nucleo

star 5

STM32 Nucleo H723ZG: hardware topology, firmware, CLI, shell commands, radio protocol handling. Use PROACTIVELY whenever discussing hardware, serial ports, USB devices, flashing, DFU, firmware, or any physical connection.

alxgmpr By alxgmpr schedule Updated 4/4/2026
play_arrow Run Skill in Manus View GitHub

name: nucleo description: "STM32 Nucleo H723ZG: hardware topology, firmware, CLI, shell commands, radio protocol handling. Use PROACTIVELY whenever discussing hardware, serial ports, USB devices, flashing, DFU, firmware, or any physical connection." metadata: author: alexgompper version: "2.0.0" user_invocable: false

STM32 Nucleo H723ZG — Hardware & Firmware Reference

Hardware Topology — READ BEFORE ANY HARDWARE DISCUSSION

  CC1101 (SPI3)  ───┐                                 ┌── USART3 (ST-LINK VCP) → serial shell
  433 MHz CCA       ├── STM32H723ZG Nucleo-144 ───────┤
  nRF52840 (USART2)─┘   FreeRTOS + lwIP               ├── Ethernet (LAN8742A) → TCP/UDP :9433
  802.15.4 CCX           ARM Cortex-M7 @ 550 MHz       └── UDP stream → CLI (cli/nucleo.ts)

Physical Devices

1. STM32 Nucleo H723ZG (the "Nucleo")

  • What: Main development board, ARM Cortex-M7 @ 550 MHz, runs FreeRTOS + lwIP
  • Connection to Mac: USB (ST-LINK) → /dev/tty.usbmodem* (serial shell at 115200 baud)
  • Connection to Mac: Ethernet → 10.0.0.3 (TCP/UDP port 9433 for CLI + stream)
  • Has attached: CC1101 (SPI3) and nRF52840 dongle (USART2)
  • Flash method: cd firmware && make flash (OpenOCD via ST-LINK). NEVER use st-flash.
  • Reset: reboot shell command or make reset from host

2. nRF52840 Dongle — NCP (soldered to Nucleo)

  • What: 802.15.4 radio for Thread/CCX, runs OpenThread NCP firmware
  • 4 wires to Nucleo: VCC, GND, TX (P0.20 → STM32 PD6), RX (P0.24 ← STM32 PD5)
  • UART: USART2 at 460800 baud, Spinel/HDLC protocol, NO hardware flow control
  • Connection to Mac: NONE — USB port exists on dongle but is NOT plugged into the Mac
  • The dongle's USB port is ONLY used for DFU recovery (flashing NCP firmware)
  • DFU bootloader: Red pulsing LED = stuck in bootloader, NOT running NCP firmware
  • Normal operation: No red LED, communicates over UART only
  • EUI-64: F4:CE:36:70:D6:82:E5:33
  • NCP firmware source: ~/lutron-tools/src/ot-nrf528xx/ (see NCP Firmware section below)
  • Pre-built DFU zip: firmware/ncp/ot-ncp-ftd-dfu.zip (ready to flash, known working)

3. nRF52840 Dongle — Sniffer/RCP (separate, USB to Mac)

  • What: Second nRF52840 dongle, used for either 802.15.4 sniffing (Wireshark) or OpenThread RCP (ot-daemon)
  • Connection to Mac: USB → /dev/cu.usbmodem* or /dev/tty.usbmodem*
  • NOT connected to the Nucleo — this is a standalone USB dongle
  • Firmware options: Sniffer mode (/nrf sniffer) or RCP mode (/nrf ot)
  • DFU: Press reset button → red LED pulses → flash via nrfutil nrf5sdk-tools dfu usb-serial

CRITICAL DISTINCTIONS

NCP Dongle (on Nucleo) Sniffer/RCP Dongle (USB)
Connected to STM32 via UART (4 wires soldered) Mac via USB
USB to Mac? NO (only for DFU recovery) YES
Serial port on Mac None (goes through Nucleo) /dev/cu.usbmodem*
Firmware OpenThread NCP Sniffer or RCP
Purpose Thread mesh member, TX/RX Passive capture or CLI
Red LED = DFU Must plug USB to Mac to fix Press reset, flash via USB

Serial Port Guide

Port Device
/dev/tty.usbmodem* (when only Nucleo connected) STM32 ST-LINK VCP (shell)
/dev/cu.usbmodem* (when sniffer dongle plugged in) nRF52840 sniffer/RCP dongle
If TWO usbmodem ports appear One is ST-LINK, other is sniffer dongle

The NCP dongle does NOT appear as a serial port on the Mac — it talks to the STM32 over UART, and you interact with it through the Nucleo's shell commands (ot, ccx, spinel).

