From ba0f775bb9bcb4397544d8c2a8a5820cf902ab0c Mon Sep 17 00:00:00 2001
From: Scott Penrose <scottp@dd.com.au>
Date: Tue, 7 Jul 2026 11:54:46 +1000
Subject: [PATCH] Passthrough version

---
 app/wii5_passthrough/wii5_passthrough.ino | 76 +++++++++++++++++++++++
 pio_main_passthrough.cpp                  | 21 +++++++
 platformio.ini                            | 11 ++++
 3 files changed, 108 insertions(+)
 create mode 100644 app/wii5_passthrough/wii5_passthrough.ino
 create mode 100644 pio_main_passthrough.cpp

diff --git a/app/wii5_passthrough/wii5_passthrough.ino b/app/wii5_passthrough/wii5_passthrough.ino
new file mode 100644
index 0000000..8baaa88
--- /dev/null
+++ b/app/wii5_passthrough/wii5_passthrough.ino
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright (c) 2012-2024 Scott Penrose <scottp@dd.com.au> and WII5 Buoy contributors
+//
+// This file is part of WII5 Buoy firmware.
+// See LICENSE for full terms.
+
+/**
+ * @file wii5_passthrough.ino
+ * @brief Minimal firmware: keeps the Maths CPU powered on and provides
+ *        bidirectional raw serial passthrough to the Iridium modem.
+ *
+ * The AVR becomes a transparent bridge between the USB console and the
+ * Iridium 9602/9603 modem (Serial3 @ 19200 baud). AT commands typed on
+ * the console go directly to the modem; modem responses are echoed back.
+ *
+ * Maths CPU (Raspberry Pi) is kept alive indefinitely via the hold timer
+ * and the MATHS_RETURNLINE hardware signal.
+ *
+ * Build (PlatformIO):
+ *   pio run -e wii5_passthrough
+ */
+
+#include <Arduino.h>
+#include <WII5.h>
+
+elapsedMillis wdtWait;
+elapsedMillis holdCheckWait;
+
+void setup() {
+  wii5Setup.beginSafe();
+  wii5Setup.setupConsole();
+
+  // Maths CPU — start and hold on indefinitely
+  wii5Maths.begin();
+  wii5Maths.start(WII5MATHSMODE_COMMS);
+  wii5Maths.setHold(MATHS_MAXHOLD);
+  wii5Maths.setReturnLine();
+
+  // Iridium modem — initialise, then power on with passthrough
+  wii5Iridium.begin();
+  wii5Iridium.setPassthrough(true);
+  wii5Iridium.powerOn(true);
+
+  wdtWait = 0;
+  holdCheckWait = 0;
+}
+
+void loop() {
+  // ---- external watchdog ----
+#ifdef WDT_RESET
+  if (wdtWait > 5100) {
+    digitalWrite(WDT_RESET, LOW);
+    wdtWait = 0;
+  } else if (wdtWait > 5000) {
+    digitalWrite(WDT_RESET, HIGH);
+  }
+#endif
+
+  // ---- Maths CPU keep-alive ----
+  wii5Maths.loop();
+  if (holdCheckWait > 30000) {
+    holdCheckWait = 0;
+    if (wii5Maths.remainingHold() < 600) {
+      wii5Maths.setHold(MATHS_MAXHOLD);
+    }
+    wii5Maths.setReturnLine();
+  }
+
+  // ---- Modem → Console (passthrough echo) ----
+  wii5Iridium.WII5SerialManager::loop();
+
+  // ---- Console → Modem (raw forwarding) ----
+  while (SerialConsole.available()) {
+    SerialComms.write(SerialConsole.read());
+  }
+}
diff --git a/pio_main_passthrough.cpp b/pio_main_passthrough.cpp
new file mode 100644
index 0000000..76fec75
--- /dev/null
+++ b/pio_main_passthrough.cpp
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright (c) 2012-2024 Scott Penrose <scottp@dd.com.au> and WII5 Buoy contributors
+//
+// This file is part of WII5 Buoy firmware.
+// See LICENSE for full terms.
+
+/**
+ * @file pio_main_passthrough.cpp
+ * @brief PlatformIO entry shim for the wii5_passthrough sketch.
+ *
+ * PlatformIO only auto-detects a sketch at the top level of its source
+ * directory.  This shim pulls wii5_passthrough.ino into the PlatformIO
+ * build (where setup() / loop() are defined).
+ *
+ * It is gated on PLATFORMIO so that the arduino-cli build never sees a
+ * second definition of setup() / loop().
+ */
+
+#if defined(PLATFORMIO)
+#include "app/wii5_passthrough/wii5_passthrough.ino"
+#endif
diff --git a/platformio.ini b/platformio.ini
index e2b39a8..dec39f0 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -36,6 +36,7 @@ monitor_speed = 230400
 ; The entry sketch (app/wii5_buoy/wii5_buoy.ino) is pulled in by pio_main.cpp.
 build_src_filter =
     +<*.cpp>
+    -<pio_main_passthrough.cpp>
 
 ; The project's own headers are included with angle brackets (<WII5.h>, ...),
 ; so the repo root must be on the include path. Software version/commit are
@@ -65,6 +66,16 @@ lib_deps =
     arduino-libraries/SD
     adafruit/RTClib
 
+; Lean pass-through variant: keeps the Maths CPU powered on and provides
+; bidirectional raw serial passthrough to the Iridium modem from the USB
+; console.  Excludes the full wii5_buoy main (pio_main.cpp) so setup()/loop()
+; come from pio_main_passthrough.cpp instead.
+[env:wii5_passthrough]
+extends = env:wii5_buoy
+build_src_filter =
+    +<*.cpp>
+    -<pio_main.cpp>
+
 ; LoRa-enabled variant (experimental). This path additionally depends on the
 ; Sh3dNode networking stack (sh3dNodeNetwork / SH3D_NODE_Packet_* / RH_RF95),
 ; which is NOT bundled in this repository, so the env does not build as-is.