UA1ZBE Custom Firmware v1.0

Features:
- VFO mode with direct frequency input
- POCSAG decoder (512/1200 baud) with BCH(31,21) correction
- Full-screen Spectrum analyzer
- FM Radio receiver
- RSSI signal indicator overlay
- Custom boot splash (UA1ZBE / POCSAG pager / build date)

Architecture:
- app/mode.c — mode dispatcher (VFO/POCSAG/Spectrum/FM)
- app/boot_splash.c — 2-second boot splash
- app/pocsag/ — POCSAG decoder + BCH correction
- app/display_rssi.c — RSSI indicator
- main.c — entry point with custom init
- syscalls.c — bare-metal _sbrk stub

Build: arm-none-eabi-gcc -Os -flto -Wall -Werror -Wextra
Size: 57.9KB Flash / 3.6KB RAM

Controls:
- 0-9: Direct frequency input (VFO)
- SK2: POCSAG mode
- SK1: Spectrum analyzer
- 0: FM Radio
- EXIT: Return to VFO
- F/*: Toggle 512/1200 baud (in POCSAG)

hardware/dp32g030/crc.def

@@ -0,0 +1,58 @@
+# Copyright 2023 Dual Tachyon
+# https://github.com/DualTachyon
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+[CRC]
+@ = 0x40003000, 0x800
+
+CR = 0x0000
+> CRC_EN, 0, 1
+= DISABLE, 0
+= ENABLE, 1
+
+> INPUT_REV, 1, 1
+= NORMAL, 0
+= REVERSED, 1
+
+> INPUT_INV, 2, 2
+= NORMAL, 0
+= BIT_INVERTED, 1
+= BYTE_INVERTED, 2
+= BIT_BYTE_INVERTED, 3
+
+> OUTPUT_REV, 4, 1
+= NORMAL, 0
+= REVERSED, 1
+
+> OUTPUT_INV, 5, 2
+= NORMAL, 0
+= BIT_INVERTED, 1
+= BYTE_INVERTED, 2
+= BIT_BYTE_INVERTED, 3
+
+> DATA_WIDTH, 7, 2
+= 32, 0
+= 16, 1
+= 8, 2
+
+> CRC_SEL, 9, 2
+= CRC_16_CCITT, 0
+= CRC_8_ATM, 1
+= CRC_16, 2
+= CRC_32_IEEE802_3, 3
+
+IV = 0x0004
+DATAIN = 0x0008
+DATAOUT = 0x000C
+