diff --git a/Makefile b/Makefile
--- a/Makefile
+++ b/Makefile
@@ -10,7 +10,7 @@
 
 
 # SOURCES: list of sources in the user application
-SOURCES = main.c usbd_conf.c usbd_cdc_if.c usb_device.c usbd_desc.c stm32f0xx_hal_msp.c stm32f0xx_it.c system_stm32f0xx.c gpio.c spi.c ssd1306.c stringhelpers.c display.c bootlib.c storage.c flash.c
+SOURCES = main.c usbd_conf.c usbd_cdc_if.c usb_device.c usbd_desc.c stm32f0xx_hal_msp.c stm32f0xx_it.c system_stm32f0xx.c gpio.c spi.c ssd1306.c stringhelpers.c display.c bootlib.c storage.c flash.c max31855.c
 
 # TARGET: name of the user application
 TARGET = main
diff --git a/config.h b/config.h
--- a/config.h
+++ b/config.h
@@ -1,12 +1,24 @@
 #ifndef CONFIG_H
 #define CONFIG_H
 
+// Temperature sensor type
+#define MAX31855_TC_SENSOR
+//#define MAX31865_RTD_SENSOR
+
+
+// Virtual serial port transmit rate
 #define VCP_TX_FREQ 1000
+
+// Solid-state relay maximum on-time
 #define SSR_PERIOD 200
+
+// Interval of PID calculations
 #define PID_PERIOD 120
 
+
+
+// Pin settings
 #define LED_POWER GPIOF,GPIO_PIN_0
-
 #define MAX_CS GPIOA,GPIO_PIN_15
 
 #define SW_BTN  GPIOB, GPIO_PIN_4
diff --git a/main.c b/main.c
--- a/main.c
+++ b/main.c
@@ -3,6 +3,7 @@
 #include "config.h"
 #include "states.h"
 #include "ssd1306.h"
+#include "max31855.h"
 #include "gpio.h"
 #include "spi.h"
 #include "flash.h"
@@ -147,94 +148,6 @@ void SystemClock_Config(void)
 
 }
 
-
-// Grab temperature reading from MAX31855
-void update_temp() {
-
-    // Assert CS
-    HAL_GPIO_WritePin(MAX_CS, 0);
-
-    uint8_t rxdatah[1] = {0x00};
-    uint8_t rxdatal[1] = {0x00};
-
-    HAL_SPI_Receive(&hspi1, rxdatah, 1, 100);
-    HAL_SPI_Receive(&hspi1, rxdatal, 1, 100);
-
-    // Release CS
-    HAL_GPIO_WritePin(MAX_CS, 1);
-
-    // Assemble data array into one var
-    uint16_t temp_pre = rxdatal[0] | (rxdatah[0]<<8);
-/*
-    if(temp_pre & 0b010) {
-        ssd1306_clearscreen();
-        HAL_Delay(400); // FIXME: remove?
-        status.tc_errno = 4;
-        status.state = STATE_TC_ERROR;
-        status.temp = 0;
-        status.temp_frac = 0;
-    } */
-    if(temp_pre & 0b001 && !set.ignore_tc_error) {
-        status.tc_errno = 1;
-        HAL_Delay(400); // FIXME: remove?
-        status.state_resume = status.state;
-        status.state = STATE_TC_ERROR;
-        status.temp = 0;
-        status.temp_frac = 0;
-    }/*
-    else if(temp_pre & 0b100 && !set.ignore_tc_error) {
-        status.tc_errno = 8;
-        HAL_Delay(400); // FIXME: remove?
-        status.state_resume = status.state;
-        status.state = STATE_TC_ERROR;
-        status.temp = 0;
-        status.temp_frac = 0;
-    }*/
-    else 
-    {
-        //if(status.state == STATE_TC_ERROR)
-        //{
-        //    status.state = status.state_resume;
-        //    ssd1306_clearscreen();
-        //}
-
-        uint8_t sign = status.temp >> 15;// top bit is sign
-
-        temp_pre = temp_pre >> 2; // Drop 2 lowest bits
-        status.temp_frac = temp_pre & 0b11; // get fractional part
-        status.temp_frac *= 25; // each bit is .25 a degree, up to fixed point
-        temp_pre = temp_pre >> 2; // Drop 2 fractional bits 
-
-        int8_t signint;
-
-        if(sign) {
-            signint = -1;
-        }
-        else {
-            signint = 1;
-        }
-
-        // Convert to Fahrenheit
-        if(set.temp_units == TEMP_UNITS_FAHRENHEIT)
-        {
-            status.temp = signint * ((temp_pre*100) + status.temp_frac);
-            status.temp = status.temp * 1.8;
-            status.temp += 3200;
-            status.temp_frac = status.temp % 100;
-            status.temp /= 100;
-            status.temp += set.temp_offset;
-        }
-
-        // Use Celsius values
-        else
-        {
-            status.temp = temp_pre * signint;
-            status.temp += set.temp_offset;
-        }
-    }
-}
-
-
 // PID implementation
 // TODO: Make struct that has the last_temp and i_state in it, pass by ref. Make struct that has other input values maybe.
 int16_t last_pid_temp = 0;
@@ -308,7 +221,13 @@ void process()
 
