diff --git a/.cargo/config.toml b/.cargo/config.toml
index 1d4a03d..691ccb6 100644
--- a/.cargo/config.toml
+++ b/.cargo/config.toml
@@ -1,6 +1,9 @@
 [build]
 target = "thumbv6m-none-eabi"
 
+[env]
+DEFMT_LOG = "trace"
+
 [target.thumbv6m-none-eabi]
 rustflags = [
     "-C",
@@ -8,11 +11,13 @@ rustflags = [
     "-C",
     "link-arg=-Tlink.x",
     "-C",
+    "link-arg=-Tdefmt.x",
+    "-C",
     "no-vectorize-loops",
 ]
 
-runner = "picotool load --update --verify --execute -t elf"
+#runner = "picotool load --update --verify --execute -t elf"
 
 # This runner will find a supported SWD debug probe and flash your RP2040 over
 # SWD:
-# runner = "probe-rs run --chip RP2040"
+runner = "probe-rs run --chip RP2040 --protocol swd --speed 2000"
diff --git a/Cargo.lock b/Cargo.lock
index 15bef12..fb32a32 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -74,6 +74,12 @@ version = "0.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2d7e60934ceec538daadb9d8432424ed043a904d8e0243f3c6446bce549a46ac"
 
+[[package]]
+name = "bitflags"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
 [[package]]
 name = "bitflags"
 version = "2.13.0"
@@ -189,6 +195,47 @@ version = "0.3.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "80a4af69c60438a1a82af89d362f4729fd38db7b73f305a237636fad31ceb2bf"
 
+[[package]]
+name = "defmt"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2953bfe4f93bbd20cc71198842756f77d161884c99ebbabc41d80231ded88d1"
+dependencies = [
+ "bitflags 1.3.2",
+ "defmt-macros",
+]
+
+[[package]]
+name = "defmt-macros"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bad9c72e7ca2137e0dc3813245a0d282fd6daad32fd800af018306a9169b5fe8"
+dependencies = [
+ "defmt-parser",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.118",
+]
+
+[[package]]
+name = "defmt-parser"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "10d60334b3b2e7c9d91ef8150abfb6fa4c1c39ebbcf4a81c2e346aad939fee3e"
+dependencies = [
+ "thiserror",
+]
+
+[[package]]
+name = "defmt-rtt"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "05144944c117db54127a8ac17a3c9a28d55e7047bfddb950bcd20b4a94c79b10"
+dependencies = [
+ "critical-section",
+ "defmt",
+]
+
 [[package]]
 name = "digest"
 version = "0.10.7"
@@ -608,6 +655,16 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a513e167849a384b7f9b746e517604398518590a9142f4846a32e3c2a4de7b11"
 
+[[package]]
+name = "panic-probe"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fd402d00b0fb94c5aee000029204a46884b1262e0c443f166d86d2c0747e1a1a"
+dependencies = [
+ "cortex-m",
+ "defmt",
+]
+
 [[package]]
 name = "parking_lot"
 version = "0.12.5"
@@ -661,10 +718,13 @@ name = "pico"
 version = "0.1.0"
 dependencies = [
  "cortex-m-rt",
+ "defmt",
+ "defmt-rtt",
  "embedded-graphics",
  "embedded-hal 1.0.0",
  "heapless 0.9.3",
  "panic-halt",
+ "panic-probe",
  "rp2040-boot2",
  "rp2040-hal",
  "ssd1306",
@@ -797,7 +857,7 @@ version = "0.11.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "679341d22c78c6c649893cbd6c3278dcbe9fc4faa62fea3a9296ae2b50c14625"
 dependencies = [
- "bitflags",
+ "bitflags 2.13.0",
  "memchr",
  "unicase",
 ]
@@ -823,7 +883,7 @@ version = "0.5.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ed2bf2547551a7053d6fdfafda3f938979645c44812fbfcda098faae3f1a362d"
 dependencies = [
- "bitflags",
+ "bitflags 2.13.0",
 ]
 
