diff --git a/src/thermostat.c b/src/thermostat.c
new file mode 100644
--- /dev/null
+++ b/src/thermostat.c
@@ -0,0 +1,62 @@
+//
+// Thermostat: Thermostatic controller
+//
+
+#include "thermostat.h"
+#include "flash.h"
+#include "gpio.h"
+
+// PID implementation
+
+float thermostat_process(void)
+{
+
+//            #ifdef MAX31865_RTD_SENSOR
+//            max31865_readtemp(spi_get(), &set, &status);
+//			#else
+//			max31855_readtemp(spi_get(), &set, &status); // Read MAX31855
+//			#endif
+
+			float ssr_output = 0.0;
+			uint8_t thermostat_plant_on = 0;
+
+			// TODO: Migrate this FxP conversion to the readtemp code or similar
+			float temp = runtime_status()->temp;
+
+
+			// EMZ FIXME: This could be way simpler
+			if(flash_getsettings()->val.plant_type == PLANT_HEATER && runtime_status()->setpoint * 10 < temp - flash_getsettings()->val.hysteresis * 10)
+				thermostat_plant_on = 1;
+			else if(flash_getsettings()->val.plant_type == PLANT_HEATER && runtime_status()->setpoint * 10 > temp + flash_getsettings()->val.hysteresis * 10)
+				thermostat_plant_on = 0;
+
+			if(flash_getsettings()->val.plant_type == PLANT_COOLER && runtime_status()->setpoint * 10 > temp + flash_getsettings()->val.hysteresis * 10)
+				thermostat_plant_on = 1;
+			else if(flash_getsettings()->val.plant_type == PLANT_COOLER && runtime_status()->setpoint * 10 < temp - flash_getsettings()->val.hysteresis * 10)
+				thermostat_plant_on = 0;
+
+			// EMZ: TODO: Refactor to output_enabled or something
+			if(runtime_status()->pid_enabled && thermostat_plant_on)
+			{
+				// EMZ TODO: functionalize this
+				// put ssr output on display
+				ssd1306_drawstring("      ", 0, 90); //fixme: this is bad, but I can't get the old digits to clear otherwise
+				char tempstr[6];
+				itoa(ssr_output, tempstr, 10);
+				ssd1306_drawstring(tempstr, 0, 90);
+
+
+
+//                HAL_GPIO_WritePin(SSR_PIN, 1);
+				HAL_GPIO_WritePin(LED, 1);
+			}
+			else
+			{
+//                HAL_GPIO_WritePin(SSR_PIN, 0);
+				HAL_GPIO_WritePin(LED, 0);
+			}
+
+			return ssr_output;
+}
+
+