+ return true;
+ } else { //Otherwise, check if ROM is already known
+ bool equal = true;
+ MAX31850
+ *pointer = (MAX31850
+ *) list_container->data;
+ char *ROM_compare = pointer->_ROM;
+
+ for(byte_counter=0;byte_counter<8;byte_counter++) {
+ if ( ROM_compare[byte_counter] != DS1820_search_ROM[byte_counter])
+ equal = false;
+ }
+ if (equal)
+ break;
+ else
+ i++;
+ }
+ }
+ }
+ }
+ if (DS1820_last_discrepancy == 0)
+ DS1820_done_flag = true;
+ }
+ return return_value;
+}
+
+void MAX31850::match_ROM() {
+// Used to select a specific device
+ int i;
+ onewire_reset(&this->_datapin);
+ onewire_byte_out( 0x55); //Match ROM command
+ for (i=0;i<8;i++) {
+ onewire_byte_out(_ROM[i]);
+ }
+}
+
+void MAX31850::skip_ROM() {
+ onewire_reset(&this->_datapin);
+ onewire_byte_out(0xCC); // Skip ROM command
+}
+
+bool MAX31850::ROM_checksum_error(char *_ROM_address) {
+ char _CRC=0x00;
+ int i;
+ for(i=0;i<7;i++) // Only going to shift the lower 7 bytes
+ _CRC = CRC_byte(_CRC, _ROM_address[i]);
+ // After 7 bytes CRC should equal the 8th byte (ROM CRC)
+ return (_CRC!=_ROM_address[7]); // will return true if there is a CRC checksum mis-match
+}
+
+bool MAX31850::scratchpad_checksum_error() {
+ char _CRC=0x00;
+ int i;
+ for(i=0;i<8;i++) // Only going to shift the lower 8 bytes
+ _CRC = CRC_byte(_CRC, scratchpad[i]);
+ // After 8 bytes CRC should equal the 9th byte (scratchpad CRC)
+ return (_CRC!=scratchpad[8]); // will return true if there is a CRC checksum mis-match
+}
+
+char MAX31850::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 MAX31850::readAll() {
+ // Convert temperature into scratchpad for all devices at once
+ int delay_time = 75; //default delay time
+
+ skip_ROM(); //Skip ROM command, will convert for all devices
+
+ onewire_byte_out( 0x44); //perform temperature conversion
+
+ wait_ms(delay_time);
+}
+
+void MAX31850::read_scratchpad() {
+ // This will copy the MAX31850's 9 bytes of scratchpad data
+ // into the objects scratchpad array. Functions that use
+ // scratchpad values will automaticaly call this procedure.
+ int i;
+ match_ROM(); // Select this device
+ onewire_byte_out( 0xBE); //Read Scratchpad command
+ for(i=0;i<9;i++) {
+ scratchpad[i] = onewire_byte_in();
+ }
+}
+
+
+float MAX31850::getTemp(int scale) {
+ float answer;
+ int reading;
+ read_scratchpad();
+ if (scratchpad_checksum_error()) {
+ //indicate we got a CRC error
+ answer = invalid_conversion;
+ pc.printf("CRC Error\r\n");
+ }
+ else {
+ reading = (scratchpad[1] << 8) + scratchpad[0]; //combine first two bytes of scratchpad
+ reading = reading >> 2; //shift right two to drop unused bits
+ if (reading & 0x2000) { //check MSB to determin sign
+ reading = 0-((reading ^ 0x3fff) + 1); //use 2's compliment to convert back to positive number and make it a signed int
+ }
+ answer = reading +0.0; //convert to floating point
+ answer = answer / 4.0; //shift decimal place over two places
+
+ //unit convertion
+ //checks for passed in value first and if there is none it sets the units baced on class units variable
+ switch(scale) {
+ case C:
+ break;
+ case K:
+ answer = answer + 273.15f;
+ break;
+ case F:
+ answer = answer * 1.8f + 32.0f;
+ break;
+ case R:
+ answer = answer * 1.8f + 491.67f;
+ break;
+ default:
+ switch(_units) {
+ case C:
+ break;
+ case K:
+ answer = answer + 273.15f;
+ break;
+ case F:
+ answer = answer * 1.8f + 32.0f;
+ break;
+ case R:
+ answer = answer * 1.8f + 491.67f;
+ break;
+ }
+ }
+ }
+ return answer;
+}
+
+// Contributed by John M. Larkin (jlarkin@whitworth.edu)
+unsigned long long MAX31850::getId() {
+// This will return the 64 bit address of the connected MAX31850
+ unsigned long long myName = 0;
+ for (int i = 0; i<8; i++) {
+ myName = (myName<<8) | _ROM[i];
+ }
+ return myName;
+}
+
+void MAX31850::setUnits(int units) {
+ _units = units;
+}
\ No newline at end of file