 [[package]]
@@ -1072,6 +1132,26 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "thiserror"
+version = "2.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4288b5bcbc7920c07a1149a35cf9590a2aa808e0bc1eafaade0b80947865fbc4"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "2.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ebc4ee7f67670e9b64d05fa4253e753e016c6c95ff35b89b7941d6b856dec1d5"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.118",
+]
+
 [[package]]
 name = "typenum"
 version = "1.20.1"
diff --git a/Cargo.toml b/Cargo.toml
index 6ce17ed..3484e12 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,10 +5,13 @@ edition = "2024"
 
 [dependencies]
 cortex-m-rt = "0.7.5"
+defmt = "1.1.1"
+defmt-rtt = "1.3.0"
 embedded-graphics = "0.8.2"
 embedded-hal = "1.0.0"
 heapless = "0.9.3"
 panic-halt = "1.0.0"
+panic-probe = { version = "1.0.0", features = ["print-defmt"] }
 rp2040-boot2 = "0.3.0"
 rp2040-hal = { version = "0.12.0", features = ["critical-section-impl"] }
 ssd1306 = "0.10.0"
diff --git a/LEARNINGS.md b/LEARNINGS.md
new file mode 100644
index 0000000..df5a462
--- /dev/null
+++ b/LEARNINGS.md
@@ -0,0 +1,267 @@
+# Raspberry Pi Pico Debugging mit Rust
+
+## ST-Link V2 funktioniert nicht mit dem RP2040
+
+### Problem
+
+Beim Verbinden über `probe-rs` erschien:
+
+```text
+JtagGetIdcodeError
+```
+
+Mit OpenOCD:
+
+```text
+Error: init mode failed (unable to connect to the target)
+```
+
+### Ursache
+
+Der verwendete günstige ST-Link-V2-Klon konnte zwar erkannt werden und sogar die Zielspannung messen, war aber nicht in der Lage, zuverlässig mit dem RP2040 über SWD zu kommunizieren.
+
+### Lösung
+
+Verwendung der offiziellen **Raspberry Pi Debug Probe** (CMSIS-DAP).
+
+---
+
+## Raspberry Pi Debug Probe
+
+Die Raspberry Pi Debug Probe wird von `probe-rs` und OpenOCD nativ unterstützt.
+
+Verkabelung:
+
+```
+Debug Probe      Pico
+
+SWCLK  --------> SWCLK
+SWDIO  --------> SWDIO
+GND    --------> GND
+```
+
+Der Pico kann weiterhin separat per USB versorgt werden.
+
+---
+
+## Firmware der Debug Probe aktualisieren
+
+`probe-rs` meldete:
+
+```text
+The firmware on the probe is outdated.
+The minimum supported firmware version is 2.2.0.
+```
+
+### Lösung
+
+Firmware der Debug Probe mittels UF2-Datei aktualisieren.
+
+Danach funktionierte `probe-rs` problemlos.
+
+---
+
+## OpenOCD testen
+
+Zum Testen der SWD-Verbindung:
+
+```bash
+openocd \
+    -f interface/cmsis-dap.cfg \
+    -f target/rp2040.cfg
+```
+
+Erfolgreiche Verbindung erkennt man an:
+
+```text
+SWD DPIDR 0x0bc12477
+```
+
+---
+
+## probe-rs als Cargo Runner
+
+In `.cargo/config.toml`:
+
+```toml
+[target.thumbv6m-none-eabi]
+runner = "probe-rs run --chip RP2040 --protocol swd"
+```
+
+Dadurch führt `cargo run` automatisch aus:
+
+- Build
+- Flash
+- Reset
+- Start
+- RTT/defmt-Monitoring
+
+---
+
+## cargo run beendet sich nicht
+
+### Beobachtung
+
+Nach dem Flashen blieb `cargo run` geöffnet.
+
+### Erklärung
