Working with STM32

Hardware Connection

Connect according to the table below:

STM32 example programs are located in the examples/main_examples directory of Lora-net/usp.
Testing requires two Core2021-XF modules: one for transmission and one for reception.
The following describes several example programs, including usage and operational effects.

Example Description

Based on STM32L476RG + Core2021-XF, implements porting functionality verification examples
Used to test the following:
- SPI interface functionality
- Interrupt IRQ response
- Timers and low‑power modes
- Random number generation
- Radio configuration time
- MCU sleep time
- Flash emulation storage (optional)
Tests cover module initialization, TX/RX configuration, and MCU‑related hardware interfaces
Test results are printed via the serial port

Code Analysis

Hardware abstraction layers:
- smtc_modem_hal.h, smtc_hal_mcu.h, smtc_hal_gpio.h, smtc_hal_watchdog.h
- IRQ callback functions: radio_tx_irq_callback, radio_rx_irq_callback, timer_irq_callback
LoRa/Radio parameters:
- ralf_params_lora_t rx_lora_param / tx_lora_param: simulated RX/TX configurations for porting tests
- Fixed frequency, symbol rate, bandwidth, sync word, and transmit power
Main test functions:
- porting_test_spi(): Verifies SPI port and chip firmware version
- porting_test_radio_irq(): Verifies TX/RX interrupt triggering
- porting_test_get_time(): Checks HAL time‑getting function
- porting_test_timer_irq(): Verifies timer interrupts
- porting_test_stop_timer(): Verifies timer stop functionality
- porting_test_disable_enable_irq(): Verifies interrupt disable/enable logic
- porting_test_random(): