Revision 0:fae5dcebf741, committed 2018-09-28

Comitter:

JeroenAero

Date:

Fri Sep 28 20:11:03 2018 +0000

Commit message:

PT100 RTD TEMPERATURE SENSOR AMPLIFIER - MAX31865 ; Library with sample program.

Changed in this revision

diff -r 000000000000 -r fae5dcebf741 max31865.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/max31865.cpp	Fri Sep 28 20:11:03 2018 +0000
@@ -0,0 +1,147 @@
+#include "max31865.h"
+#include "mbed.h"
+
+max31865::max31865(PinName MOSI, PinName MISO, PinName SCLK, PinName CS) : spi(MOSI, MISO, SCLK), cs(CS) // mosi, miso, sclk
+{
+    //constructor
+    cs = 1; //deselect chip
+    spi.format(8,1); //set mode 1 and 8 bit
+    spi.frequency(500000); //set frequency to 0.5mhz
+    
+    
+}
+
+int max31865::ReadRTD()
+{
+    ClearFault();
+    EnableBias(true);
+    
+    int t = ReadRegistor8(MAX31856_CONFIG_REG);
+    t |= MAX31856_CONFIG_1SHOT;
+    WriteRegistor(MAX31856_CONFIG_REG, t);
+    
+    int RTD = ReadRegistor16(MAX31856_RTDMSB_REG);
+    
+    // remove fault
+    RTD >>= 1;
+     
+    return RTD;    
+}
+
+void max31865::Begin(max31865_numwires_t wires)
+{
+    cs = 1;
+    SetWires(wires);
+    EnableBias(false);
+    AutoConvert(false);
+    ClearFault();   
+}
+
+int max31865::ReadFault()
+{
+    return ReadRegistor8(MAX31856_FAULTSTAT_REG);
+}
+
+void max31865::ClearFault()
+{
+    int t = ReadRegistor8(MAX31856_CONFIG_REG);
+    t &= ~0x2C;
+    t |= MAX31856_CONFIG_FAULTSTAT;
+    WriteRegistor(MAX31856_CONFIG_REG, t);
+}
+
+void max31865::EnableBias(bool b)
+{
+    int t = ReadRegistor8(MAX31856_CONFIG_REG);
+    if (b)
+    {
+        t |= MAX31856_CONFIG_BIAS;       // enable bias
+    }
+    else
+    {
+        t &= ~MAX31856_CONFIG_BIAS;       // disable bias
+    }
+    WriteRegistor(MAX31856_CONFIG_REG, t);
+}
+
+void max31865::AutoConvert(bool b)
+{
+    int t = ReadRegistor8(MAX31856_CONFIG_REG);
+    if (b)
+    {
+        t |= MAX31856_CONFIG_MODEAUTO;       // enable autoconvert
+    }
+    else
+    {
+        t &= ~MAX31856_CONFIG_MODEAUTO;       // disable autoconvert
+    }
+    WriteRegistor(MAX31856_CONFIG_REG, t);   
+}
+
+void max31865::SetWires(max31865_numwires_t wires )
+{
+    int t = ReadRegistor8(MAX31856_CONFIG_REG);
+    
+    if (wires == MAX31865_3WIRE) 
+    {
+        t |= MAX31856_CONFIG_3WIRE;
+    } 
+    else 
+    {
+        // 2 or 4 wire
+        t &= ~MAX31856_CONFIG_3WIRE;
+    }
+    WriteRegistor(MAX31856_CONFIG_REG, t);
+}
+
+
+int max31865::ReadRegistor8(int address)
+{
+    int ret = 0;
+    ReadRegistorN(address, &ret, 1);
+    return ret;      
+}
+
+int max31865::ReadRegistor16(int address)
+{
+    int buffer[2] = {0, 0};
+    ReadRegistorN(address, buffer, 2);
+
+    int ret = buffer[0];
+    ret <<= 8;
+    ret |=  buffer[1];
+  
+    return ret;  
+}
+
+void max31865::ReadRegistorN(int address, int buffer[], int n)
+{
+    address &= 0x7F; // make sure top bit is not set 
+     
+    cs = 0;
+     
+    spiXfer(address);
+     
+    while(n--)
+    {
+        buffer[0] = spiXfer(0xFF);
+        buffer++;   
+    }
+    
+    cs = 1;
+}
+
+void max31865::WriteRegistor(int address, int data)
+{
+    
+    cs = 0; //select chip
+    spiXfer(address | 0x80);   // make sure top bit is set
+    spiXfer(data);
+    
+    cs = 1;
+}
+
+int max31865::spiXfer(int x)
+{
+    return spi.write(x);   
+}
\ No newline at end of file

diff -r 000000000000 -r fae5dcebf741 max31865.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/max31865.h	Fri Sep 28 20:11:03 2018 +0000
@@ -0,0 +1,67 @@
+#ifndef MBED_MAX31865_H
+#define MBED_MAX31865_H
+
+#include "mbed.h"
+
+#define MAX31856_CONFIG_REG            0x00
+#define MAX31856_CONFIG_BIAS           0x80
+#define MAX31856_CONFIG_MODEAUTO       0x40
+#define MAX31856_CONFIG_MODEOFF        0x00
+#define MAX31856_CONFIG_1SHOT          0x20
+#define MAX31856_CONFIG_3WIRE          0x10
+#define MAX31856_CONFIG_24WIRE         0x00
+#define MAX31856_CONFIG_FAULTSTAT      0x02
+#define MAX31856_CONFIG_FILT50HZ       0x01
+#define MAX31856_CONFIG_FILT60HZ       0x00
+
+#define MAX31856_RTDMSB_REG           0x01
+#define MAX31856_RTDLSB_REG           0x02
+#define MAX31856_HFAULTMSB_REG        0x03
+#define MAX31856_HFAULTLSB_REG        0x04
+#define MAX31856_LFAULTMSB_REG        0x05
+#define MAX31856_LFAULTLSB_REG        0x06
+#define MAX31856_FAULTSTAT_REG        0x07
+
+
+#define MAX31865_FAULT_HIGHTHRESH     0x80
+#define MAX31865_FAULT_LOWTHRESH      0x40
+#define MAX31865_FAULT_REFINLOW       0x20
+#define MAX31865_FAULT_REFINHIGH      0x10
+#define MAX31865_FAULT_RTDINLOW       0x08
+#define MAX31865_FAULT_OVUV           0x04
+
+typedef enum max31865_numwires { 
+  MAX31865_2WIRE = 0,
+  MAX31865_3WIRE = 1,
+  MAX31865_4WIRE = 0
+} max31865_numwires_t;
+
+class max31865 {
+    public:
+    
+    max31865(PinName MOSI, PinName MISO, PinName SCLK, PinName CS);
+    
+    void Begin(max31865_numwires_t x = MAX31865_2WIRE);
+    int ReadFault();
+    void ClearFault();
+    int ReadRTD();
+    
+    void SetWires(max31865_numwires_t wires);
+    void AutoConvert(bool b);
+    void EnableBias(bool b);
+    
+    private:
+    SPI spi;
+    DigitalOut cs;
+    
+    void ReadRegistorN(int address, int buffer[], int n);
+    
+    int ReadRegistor8(int address);
+    int ReadRegistor16(int address);
+    
+    void WriteRegistor(int address, int reg);
+    int spiXfer(int address);
+};
+
+
+#endif
\ No newline at end of file