diff --git a/src/main.rs b/src/main.rs
index 67e181c..9717ebc 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -76,6 +76,7 @@ esp_bootloader_esp_idf::esp_app_desc!();
 #[cfg(feature = "_gnss")]
 static GNSS_UPDATE: Mutex<RefCell<Option<applogic::GnssFix>>> = Mutex::new(RefCell::new(None));
 static WIFI_RX_QUEUE: Mutex<RefCell<Option<ArrayQueue<Vec<u8>>>>> = Mutex::new(RefCell::new(None));
+static mut USER_LED: Option<esp_hal::gpio::Output<'static>> = None;
 #[cfg(feature = "_uart")]
 static UART_RX_BUF: Mutex<RefCell<Option<Vec<u8>>>> = Mutex::new(RefCell::new(None));
 #[cfg(feature = "_uart")]
@@ -176,6 +177,13 @@ async fn main(spawner: Spawner) -> ! {
         error!("Failed to set WiFi TX power: {err}");
     }
 
+    unsafe {
+        USER_LED = Some(esp_hal::gpio::Output::new(
+            peripherals.GPIO27,
+            esp_hal::gpio::Level::Low,
+            esp_hal::gpio::OutputConfig::default(),
+        ));
+    }
     critical_section::with(|cs| {
         WIFI_RX_QUEUE.borrow(cs).replace(Some(ArrayQueue::new(2)));
     });
@@ -546,6 +554,12 @@ fn handle_frame(frame: esp_radio::wifi::sniffer::PromiscuousPkt<'_>) {
     }
 
     // info!("Received frame with {} bytes", frame.len);
+    unsafe {
+        #[allow(static_mut_refs)]
+        if let Some(ref mut led) = USER_LED.as_mut() {
+            led.toggle();
+        }
+    }
 
     // parse GN headers
     match c_its_parser::pcap::remove_wlan_headers(frame.data)
@@ -560,6 +574,7 @@ fn handle_frame(frame: esp_radio::wifi::sniffer::PromiscuousPkt<'_>) {
         Ok(packet) => {
             // drop hopped (for now)
             if packet.decoded.is_hopped() {
+                esp_println::print!("."); // TODO: debug only!
                 return;
             }
 
@@ -568,9 +583,15 @@ fn handle_frame(frame: esp_radio::wifi::sniffer::PromiscuousPkt<'_>) {
                 // drop all unsupported message IDs and rate-limit SPATEMs
                 if match message_id {
                     #[cfg(feature = "denm")]
-                    c_its_parser::standards::extensions::ItsMessageId::Denm => false,
+                    c_its_parser::standards::extensions::ItsMessageId::Denm => {
+                        esp_println::print!("D"); // TODO: debug only!
+                        false
+                    }
                     #[cfg(feature = "cam")]
-                    c_its_parser::standards::extensions::ItsMessageId::Cam => false,
+                    c_its_parser::standards::extensions::ItsMessageId::Cam => {
+                        esp_println::print!("C"); // TODO: debug only!
+                        false
+                    }
                     #[cfg(feature = "spat")]
                     c_its_parser::standards::extensions::ItsMessageId::Spatem => {
                         // reduce SPAT rate per station ID
@@ -586,7 +607,10 @@ fn handle_frame(frame: esp_radio::wifi::sniffer::PromiscuousPkt<'_>) {
                                 i.msg_count = i.msg_count.wrapping_add(1);
 
                                 if (i.msg_count % SPAT_RATE_LIMIT) > 0 {
+                                    esp_println::print!("s"); // TODO: debug only!
                                     drop_msg = true;
+                                } else {
+                                    esp_println::print!("S"); // TODO: debug only!
                                 }
                             });
                         }
@@ -594,8 +618,14 @@ fn handle_frame(frame: esp_radio::wifi::sniffer::PromiscuousPkt<'_>) {
                         drop_msg
                     }
                     #[cfg(feature = "spat")]
-                    c_its_parser::standards::extensions::ItsMessageId::Mapem => false,
-                    _ => true,
+                    c_its_parser::standards::extensions::ItsMessageId::Mapem => {
+                        esp_println::print!("M"); // TODO: debug only!
+                        false
+                    }
+                    _ => {
+                        esp_println::print!("?"); // TODO: debug only!
+                        true
+                    }
                 } {
                     return;
                 }