     if((ticks - last_pid > PID_PERIOD))
     {
-        update_temp(); // Read MAX31855
+        #ifdef MAX31855_TC_SENSOR
+        max31855_readtemp(&hspi1, &set, &status); // Read MAX31855
+        #endif
+
+        #ifdef MAX31865_RTD_SENSOR
+        max31865_readtemp(&set, &status);
+        #endif
 
     HAL_GPIO_TogglePin(LED_POWER);
 
diff --git a/max31855.c b/max31855.c
new file mode 100644
--- /dev/null
+++ b/max31855.c
@@ -0,0 +1,94 @@
+#include "stm32f0xx_hal.h"
+
+#include "config.h"
+#include "stringhelpers.h"
+#include "states.h"
+#include "gpio.h"
+
+// Grab temperature reading from MAX31855
+void max31855_readtemp(SPI_HandleTypeDef* hspi1, therm_settings_t* set, therm_status_t* status)
+{
+    // Assert CS
+    HAL_GPIO_WritePin(MAX_CS, 0);
+
+    uint8_t rxdatah[1] = {0x00};
+    uint8_t rxdatal[1] = {0x00};
+
+    HAL_SPI_Receive(hspi1, rxdatah, 1, 100);
+    HAL_SPI_Receive(hspi1, rxdatal, 1, 100);
+
+    // Release CS
+    HAL_GPIO_WritePin(MAX_CS, 1);
+
+    // Assemble data array into one var
+    uint16_t temp_pre = rxdatal[0] | (rxdatah[0]<<8);
+/*
+    if(temp_pre & 0b010) {
+        ssd1306_clearscreen();
+        HAL_Delay(400); // FIXME: remove?
+        status.tc_errno = 4;
+        status.state = STATE_TC_ERROR;
+        status.temp = 0;
+        status.temp_frac = 0;
+    } */
+    if(temp_pre & 0b001 && !set->ignore_tc_error) {
+        status->tc_errno = 1;
+        HAL_Delay(400); // FIXME: remove?
+        status->state_resume = status->state;
+        status->state = STATE_TC_ERROR;
+        status->temp = 0;
+        status->temp_frac = 0;
+    }/*
+    else if(temp_pre & 0b100 && !set.ignore_tc_error) {
+        status.tc_errno = 8;
+        HAL_Delay(400); // FIXME: remove?
+        status.state_resume = status.state;
+        status.state = STATE_TC_ERROR;
+        status.temp = 0;
+        status.temp_frac = 0;
+    }*/
+    else 
+    {
+        //if(status.state == STATE_TC_ERROR)
+        //{
+        //    status.state = status.state_resume;
+        //    ssd1306_clearscreen();
+        //}
+
+        uint8_t sign = status->temp >> 15;// top bit is sign
+
+        temp_pre = temp_pre >> 2; // Drop 2 lowest bits
+        status->temp_frac = temp_pre & 0b11; // get fractional part
+        status->temp_frac *= 25; // each bit is .25 a degree, up to fixed point
+        temp_pre = temp_pre >> 2; // Drop 2 fractional bits 
+
+        int8_t signint;
+
+        if(sign) {
+            signint = -1;
+        }
+        else {
+            signint = 1;
+        }
+
+        // Convert to Fahrenheit
+        if(set->temp_units == TEMP_UNITS_FAHRENHEIT)
+        {
+            status->temp = signint * ((temp_pre*100) + status->temp_frac);
+            status->temp = status->temp * 1.8;
+            status->temp += 3200;
+            status->temp_frac = status->temp % 100;
+            status->temp /= 100;
+            status->temp += set->temp_offset;
+        }
+
+        // Use Celsius values
+        else
+        {
+            status->temp = temp_pre * signint;
+            status->temp += set->temp_offset;
+        }
+    }
+}
+
+
diff --git a/max31855.h b/max31855.h
new file mode 100644
--- /dev/null
+++ b/max31855.h
@@ -0,0 +1,6 @@
+#ifndef MAX31855_H
+#define MAX31855_H
+
+void max31855_readtemp(SPI_HandleTypeDef* hspi1, therm_settings_t* set, therm_status_t* status);
+
+#endif