Common Mistakes to AVOID

  1. DO NOT assume /dev/tty.usbmodem* is the nRF52840 — it's almost always the STM32 ST-LINK
  2. DO NOT try to flash the NCP dongle via Mac serial commands — it's not connected via USB
  3. DO NOT confuse the two nRF52840 dongles — one is soldered to the Nucleo (NCP), the other is a separate USB device (sniffer/RCP)
  4. DO NOT use nrfutil to flash the NCP dongle unless its USB is physically plugged into the Mac
  5. DO NOT send ot reset from the shell — it has been removed, but NEVER re-add it
  6. DO NOT rebuild the NCP firmware without using the EXACT build commands from firmware/PROJECT.md
  7. DO NOT use the script/build wrapper in ot-nrf528xx — use the direct cmake invocation

Radio Hardware

  • CC1101: 433 MHz FSK transceiver for CCA (Clear Connect Type A). SPI3 (PC10 SCK, PC11 MISO, PC12 MOSI, PA4 CS), GDO0 interrupt (PA0), GDO2 backup interrupt (PC15).
  • nRF52840: 802.15.4 radio for CCX (Clear Connect Type X / Thread). USART2 (PD5 TX, PD6 RX) at 460800 baud, Spinel/HDLC NCP protocol. This is a dongle soldered to the Nucleo — its USB is NOT connected to the Mac.
  • Ethernet: LAN8742A PHY, lwIP TCP/IP stack. Nucleo IP: 10.0.0.3.
  • USART3: ST-LINK Virtual COM Port — interactive shell with line editing and history.

Building & Flashing

IMPORTANT: Never use st-flash. Always use make flash (OpenOCD).

cd firmware

# Build (debug)
make build

# Build + flash via OpenOCD
make flash

# Release build
make release

# Reset without reflash
make reset

Build system: CMake with ARM GCC toolchain. Sources listed in firmware/CMakeLists.txt. OpenOCD config: firmware/openocd.cfg. Output ELF: firmware/build/lutron-nucleo.elf.

FreeRTOS Tasks

Task File Priority Purpose
cca_task firmware/src/cca/cca_task.cpp 3 CC1101 RX/TX, CCA packet processing, command queue
ccx_task firmware/src/ccx/ccx_task.cpp 3 nRF52840 Spinel NCP, Thread join, CCX multicast + CoAP unicast
stream_task firmware/src/net/stream.cpp 2 UDP packet stream to CLI clients (port 9433, binary framing)
shell_task firmware/src/shell/shell.cpp 1 UART interactive shell
eth_task firmware/src/net/eth.c 2 lwIP Ethernet, link polling

Shell Commands (UART + CLI passthrough)

Top-level

Command Description
status CC1101 state, RSSI, packet counts, heap, uptime
rx on|off Enable/disable CCA RX
tx <hex> Transmit raw CCA packet (hex bytes)
cca [cmd] CCA radio commands
ccx [cmd] CCX Thread commands
ot [cmd] OpenThread NCP query/control
spinel [cmd] Raw Spinel property access
stream UDP stream status
eth Ethernet PHY debug
config Show stored flash settings
save Save settings to flash
reboot NVIC_SystemReset

CCA subcommands (cca ...)

Command Description
cca button <dev_id_hex> <name> Button press (on/off/fav/raise/lower/scene1-4)
cca level <zone_hex> <target_hex> <%> [fade_qs] Bridge set-level
cca broadcast <zone_hex> <%> [fade_qs] Broadcast level to all devices
cca pico-level <dev_id_hex> <%> Pico level control
cca state <dev_id_hex> <%> State report
cca beacon <dev_id_hex> [dur] Discovery beacon
cca unpair <zone_hex> <target_hex> Unpair device
cca led <zone_hex> <target_hex> <0-3> LED config
cca fade <zone_hex> <target_hex> <on_qs> <off_qs> Fade config
cca trim <zone_hex> <target_hex> <hi%> <lo%> Trim config
cca phase <zone_hex> <target_hex> <byte_hex> Phase config
cca save-fav <dev_id_hex> Save favorite level
cca vive-level <hub_hex> <zone_hex> <%> [fade] Vive set-level
cca vive-raise/lower <hub_hex> <zone_hex> Vive dim
cca vive-pair <hub_hex> <zone_hex> [dur] Vive pairing
cca pair pico <dev_hex> [type] [dur] Pico pairing (5btn/2btn/4btn-rl/4btn-scene)
cca pair bridge <id_hex> <target_hex> [dur] Bridge pairing
cca identify <target_hex> Flash device LED
cca query <target_hex> Query device component info
cca tune ... CC1101 register/tuning debug
cca log [on|off] CCA RX UART log toggle

CCX subcommands (ccx ...)

