fix: grow app partitions to 1.5MB - C3 image no longer fits stock table

.github/workflows/release.yml

@@ -116,9 +116,13 @@ jobs:
 
       - name: Extract flash usage
         run: |
-          LINE=$(grep -oE 'Flash:[^(]*\(used [0-9]+ bytes from [0-9]+ bytes\)' build.log | tail -1)
-          USED=$(echo "$LINE" | grep -oE 'used [0-9]+' | grep -oE '[0-9]+')
-          TOTAL=$(echo "$LINE" | grep -oE 'from [0-9]+' | grep -oE '[0-9]+')
+          # Use the APPSIZE line (actual firmware.bin size vs app partition,
+          # from build/scripts/check_app_size.py) - NOT PlatformIO's "Flash:"
+          # figure, which omits MMU-alignment padding and understates the
+          # image the bootloader actually validates against the partition.
+          LINE=$(grep -oE 'APPSIZE: firmware\.bin is [0-9]+ bytes, app partition is [0-9]+ bytes' build.log | tail -1)
+          USED=$(echo "$LINE" | grep -oE '[0-9]+' | head -1)
+          TOTAL=$(echo "$LINE" | grep -oE '[0-9]+' | tail -1)
           mkdir -p meta
           echo "${{ matrix.env }}|${USED}|${TOTAL}" > meta/flash-${{ matrix.env }}.txt
           cat meta/flash-${{ matrix.env }}.txt
@@ -144,7 +148,7 @@ jobs:
             0x8000 .pio/build/${{ matrix.env }}/partitions.bin \
             0xe000 "${{ steps.tools.outputs.boot_app0 }}" \
             0x10000 .pio/build/${{ matrix.env }}/firmware.bin \
-            0x290000 .pio/build/${{ matrix.env }}/littlefs.bin
+            0x310000 .pio/build/${{ matrix.env }}/littlefs.bin
 
       - name: Copy app-only image
         run: |

build/scripts/check_app_size.py

@@ -0,0 +1,59 @@
+# FAIL THE BUILD IF firmware.bin DOES NOT FIT THE APP PARTITION
+#
+# PlatformIO's "Flash: X% (used N from M)" check sums ELF sections, but the
+# flashed .bin also contains MMU-alignment padding between mapped segments
+# (~113KB on ESP32-C3). The bootloader validates the *full image length*
+# against the app partition on every boot and refuses to boot an image that
+# spills past it - an endless rst:0x3 reset loop with no error visible on
+# USB-only boards. So the on-disk .bin size, not PlatformIO's figure, is the
+# number that matters.
+Import("env")
+
+import csv
+import os
+
+
+def get_app_partition_size():
+    partitions = env.BoardConfig().get("build.partitions", "default.csv")
+    path = partitions
+    if not os.path.isabs(path):
+        candidate = os.path.join(env.subst("$PROJECT_DIR"), partitions)
+        if os.path.exists(candidate):
+            path = candidate
+        else:
+            framework_dir = env.PioPlatform().get_package_dir(
+                "framework-arduinoespressif32"
+            )
+            path = os.path.join(framework_dir, "tools", "partitions", partitions)
+    sizes = []
+    with open(path) as f:
+        for row in csv.reader(f):
+            if not row or row[0].strip().startswith("#") or len(row) < 5:
+                continue
+            if row[1].strip() == "app":
+                sizes.append(int(row[4].strip(), 0))
+    if not sizes:
+        raise RuntimeError("No app partitions found in " + path)
+    return min(sizes), path
+
+
+def check_bin_size(source, target, env):
+    bin_path = env.subst("$BUILD_DIR/${PROGNAME}.bin")
+    bin_size = os.path.getsize(bin_path)
+    app_size, table = get_app_partition_size()
+    pct = bin_size / app_size * 100
+    print(
+        "APPSIZE: firmware.bin is %d bytes, app partition is %d bytes (%.1f%%)"
+        % (bin_size, app_size, pct)
+    )
+    if bin_size > app_size:
+        print(
+            "APPSIZE: ERROR - firmware.bin exceeds the app partition in %s by "
+            "%d bytes. The bootloader will refuse to boot this image "
+            "(silent rst:0x3 boot loop). Shrink the firmware or grow the app "
+            "partitions." % (table, bin_size - app_size)
+        )
+        env.Exit(1)
+
+
+env.AddPostAction("$BUILD_DIR/${PROGNAME}.bin", check_bin_size)

build/scripts/render_release_notes.py

@@ -10,9 +10,11 @@
 #
 # <meta-dir> holds flash-<env>.txt files, one per board, each a single line:
 #   <env>|<used-bytes>|<total-bytes>
-# produced by the release workflow parsing PlatformIO's "Flash: ... (used X from Y)"
-# output. We use PlatformIO's reported figure (not the on-disk firmware.bin size,
-# which includes chip-specific MMU-alignment padding and overstates usage).
+# produced by the release workflow parsing the APPSIZE line from
+# build/scripts/check_app_size.py: the on-disk firmware.bin size vs the app
+# partition size. The .bin size (including MMU-alignment padding) is what the
+# bootloader validates against the partition, so it is the honest figure -
+# PlatformIO's smaller "Flash:" number is what let an oversized C3 image ship.
 #
 # [ai-summary-file], if given and non-empty, is a short AI-generated summary of the
 # commit log (see release.yml's "AI release summary" step). Best-effort only - if

partitions_4MB.csv

@@ -0,0 +1,13 @@
+# Custom 4MB layout: app slots grown to 1.5MB (0x180000) each, filesystem
+# shrunk to 896KB (0xE0000). The stock default.csv's 1.25MB app slots are too
+# small for this firmware's ESP32-C3 image: the flashed .bin includes ~113KB
+# of MMU-alignment padding beyond PlatformIO's reported "Flash" figure, and
+# once the .bin exceeds the app partition the bootloader rejects the image on
+# every boot (endless rst:0x3 loop with no output on USB-only boards).
+# Name,   Type, SubType,  Offset,   Size,     Flags
+nvs,      data, nvs,      0x9000,   0x5000,
+otadata,  data, ota,      0xE000,   0x2000,
+app0,     app,  ota_0,    0x10000,  0x180000,
+app1,     app,  ota_1,    0x190000, 0x180000,
+spiffs,   data, spiffs,   0x310000, 0xE0000,
+coredump, data, coredump, 0x3F0000, 0x10000,

platformio.ini

@@ -17,12 +17,17 @@ data_dir=.pio/build/littlefs
 [env]
 framework=arduino
 board_build.filesystem=littlefs
+; Larger app slots than the stock table - see comment in partitions_4MB.csv.
+; NOTE: littlefs moved from 0x290000 to 0x310000; keep release.yml merge_bin
+; offsets in sync.
+board_build.partitions=partitions_4MB.csv
 platform=platformio/espressif32
 upload_protocol=esptool
 
 extra_scripts=
     pre:build/scripts/inject_version.py
     post:build/scripts/gzip_littlefs.py
+    post:build/scripts/check_app_size.py
 
 lib_deps=
     bblanchon/ArduinoJson@^7.3.1