mbv: add async app, sorta works

mbv/apps/async/uart.h

@@ -0,0 +1,35 @@
+#pragma once
+
+#include <cstdint>
+#include <span>
+#include <string_view>
+
+void InitUarts();
+
+// block until the provided buffer is full
+void UartReadBlocking(std::span<std::byte> data);
+inline uint8_t UartReadByteBlocking() {
+    std::byte byte;
+    UartReadBlocking(std::span{&byte, 1});
+    return static_cast<uint8_t>(byte);
+}
+
+// send and poll the uart until transmitted
+void UartWriteCrash(std::span<const std::byte> data);
+inline void UartWriteCrash(std::string_view s) {
+    return UartWriteCrash(std::as_bytes(std::span{s.data(), s.size()}));
+}
+
+// block until room is available in tx fifo, then send
+void UartWriteBlocking(std::span<const std::byte> data);
+inline void UartWriteBlocking(std::string_view s) {
+    return UartWriteBlocking(std::as_bytes(std::span{s.data(), s.size()}));
+}
+
+void HandleUartTxFromIsr(void*, unsigned int transmitted);
+void HandleUartRxFromIsr(void*, unsigned int);
+void HandleUartIsr();
+
+uint8_t UartStatus();
+
+void LogStuff();