Added PCBs

firmware/sd_test/sd_test.ino

@@ -0,0 +1,36 @@
+#include <SPI.h>
+#include <SD.h>
+
+#define CS_PIN 5
+
+void setup() {
+  Serial.begin(115200);
+  
+  // Initialize SD card
+  if (!SD.begin(CS_PIN)) {
+    Serial.println("Card Mount Failed");
+    return;
+  }
+  Serial.println("Card Initialized");
+
+  // Create and open file
+  File file = SD.open("/HelloWorld.txt", FILE_WRITE);
+  
+  // Check if the file opened successfully
+  if (!file) {
+    Serial.println("Failed to open file for writing");
+    return;
+  }
+  
+  // Write to file
+  file.println("Hello World!");
+  
+  // Close the file
+  file.close();
+  
+  Serial.println("File written successfully");
+}
+
+void loop() {
+  // Nothing to do here
+}