add spi e-ink display

commands/echo.cpp

@@ -0,0 +1,22 @@
+#include <stdio.h>
+#include <ctype.h>
+#include <cstring>
+
+#include "echo.h"
+
+// Helper function to handle the echoing and resetting of the buffer
+void echo_and_reset(char* buffer, int* index_ptr) {
+    if (*index_ptr > 0) {
+        buffer[*index_ptr] = '\0';
+        // Print to USB serial (ALL CAPS)
+        printf("\nEchoed (ALL CAPS): ");
+        for (int i = 0; buffer[i] != '\0'; i++) {
+            char ch = toupper(buffer[i]);
+            printf("%c", ch);
+        }
+        printf("\n");
+    }
+
+    *index_ptr = 0;
+    printf("> ");
+}

commands/echo.h

@@ -0,0 +1,14 @@
+#ifndef COMMANDS_ECHO_H
+#define COMMANDS_ECHO_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void echo_and_reset(char* buffer, int* index_ptr);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // COMMANDS_ECHO_H