From 9edf5a953c98f16061c5a4c11b4cf408bf727b03 Mon Sep 17 00:00:00 2001
From: GlassOnTin <GlassOnTin@users.noreply.github.com>
Date: Tue, 31 Mar 2026 14:00:56 +0100
Subject: [PATCH] Add SD card file listing via debug command F

Implements gui_list_files_fn callback to list SD card contents
as JSON via the serial debug protocol. Replaces the stub that
returned "use_log_command".
---
 Gui.h              | 12 +++++++-----
 RNode_Firmware.ino | 22 ++++++++++++++++++++++
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/Gui.h b/Gui.h
index 4f9215e..dc1a265 100644
--- a/Gui.h
+++ b/Gui.h
@@ -158,6 +158,9 @@ extern volatile uint32_t imu_step_count;
 // Sensor logger toggle — set by .ino after IMULogger.h is included
 typedef bool (*gui_log_toggle_fn_t)();
 static gui_log_toggle_fn_t gui_log_toggle_fn = NULL;
+// SD file listing — set by .ino after SD is available
+typedef void (*gui_list_files_fn_t)();
+static gui_list_files_fn_t gui_list_files_fn = NULL;
 static bool gui_imu_logging = false;
 // Forward declarations for IMULogger.h variables (defined later in compilation)
 extern bool imu_logging;
@@ -1322,13 +1325,12 @@ static void gui_cmd_execute() {
             break;
         }
 
-        case 'F': {  // List files on SD card (handled via function pointer)
+        case 'F': {  // List files on SD card
             Serial.write(hdr, 4);
-            if (gui_log_toggle_fn) {
-                // Reuse the SD infrastructure from IMU logger
-                Serial.println("{\"error\":\"use_log_command\"}");
+            if (gui_list_files_fn) {
+                gui_list_files_fn();
             } else {
-                Serial.println("{\"error\":\"not_available\"}");
+                Serial.println("{\"error\":\"no_sd\"}");
             }
             Serial.flush();
             break;
diff --git a/RNode_Firmware.ino b/RNode_Firmware.ino
index 362e446..b38caa7 100644
--- a/RNode_Firmware.ino
+++ b/RNode_Firmware.ino
@@ -2236,6 +2236,28 @@ void loop() {
             return false;
           }
         };
+        gui_list_files_fn = []() {
+          if (shared_spi_mutex) xSemaphoreTake(shared_spi_mutex, portMAX_DELAY);
+          SPI.begin(SD_CLK, SD_MISO, SD_MOSI, SD_CS);
+          if (SD.begin(SD_CS, SPI, 4000000, "/sd", 5)) {
+            Serial.print("{\"files\":[");
+            File root = SD.open("/");
+            bool first = true;
+            File f;
+            while ((f = root.openNextFile())) {
+              if (!first) Serial.print(",");
+              Serial.printf("{\"name\":\"%s\",\"size\":%lu}", f.name(), (unsigned long)f.size());
+              first = false;
+              f.close();
+            }
+            root.close();
+            SD.end();
+            Serial.println("]}");
+          } else {
+            Serial.println("{\"error\":\"sd_init_failed\"}");
+          }
+          if (shared_spi_mutex) xSemaphoreGive(shared_spi_mutex);
+        };
         #endif
 
         // Enable step counter (low power, always-on)