Here is a list of all files with brief descriptions:

main
fonts
font_icons_48.c
font_inter_14.c
font_inter_14_medium.c
font_pjs_20_medium.c
font_pjs_20_semibold.c
font_pjs_28_light.c
font_pjs_28_semibold.c
addr_check.h	Structural address checks for the config portal
assets.h	What each selectable asset IS — one row per pos_chain_t
boot.cpp	Bring-up: NVS, panel, reader, wallet, addresses, setup wizard, Wi-Fi and clock — everything before the main loop
card_io.cpp	The card on the reader: is it usable, open a channel, sign, read the payout addresses off it
card_status.h	What a tapped card is missing, read from its SELECT response
chain_icons.c
chain_icons.h
civil_time.cpp	TZ-independent calendar arithmetic and date-string parsing
civil_time.h	TZ-independent calendar arithmetic and date-string parsing
config_defaults.h	Config.h, plus a default for every key added after the first config.h files shipped — so an older config.h still builds
eth_addr.cpp	Implementation of the hex Ethereum-address parser, with EIP-55 checksum verification (HARDENING.md §7.1)
eth_addr.h	Hex Ethereum-address parsing — a pure, dependency-free unit so it can be unit-tested and fuzzed on the host (see fuzz/fuzz_parse_address.cpp)
eth_json.cpp	Implementation of the JSON-RPC response parsing helpers
eth_json.h	JSON-RPC response parsing helpers — kept in their own unit (cJSON + CW_Utils only, no ESP-IDF networking) so they can be fuzzed on the host (see fuzz/fuzz_eth_rpc_json.cpp)
eth_rlp.cpp	RLP encoder implementation for EIP-1559 (type 2) transactions
eth_rlp.h	Minimal RLP encoder for EIP-1559 (type 2) Ethereum transactions
eth_rpc.cpp	Ethereum JSON-RPC client implementation (HTTPS). Network bring-up (Wi-Fi, SNTP) lives in net.cpp
eth_rpc.h	Ethereum JSON-RPC client over HTTPS (nonce / ecrecover parity / raw-tx broadcast / receipt polling). Network bring-up (Wi-Fi, SNTP) lives in net.h
eth_sig.cpp	Secp256k1 verification + recovery bit, on mbedTLS's ECP module
eth_sig.h	The recovery bit of a secp256k1 signature, computed on the device
form_parse.h	Application/x-www-form-urlencoded field extraction
hardening.cpp	Anomaly handling (§3.3): local fail-closed + persisted counter and a RAM ring buffer for on-site inspection. Never bricks
hardening.h	Decision-integrity primitives (see docs/HARDENING.md §3, §4)
https_post.cpp	HTTPS JSON POST with the authenticated-Date clock cross-check
https_post.h	One HTTPS JSON POST, shared by every RPC client in the firmware
json_out.h	Escaping for values the config portal puts inside a JSON string
keccak256.cpp	Original (pre-NIST) Keccak-256 implementation, 0x01 padding
keccak256.h	Original Keccak-256 digest as used by Ethereum
logo_mid.c
logo_mid.h
main.cpp	Cryptnox-pos entry point: touchscreen USDC payment terminal
money.h	The sale's arithmetic: keypad cents, base units, wei, fees, calldata
net.cpp	Wi-Fi station bring-up (init/scan/connect/RSSI) and SNTP time sync
net.h	Network bring-up: Wi-Fi station (init/scan/connect/RSSI) and SNTP time sync. No application-protocol logic lives here — the Ethereum JSON-RPC client is in eth_rpc.h
ota.cpp	Firmware slot handling. See ota.h for the why
ota.h	Firmware slot handling: receive an image into the idle slot, verify it, and install it only once somebody accepts it on the panel
ota_version.h	Dotted version comparison, for deciding whether an update goes forwards or backwards
pay.cpp	What a sale is paid with and to, and the sale between broadcast and verdict
pay_evm.cpp	Ethereum and Polygon: endpoint, fees, pre-flight balance, sign and broadcast an EIP-1559 transfer
pay_tron.cpp	Tron: pre-flight balance, sign and broadcast a TRX or TRC-20 transfer
portal_fonts.h
portal_page.h	The config portal's document — the HTML/CSS half and the script half
pos_app.h	Private to the application files (main, boot, card_io, pay, pay_evm, pay_tron): the state they share and the calls between them
provision.cpp	The config portal: a SoftAP and a captive portal, for setup and for administration alike, one page for both. See provision.h for the why
provision.h	The config portal: one web app for setting a terminal up and for administering it afterwards, in two modes
rpc_error.h	Turn a node's JSON-RPC refusal into a line an operator can act on
settings.cpp	NVS-backed implementation of the persistent device settings
settings.h	Persistent device settings stored in NVS (backlight, Wi-Fi creds)
settings_rules.h	What a setting may be, apart from where it is stored
tap_icon.c
tap_icon.h
touch_cal.h	Touch arithmetic: two-point calibration, and the second-contact guard
tron_rpc.cpp	Tron HTTP API client implementation
tron_rpc.h	Tron HTTP API client (Nile testnet): build a TRX transfer, broadcast it signed, poll its receipt
tron_tx.cpp	Implementation of the Tron transaction hex helpers
tron_tx.h	Tron transaction hex helpers — protobuf varints, the TransferContract integrity check and the signed-Transaction envelope
ui.cpp	Touchscreen UI implementation built on LVGL 8.x
ui.h	Touchscreen UI API: screens, events and transaction states for the CYD (ILI9341 + XPT2046) payment flow
ui_admin.cpp	The settings page, touch calibration and the admin-code screens
ui_hal.cpp	Panel and touch hardware: TFT_eSPI flush, XPT2046 reads, the LVGL display and input drivers, backlight PWM
ui_internal.h	Private to the ui*.cpp files: the state and helpers they share
ui_sale.cpp	The sale flow: amount, confirm, PIN, transaction status, and their page chrome
ui_setup.cpp	First-run setup on the panel: welcome, the browser hand-off, card reads, Wi-Fi
ui_theme.cpp	Colours, the LVGL theme and the shared layout metrics
ui_widgets.cpp	Widget helpers shared by every screen, and the Wi-Fi signal mark
wdt.h	Task-watchdog feed that is safe to call from any task