Command Description
ccx Thread status (role, RX/TX counts)
ccx on <zone> Send ON to zone (multicast)
ccx off <zone> Send OFF to zone
ccx level <zone> <0-100> Set level % (multicast)
ccx scene <id> Recall scene
ccx peers List known Thread peers (RLOC16 → serial)
ccx promisc [on|off] Promiscuous mode (raw 802.15.4 frames)
ccx log [on|off] CCX RX UART log toggle
ccx coap preset <addr> <dev_id> <preset_id> <level%> [fade_s] CoAP preset programming
ccx coap aha <addr> <k4> <k5> CoAP AHA LED brightness
ccx coap get <addr> <uri_path> CoAP GET
ccx coap put <addr> <uri_path> <hex_payload> CoAP PUT
ccx coap post <addr> <uri_path> <hex_payload> CoAP POST

CCX address resolution (<addr> argument)

The CoAP commands accept addresses in three formats:

  • Full IPv6: fd0d:02ef:a82c:0000:abcd:1234:5678:9abc
  • RLOC shorthand: rloc:2C0C → builds full RLOC IPv6 from mesh-local prefix
  • Serial lookup: serial:72200096 → looks up RLOC from peer table

OT subcommands (ot ...)

Command Description
ot Thread state, RLOC16, partition ID
ot extaddr Get NCP EUI-64
ot eui64 Get factory EUI-64
ot channel Get/set channel
ot panid Get/set PAN ID
ot masterkey Get/set network master key
ot extpanid Get/set extended PAN ID
ot rloc16 Get RLOC16
ot leaderdata Get leader data
ot netdata Get network data
ot addrtable Get address table
ot ifconfig [up|down] Interface up/down
ot thread [start|stop] Thread start/stop
ot reset DANGEROUS — can brick NCP into DFU bootloader. NEVER USE.

CLI (Host Side)

# Connect to Nucleo
npx tsx cli/nucleo.ts              # uses NUCLEO_HOST env var
npx tsx cli/nucleo.ts 10.0.0.3   # direct IP

# Environment
NUCLEO_HOST=10.0.0.3             # default Nucleo IP

The CLI connects over UDP port 9433. Features:

  • Interactive shell mirroring all firmware commands
  • Live CCA/CCX packet display with protocol decoding
  • Prefix ! or use pass to send raw text to STM32 shell
  • record / stop for CSV packet capture
  • status queries firmware status blob
  • Auto-reconnect on disconnect
  • LEAP data integration for zone/device name lookups

Key Firmware Source Files

File Purpose
firmware/src/cca/cca_task.cpp CCA RX/TX task, command queue, packet processing
firmware/src/cca/cc1101.c CC1101 SPI driver, register config, RX/TX
firmware/src/cca/cca_tdma.cpp TDMA timing, slot tracking
firmware/src/cca/cca_commands.cpp CCA command builders (button, level, pair, config)
firmware/src/cca/cca_pairing.cpp CCA pairing engine (bridge, pico, vive, hybrid)
firmware/src/ccx/ccx_task.cpp CCX task: Thread join, multicast TX, CoAP unicast, peer table
firmware/src/ccx/coap.c CoAP message builder (GET/PUT/POST with CBOR payload)
firmware/src/ccx/ipv6_udp.c IPv6/UDP packet construction, checksum
firmware/src/ccx/ccx_msg.c CCX CBOR message encoder (LEVEL_CONTROL, SCENE_RECALL)
firmware/src/ccx/ccx_cbor.c Minimal CBOR encoder
firmware/src/ccx/smp_serial.c SMP DFU over Spinel (nRF firmware update)
firmware/src/net/stream.cpp UDP stream server (binary framing, multi-client)
firmware/src/net/eth.c lwIP Ethernet init, link management
firmware/src/shell/shell.cpp UART shell with line editing, history, all commands
firmware/src/storage/flash_store.cpp Flash persistence (device IDs, Thread credentials)

Protocol Encoding Quick Reference

CCA

  • Packet types: 0x80-0x9F = 24 bytes (22 data + 2 CRC), 0xA0+ = 53 bytes (51 data + 2 CRC)
  • Level encoding: level16 = percent * 0xFEFF / 100
  • Fade encoding: byte = seconds * 4 (quarter-seconds)
  • IDs are 32-bit hex (device_id, zone_id, target_id)

CCX

  • Multicast: UDP to ff03::1 port 9190, CBOR payload
  • LEVEL_CONTROL: [0, { 0: {0: level, 3: fade, 4: delay}, 1: [16, zoneId], 5: seq }]
  • SCENE_RECALL: [1, { 1: sceneId, 5: seq }]
  • CoAP unicast: port 5683, to device primary ML-EID
  • AHA LED brightness: path /cg/db/ct/c/AHA, payload [108, {4: <active>, 5: <inactive>}]
  • Level encoding same as CCA: level16 = percent * 0xFEFF / 100
  • Zone type always 16 in LEVEL_CONTROL key 1

NCP Firmware — Build & Recovery

Pre-built (use this first)

A known-working DFU zip is saved at firmware/ncp/ot-ncp-ftd-dfu.zip.