+
+Das ist beabsichtigt.
+
+`probe-rs run` bleibt mit dem Mikrocontroller verbunden, damit:
+
+- RTT gelesen werden kann
+- `defmt`-Logs angezeigt werden
+- später Debugging möglich ist
+
+---
+
+## defmt einrichten
+
+Benötigte Crates:
+
+```toml
+defmt = "1"
+defmt-rtt = "1"
+panic-probe = { version = "...", features = ["print-defmt"] }
+```
+
+Initialisierung:
+
+```rust
+use defmt_rtt as _;
+use panic_probe as _;
+```
+
+Logs:
+
+```rust
+defmt::info!("Hello!");
+defmt::warn!("Voltage low");
+defmt::debug!("Counter = {}", counter);
+```
+
+---
+
+## duplicate lang item: panic_impl
+
+### Problem
+
+```text
+duplicate lang item: panic_impl
+```
+
+### Ursache
+
+Es waren zwei Panic-Handler eingebunden.
+
+Beispielsweise:
+
+```rust
+use panic_halt as _;
+```
+
+und zusätzlich
+
+```rust
+use panic_probe as _;
+```
+
+### Lösung
+
+Es darf nur **ein** Panic-Handler vorhanden sein.
+
+Für `defmt` sollte ausschließlich `panic-probe` verwendet werden.
+
+---
+
+## Failed to parse defmt data
+
+### Problem
+
+```text
+Failed to parse defmt data
+
+defmt version found, but no .defmt section
+```
+
+### Ursache
+
+Das Linkerscript `defmt.x` wurde nicht eingebunden.
+
+### Lösung
+
+`.cargo/config.toml` erweitern:
+
+```toml
+rustflags = [
+    "-C", "link-arg=-Tlink.x",
+    "-C", "link-arg=-Tdefmt.x",
+]
+```
+
+---
+
+## Keine defmt-Ausgaben sichtbar
+
+### Ursache
+
+`DEFMT_LOG` war nicht gesetzt.
+
+### Lösung
+
+In `.cargo/config.toml`:
+
+```toml
+[env]
+DEFMT_LOG = "info"
+```
+
+oder
+
+```toml
+DEFMT_LOG = "debug"
+```
+
+oder
+
+```toml
+DEFMT_LOG = "trace"
+```
+
+Danach wurden die Log-Ausgaben sofort angezeigt.
+
+---
+
+## Debugging-Geschwindigkeit
+
+Anfangs wurde mit
+
+```text
+--speed 100
+```
+
+gearbeitet.
+
+Das funktioniert zuverlässig, ist aber sehr langsam.
+
+Später kann die Geschwindigkeit auf mehrere MHz erhöht werden, z.B.
+
+```text
+--speed 4000
+```
+
+was Flash- und Debug-Zeiten deutlich reduziert.
+
+---
+
+## Erkenntnisse
+
+- SWD benötigt lediglich:
+  - SWCLK
+  - SWDIO
+  - GND
+- Der Pico kann gleichzeitig per USB versorgt werden.
+- `probe-rs run` ersetzt den manuellen Flash-Vorgang.
+- `defmt` ist der De-facto-Standard für Logging im Rust-Embedded-Ökosystem.
+- Die Raspberry Pi Debug Probe funktioniert mit dem RP2040 deutlich zuverlässiger als günstige ST-Link-V2-Klone.
\ No newline at end of file
diff --git a/src/boilerplate.rs b/src/boilerplate.rs
index c2f81e1..bd2d468 100644
--- a/src/boilerplate.rs
+++ b/src/boilerplate.rs
@@ -1,4 +1,6 @@
+use defmt_rtt as _;
 use panic_halt as _;
+// use panic_probe as _;
 use rp2040_hal::{
     Timer,
     clocks::ClocksManager,
diff --git a/src/main.rs b/src/main.rs
index e217e3f..0fb9c8a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -16,6 +16,8 @@ use crate::display::DisplayModule;
 
 #[rp2040_hal::entry]
 fn main() -> ! {
+    defmt::info!("Controller started.");
+
     let PicoParts {
         timer,
         pins,