VesiScan BASIC origin: Piezo + IMU firmware initial code

- nRF52840 + SoftDevice S140 BLE firmware
- Piezo ultrasound TX driver (2MHz, 8ch MUX)
- ICM42670P IMU 6-axis driver
- Echo AFE chain (ADA2200 + ADC121S051)
- BLE NUS command parser (mpa/mpc/mdc/mec/maa/msp)
- FDS flash config storage
- pc_firm parser and ADC driver included

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pc_firm/dr_lua/dr_lua.c

@@ -0,0 +1,105 @@
+/*
+ * dr_lua.c
+ *
+ * Author : Charles KWON
+ *
+ * This module provides a simple and reusable interface layer
+ * between C firmware code and embedded Lua scripts.
+ * It is designed to make calling Lua functions from C firmware
+ * straightforward and safe.
+ *
+ * Example:
+ *   Lua function: add3(x) = x + 3
+ *   C function   : dr_lua_add3(int num1)
+ */
+
+#include "lua.h"
+#include "lauxlib.h"
+#include "lualib.h"
+
+/* -------------------------------------------------
+ * External output function (UART / RTT, etc.)
+ * This function must be implemented by the project.
+ * ------------------------------------------------- */
+extern void board_print(const char *s);
+
+/* -------------------------------------------------
+ * Global Lua state
+ * ------------------------------------------------- */
+static lua_State *g_L = NULL;
+
+/* -------------------------------------------------
+ * Initialize Lua VM
+ * ------------------------------------------------- */
+void dr_lua_init(void)
+{
+    g_L = luaL_newstate();
+
+    /* Load base library only */
+    luaL_requiref(g_L, "_G", luaopen_base, 1);
+    lua_pop(g_L, 1);
+}
+
+/* -------------------------------------------------
+ * Load Lua script
+ * Defines:
+ *   function add3(x)
+ *       return x + 3
+ *   end
+ * ------------------------------------------------- */
+void dr_lua_load_script(void)
+{
+    const char *lua_code =
+        "function add3(x)\n"
+        "    return x + 3\n"
+        "end";
+
+    if (luaL_dostring(g_L, lua_code) != LUA_OK) {
+        const char *err = lua_tostring(g_L, -1);
+        board_print(err);
+        lua_pop(g_L, 1);
+    }
+}
+
+/* -------------------------------------------------
+ * Core interface function
+ * Calls Lua function add3 from C firmware
+ *
+ * @param num1  Input integer value
+ * @return      Result of (num1 + 3)
+ *              -1 if Lua function is not found
+ *              -2 if Lua call fails
+ * ------------------------------------------------- */
+int dr_lua_add3(int num1)
+{
+    int result = 0;
+
+    /* 1. Get Lua function: add3 */
+    lua_getglobal(g_L, "add3");
+
+    if (!lua_isfunction(g_L, -1)) {
+        lua_pop(g_L, 1);
+        return -1;   /* Function not found */
+    }
+
+    /* 2. Push argument */
+    lua_pushinteger(g_L, num1);
+
+    /* 3. Call Lua function (1 argument, 1 return value) */
+    if (lua_pcall(g_L, 1, 1, 0) != LUA_OK) {
+        const char *err = lua_tostring(g_L, -1);
+        board_print(err);
+        lua_pop(g_L, 1);
+        return -2;   /* Call failed */
+    }
+
+    /* 4. Read return value */
+    if (lua_isinteger(g_L, -1)) {
+        result = (int)lua_tointeger(g_L, -1);
+    }
+
+    /* 5. Clean up Lua stack */
+    lua_pop(g_L, 1);
+
+    return result;   /* num1 + 3 */
+}