General area when it fits no where else

Moderator: Mmiscool

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By vag1500
#81199 Hi,
I am trying to communicate with Max31865 adafruit pcb with no success. I checked all pins and connections and also for confirmation I run the max31865 library with sample sketch (Arduino ide) and working fine which means that connections, pcb failures have been excluded. The esp8622 is from olimex and I am using the HSD port as per instruction manual (pins 12,13,14,15). Same I used with Arduino. The esp basic version is 3.0 alpha 69. Please find the below code that I am trying to read from register 0x00 unsuccessfully.
delay 1000
received_data = spi.hex(“00”,1)
print received_data
delay 100
delay 100
received_data = spi.hex(“00”,1)
print received_data
I always receive FF or 00. I tried with different frequencies (50000,1000000) with no success. Could you please revert what I am doing wrong?
Moreover please find working code with arduino IDE
#include <SPI.h>

//Registers defined in Table 1 on page 12 of the data sheet
static byte Configuration = 0b10000000; //0x80H
static byte read_Configuration = 0b00000000; //0x00H
static byte Write_High_Fault_Threshold_MSB = 0b10000011; //0x83H
static byte Write_High_Fault_Threshold_LSB = 0b10000100; //0x84H
static byte Read_High_Fault_Threshold_MSB = 0b00000011; //0x03H
static byte Read_High_Fault_Threshold_LSB = 0b00000100; //0x04H
static byte Write_Low_Fault_Threshold_MSB = 0b10000101; //0x85H
static byte Write_Low_Fault_Threshold_LSB = 0b10000110; //0x86H
static byte Read_Low_Fault_Threshold_MSB = 0b00000101; //0x05H
static byte Read_Low_Fault_Threshold_LSB = 0b00000110; //0x06H
static byte Fault_Status = 0b00000111; //0x07H

//Callendar-Van Dusen equation is used for temperature linearization. Coeffeicant of equations are as follows:
//R(T) = R0(1 + aT + bT^2 + c(T - 100)T^3)
//Equation from : ... 15_136.pdf
static float a = 0.00390830;
static float b = -0.0000005775;
static float c = -0.00000000000418301;
float Reference_Resistor; //Reference Resistor installed on the board.
float RTD_Resistance; //RTD Resistance at 0 Degrees. Please refer to your RTD data sheet.

//local variables
double Temperature = 0; //Variable defined to read data from getTemp() and display on serial console.
byte Fault_Error = 0; //Variable to read Fault register and compute faults
byte value = 0; // defined a variable to display the contents on the serial output
const int slaveSelectPin = 15; //using Digital Pin 52 for Chip Select
//int DRDY = 50;

/* Write(byte, byte) function requires the register address and the data to be written to the register provided when called in the respective sequence.
Write function does require that slaveSelectPin is properly defined in the setup. Changing the variable name of slaveSelectPin would require a change in Write function "slaveSelectPin" name as well
void Write(byte w_addr, byte data)
{ digitalWrite(slaveSelectPin,LOW);

//Read function(byte ) accepts the register address to be read and returns the contents of the register to the loop function
byte Read(byte r_addr)
{ digitalWrite(slaveSelectPin,LOW);
SPI.transfer(r_addr); // read from configuration register
value = SPI.transfer(0xFF); // dummy write to provide SPI clock signals to read
return value;}

/* get_Temp() function checks if the fault bit (D0)of LSB RTD regiset is set. If so, the conversion is aborted. If the fault
bit is not set, the conversion is initiated. The Digital Code is then computed to a temperature value and printed on the serial console.

For linearization, Callendar-Van Dusen equation is used.
R(T) = R0(1 + aT + bT^2 + c(T - 100)T^3)
void get_Temp()
{ byte lsb_rtd = Read(0x02);
byte fault_test = lsb_rtd&0x01;
while(fault_test == 0)
//if(digitalRead(DRDY) == 0)
byte msb_rtd = Read(0x01);
float RTD = ((msb_rtd << 7)+((lsb_rtd & 0xFE) >> 1)); //Combining RTD_MSB and RTD_LSB to protray decimal value. Removing MSB and LSB during shifting/Anding
float R = (RTD*Reference_Resistor)/32768; //Conversion of ADC RTD code to resistance
float Temp = -RTD_Resistance*a + sqrt(RTD_Resistance*RTD_Resistance*a*a - 4*RTD_Resistance*b*(RTD_Resistance-R)); //Conversion of RTD resistance to Temperature
Temp = Temp/(2*RTD_Resistance*b);
Serial.print("Temperature measured from RTD is: "); Serial.println(Temp, 4 ); //Printing Temperature on console
lsb_rtd = Read(0x02);
fault_test = lsb_rtd&0x01;

