From bd40ae23dabef040e284f36cec777e20d6a0199d Mon Sep 17 00:00:00 2001
From: eneller <erikneller@gmx.de>
Date: Thu, 8 Jan 2026 02:32:39 +0100
Subject: [PATCH] Initial Commit

---
 README.md   |  6 ++++++
 src/pid.cpp | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 README.md
 create mode 100644 src/pid.cpp

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..29e284d
--- /dev/null
+++ b/README.md
@@ -0,0 +1,6 @@
+# Reflow Plate
+Custom Reflow Plate inspired by [UnexpectedMaker
+ReflowMaster](https://github.com/UnexpectedMaker/ReflowMaster)
+[Pro](https://reflowmasterpro.com)
+using [PID](https://en.wikipedia.org/wiki/Proportional%E2%80%93integral%E2%80%93derivative_controller)
+to control a simple grill.
diff --git a/src/pid.cpp b/src/pid.cpp
new file mode 100644
index 0000000..c45c4c2
--- /dev/null
+++ b/src/pid.cpp
@@ -0,0 +1,38 @@
+const float k_p = 1.0;
+const float k_i = 3.0;
+const float k_d = 0.2;
+const float tick_millis = 30'000;
+
+float target;
+float measured;
+float error;
+float error_last;
+float output;
+float i;
+float d;
+
+unsigned long time_last_millis;
+unsigned long time_cur_millis;
+unsigned long time_delta_millis;
+
+float pid(float error, float error_last, unsigned long delta){
+    float p = k_p * error;
+    float i = i + (k_i * delta * error);
+    float d = k_d * (error - error_last) / delta;
+    return p+i+d;
+}
+
+void setup(){
+    time_last_millis = millis();
+}
+
+void loop(){
+    time_cur_millis = millis();
+    time_delta_millis = time_cur_millis - time_last_millis;
+    if (time_delta_millis > tick_millis) {
+        time_last_millis = time_cur_millis;
+        error_last = error;
+        error = target - measured;
+        output = pid(error, error_last, time_delta_millis);
+    }
+}