Integrate f1ll (compiles, untested)

app/src/app.cpp

@@ -0,0 +1,15 @@
+#include <app.h>
+
+#include <main.h>
+
+#include <f1ll/console_handler.h>
+
+void app_main() {
+  f1ll::console_handler::init(USART1, DMA1, LL_DMA_CHANNEL_5, LL_DMA_CHANNEL_4);
+
+  while (true) {
+    f1ll::console_handler::instance().print("->> Hello <<-\r\n");
+    LL_GPIO_TogglePin(LED_GPIO_Port, LED_Pin);
+    LL_mDelay(500);
+  }
+}

app/src/irq_bridge.cpp

@@ -0,0 +1,11 @@
+#include <irq_bridge.h>
+
+#include <f1ll/console_handler.h>
+
+void dma1_channel4_irq_handler() {
+  f1ll::console_handler::instance().tx_dma_isr();
+}
+
+void dma1_channel5_irq_handler() {
+  f1ll::console_handler::instance().rx_dma_isr();
+}