Serial.println("Error was detected. The RTD resistance measured is not within the range specified in the Threshold Registers.");

//Fault(byte) function requires the contents of the fault bit to be provided. It checks for the bits that are set and provides the faulty bit information on the serial console.
void Fault(byte fault)
{Serial.println(fault, BIN);
byte temp = 0; //temporary variable created: Purpose is to find out which error bit is set in the fault register
temp = fault & 0x80; //Logic Anding fault register contents with 0b10000000 to detect for D7 error bit
if(temp>0) {Serial.println("Bit D7 is Set. It's Possible your RTD device is disconnected from RTD+ or RTD-. Please verify your connection and High Fault Threshold Value");}
temp = fault & 0x40;
if(temp>0) {Serial.println("Bit D6 is Set. It's Possible your RTD+ and RTD- is shorted. Please verify your connection and your Low Fault Threshold Value."); }
temp = fault & 0x20;
if(temp>0){Serial.println("Bit D5 is Set. Vref- is greater than 0.85 * Vbias");}
temp = fault & 0x10;
if(temp>0){Serial.println("Bit D4 is Set. Please refer to data sheet for more information");}
temp = fault &0x08;
if(temp>0){Serial.println("Bit D3 is Set. Please refer to data sheet for more information");}
temp = fault &0x04;
if(temp>0){Serial.println("Bit D2 is Set. Please refer to data sheet for more information");}

void setup() {
Serial.begin(9600); // Serial Communication Baud Rate
pinMode (slaveSelectPin, OUTPUT); // Defining CS terminal as Output
// pinMode (DRDY, INPUT); // DRDY termianl as Input
SPI.setClockDivider(128); // Setting SPI clock to 625 MHz. Please note it is important to initialize SPI bus prior to making any changes.
Serial.println("This is sample code of MAX31865 - RTD to Digital Converter:");
Write(Configuration, 0b10000000); //Enabling Vbias of max31865
value = Read(read_Configuration); //Reading contents of Configuration register to verify communication with max31865 is done properly
if (value == 128)
{ Write(Write_High_Fault_Threshold_MSB, 0xFF); //Writing High Fault Threshold MSB
Write(Write_High_Fault_Threshold_LSB, 0xFF); //Writing High Fault Threshold LSB
Write(Write_Low_Fault_Threshold_MSB, 0x00); //Writing Low Fault Threshold MSB
Write(Write_Low_Fault_Threshold_MSB, 0x00); //Writing Low Fault Threshold LSB
Reference_Resistor = 430; //Reference Resistor installed on EVM
RTD_Resistance = 100; //RTD Resistance at 0 Degrees
Serial.println("Communication successful with max31865");}
{ Serial.println(" Unable to communicate with the device. Please check your connections and try again");}

void loop()
{ //Prior to getting started with RTD to Digital Conversion, Users can do a preliminary test to detect if their is a fault in RTD connection with max31865
Fault_Error = Read(Fault_Status);

//If their is no fault detected, the get_Temp() is called and it initiates the conversion. The results are displayed on the serial console
if(Fault_Error == 0)
{ Write(Configuration, 0b11000000);
get_Temp(); //Calling get_Temp() to read RTD registers and convert to Temperature reading
//If a fault is detected, Fault register is called and list of faults are displayed in the Serial console. Users are expected to troubleshoot the faults prior to proceeding
Serial.println("Fault Detected. Please refer to fault bits below: ");
Serial.println(" ");
Write(Configuration, 0b10000010);delay(700); //Fault register isn't cleared automatically. Users are expected to clear it after every fault.
Write(Configuration, 0b11000000);delay(700); } //Setting the device in autoconfiguration again.
User avatar
By vag1500
#81458 Hi all,

I have managed to add the Max31865 as new library in source file. You need the 3 files inside the rar to add them. Moreover i used Visual studio 2017 with vMicro which has better IDE interface than Arduino. I tried first to add it as library but the results was mess. Esp8266 crashes because i think pass inside a lot of functions. In addition i found the #define(name) and the #if defined name #endif very useful. You can build each time different code without proceed with many changes.
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User avatar
By vag1500
#81459 Sorry i forgot to inform you how you can work with this.
pt.setup(pttype,cspin,pinwire) where pttype 1=PT100 2=PT1000 cspin for example 15 and pinwire where
1=3 wires and 2= 2or 4 wires.

after setup you can call pt.temp() and read the temperature from PT sensor. Finally there is one more function in library pt.fault where it is empty string "" if there is no error in other case the string has the fault description.
example code:
pt.setup(1,15,2) 'set pt100 pin 15 as cs and 2 or 4 wire connection
let curr = "Calc" 'create variable with "Calc" text
curr = pt.temp() 'read the temp
message = pt.fault() 'read if there any fault