Recovering NCP from DFU Bootloader (Red Pulsing LED)

  1. Plug the NCP dongle's USB into the Mac — appears as /dev/tty.usbmodemXXXX
  2. Flash: nrfutil nrf5sdk-tools dfu usb-serial -pkg firmware/ncp/ot-ncp-ftd-dfu.zip -p /dev/tty.usbmodemXXXX
  3. Unplug dongle USB from Mac
  4. Reboot the Nucleo (reboot command or power cycle)
  5. Wait ~45s for NCP probe + Thread join + router promotion

Building from source (only if needed)

Source: ~/lutron-tools/src/ot-nrf528xx/

Key config in src/nrf52840/transport-config.h (must be modified from defaults):

#define UART_HWFC_ENABLED 0     // disabled (default is 1)
#define UART_PIN_TX 20          // P0.20 (default is 6 = LED1!)
#define UART_PIN_RX 24          // P0.24 (default is 8 = LED2!)

Build commands (EXACT — do not change):

export PATH="/Applications/ArmGNUToolchain/15.2.rel1/arm-none-eabi/bin:$PATH"
cd ~/lutron-tools/src/ot-nrf528xx
cmake -B build -GNinja \
  -DCMAKE_TOOLCHAIN_FILE=src/nrf52840/arm-none-eabi.cmake \
  -DCMAKE_BUILD_TYPE=Release \
  -DOT_APP_NCP=ON -DOT_APP_CLI=OFF -DOT_APP_RCP=OFF \
  -DOT_BOOTLOADER=USB -DNRF_PLATFORM=nrf52840 -DOT_PLATFORM=external \
  -DOT_UART_BAUDRATE=460800
ninja -C build ot-ncp-ftd

# Convert + package
arm-none-eabi-objcopy -O ihex build/bin/ot-ncp-ftd /tmp/ot-ncp-ftd-dfu.hex
nrfutil nrf5sdk-tools pkg generate \
  --hw-version 52 --sd-req 0x00 \
  --application /tmp/ot-ncp-ftd-dfu.hex \
  --application-version 7 \
  /tmp/ot-ncp-ftd-dfu.zip

CRITICAL build notes:

  • Must use -DOT_BOOTLOADER=USB — this selects the correct linker script (app at 0x1000, after MBR)
  • Using -DOT_BOOTLOADER=UART or no bootloader flag = app at 0x0000 = WILL NOT BOOT on PCA10059
  • Pins MUST be overridden in transport-config.h (defaults are P0.06/P0.08 which are LEDs)
  • The script/build wrapper does NOT work for our config — use cmake directly

Network

Host IP Purpose
Nucleo 10.0.0.3 STM32 (TCP/UDP :9433)
RA3 Processor 10.0.0.1 LEAP API (:8081), Thread border router
Caseta 10.0.0.2 LEAP API (:8081)
Designer VM 10.0.0.5 SSH (user/pass), Designer + SQL Server

Thread mesh-local prefix: fd0d:2ef:a82c:0::/64 Thread channel: 25, PAN ID:

Common Workflows

Build and flash firmware change

cd firmware && make flash

Test a CCA command

npx tsx cli/nucleo.ts
# In CLI: cca level <zone> <target> 50

Test a CCX command

npx tsx cli/nucleo.ts
# In CLI: ccx level <zone> 75

Send CoAP to a device

npx tsx cli/nucleo.ts
# In CLI: ccx coap aha fd0d:02ef:a82c:0000:XXXX:XXXX:XXXX:XXXX 150 20

Check Thread network status

npx tsx cli/nucleo.ts
# In CLI: ccx
# In CLI: ot
# In CLI: ccx peers

Debug CC1101 radio

npx tsx cli/nucleo.ts
# In CLI: status
# In CLI: cca tune show
# In CLI: cca tune reg get 0x04
Install via CLI
npx skills add https://github.com/alxgmpr/lutron-protocols --skill nucleo
Repository Details
star Stars 5
call_split Forks 1
navigation Branch main
article Path SKILL.md
More from Creator
alxgmpr
alxgmpr Explore all skills →