Initial commit: Simple Sensor firmware for Heltec T114 with BME280

- MeshCore-based Simple Sensor firmware
- Heltec T114 without display
- BME280 sensor support (temp/humidity/pressure)
- Radio: 868.856018 MHz, SF7, BW62.5 kHz, CR4/7
- 2-byte path hash
- PlatformIO project

merge-bin.py

@@ -0,0 +1,48 @@
+#!/usr/bin/python3
+
+# Adds PlatformIO post-processing to merge all the ESP flash images into a single image.
+
+import os
+
+Import("env", "projenv")
+
+board_config = env.BoardConfig()
+firmware_bin = "${BUILD_DIR}/${PROGNAME}.bin"
+merged_bin = os.environ.get("MERGED_BIN_PATH", "${BUILD_DIR}/${PROGNAME}-merged.bin")
+
+
+def merge_bin_action(source, target, env):
+    flash_images = [
+        *env.Flatten(env.get("FLASH_EXTRA_IMAGES", [])),
+        "$ESP32_APP_OFFSET",
+        source[0].get_abspath(),
+    ]
+    merge_cmd = " ".join(
+        [
+            '"$PYTHONEXE"',
+            '"$OBJCOPY"',
+            "--chip",
+            board_config.get("build.mcu", "esp32"),
+            "merge_bin",
+            "-o",
+            merged_bin,
+            "--flash_mode",
+            board_config.get("build.flash_mode", "dio"),
+            "--flash_freq",
+            "${__get_board_f_flash(__env__)}",
+            "--flash_size",
+            board_config.get("upload.flash_size", "4MB"),
+            *flash_images,
+        ]
+    )
+    env.Execute(merge_cmd)
+
+
+env.AddCustomTarget(
+    name="mergebin",
+    dependencies=firmware_bin,
+    actions=merge_bin_action,
+    title="Merge binary",
+    description="Build combined image",
+    always_build=True,
+)