diff --git a/stm-firmware/Makefile b/stm-firmware/Makefile
index 44161ac..fc35fde 100644
--- a/stm-firmware/Makefile
+++ b/stm-firmware/Makefile
@@ -53,6 +53,8 @@ CFILES += stack-check.c
 
 CFILES += fatfs/diskio.c fatfs/ff.c fatfs/ffsystem.c fatfs/ffunicode.c fatfs/shimatta_sdio_driver/shimatta_sdio.c
 
+CFILES += pid-controller.c oven-driver.c
+
 DEFINES += -DDEBUGBUILD
 
 ###################################################################################
diff --git a/stm-firmware/include/reflow-controller/oven-driver.h b/stm-firmware/include/reflow-controller/oven-driver.h
new file mode 100644
index 0000000..0ba0610
--- /dev/null
+++ b/stm-firmware/include/reflow-controller/oven-driver.h
@@ -0,0 +1,24 @@
+/* Reflow Oven Controller
+*
+* Copyright (C) 2020  Mario Hüttel <mario.huettel@gmx.net>
+*
+* This file is part of the Reflow Oven Controller Project.
+*
+* The reflow oven controller is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License version 2 as
+* published by the Free Software Foundation.
+*
+* The Reflow Oven Control Firmware is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with the reflow oven controller project.
+* If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __OVEN_DRIVER_H__
+#define __OVEN_DRIVER_H__
+
+#endif /* __OVEN_DRIVER_H__ */
diff --git a/stm-firmware/include/reflow-controller/pid-controller.h b/stm-firmware/include/reflow-controller/pid-controller.h
new file mode 100644
index 0000000..1e64741
--- /dev/null
+++ b/stm-firmware/include/reflow-controller/pid-controller.h
@@ -0,0 +1,44 @@
+/* Reflow Oven Controller
+*
+* Copyright (C) 2020  Mario Hüttel <mario.huettel@gmx.net>
+*
+* This file is part of the Reflow Oven Controller Project.
+*
+* The reflow oven controller is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License version 2 as
+* published by the Free Software Foundation.
+*
+* The Reflow Oven Control Firmware is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with the reflow oven controller project.
+* If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __PID_CONTROLLER_H__
+#define __PID_CONTROLLER_H__
+
+struct pid_controller {
+	float k_deriv;
+	float k_int;
+	float k_p;
+	float output_sat_max;
+	float output_sat_min;
+	float integral_max;
+	volatile float control_output;
+	volatile float last_in;
+	volatile float integral;
+};
+
+void pid_init(struct pid_controller *pid, float k_deriv, float k_int, float k_p, float output_sat_min, float output_sat_max, float integral_max);
+
+void pid_zero(struct pid_controller *pid);
+
+float pid_sample(struct pid_controller *pid, float deviation);
+
+float pid_get_control_output(const struct pid_controller *pid);
+
+#endif /* __PID_CONTROLLER_H__ */
diff --git a/stm-firmware/oven-driver.c b/stm-firmware/oven-driver.c
new file mode 100644
index 0000000..27a7564
--- /dev/null
+++ b/stm-firmware/oven-driver.c
@@ -0,0 +1,21 @@
+/* Reflow Oven Controller
+*
+* Copyright (C) 2020  Mario Hüttel <mario.huettel@gmx.net>
+*
+* This file is part of the Reflow Oven Controller Project.
+*
+* The reflow oven controller is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License version 2 as
+* published by the Free Software Foundation.
+*
+* The Reflow Oven Control Firmware is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with the reflow oven controller project.
+* If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <reflow-controller/oven-driver.h>
diff --git a/stm-firmware/pid-controller.c b/stm-firmware/pid-controller.c
new file mode 100644
index 0000000..ef97235
--- /dev/null
+++ b/stm-firmware/pid-controller.c
@@ -0,0 +1,90 @@
+/* Reflow Oven Controller
+*
+* Copyright (C) 2020  Mario Hüttel <mario.huettel@gmx.net>
+*
+* This file is part of the Reflow Oven Controller Project.
+*
+* The reflow oven controller is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License version 2 as
+* published by the Free Software Foundation.
+*
+* The Reflow Oven Control Firmware is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+* GNU General Public License for more details.
+*
+* You should have received a copy of the GNU General Public License
+* along with the reflow oven controller project.
+* If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <reflow-controller/pid-controller.h>
+
+void pid_init(struct pid_controller *pid, float k_deriv, float k_int, float k_p, float output_sat_min, float output_sat_max, float integral_max)
+{
+	if (!pid)
+		return;
+
+	pid->k_p = k_p;
+	pid->k_int = k_int;
+	pid->k_deriv = k_deriv;
+	pid->output_sat_max = output_sat_max;
+	pid->output_sat_min = output_sat_min;
+	pid->control_output = 0;
+	pid->integral_max = integral_max;
+}
+
+void pid_zero(struct pid_controller *pid)
+{
+	pid->control_output = 0.0f;
+	pid->last_in = 0.0f;
+	pid->integral = 0.0f;
+}
+
+static void calculate_integral(struct pid_controller *pid, float deviation)
+{
+	pid->integral += deviation * pid->k_int;
+
+	if (pid->integral > pid->integral_max) {
+		pid->integral = pid->integral_max;
+	} else if (pid->integral < -pid->integral_max) {
+		pid->integral = -pid->integral_max;
+	}
+}
+
+float pid_sample(struct pid_controller *pid, float deviation)
+{
+	float output;
+
+	if (!pid)
+		return 0.0;
+
+	output = deviation * pid->k_p;
+
+	if (!(deviation > 0.0f && pid->control_output > pid->output_sat_max - 0.5) &&
+	    !(deviation < 0.0f && pid->control_output < pid->output_sat_min + 0.5)) {
+		calculate_integral(pid, deviation);
+	}
+
+	output += pid->integral;
+	output -= (deviation - pid->last_in) * pid->k_deriv;
+
+	pid->last_in = deviation;
+
+	if (output > pid->output_sat_max)
+		output = pid->output_sat_max;
+	if (output < pid->output_sat_min)
+		output = pid->output_sat_min;
+
+	pid->control_output = output;
+
+	return output;
+}
+
+float pid_get_control_output(const struct pid_controller *pid)
+{
+	if (!pid)
+		return 0.0f;
+
+	return pid->control_output;
+}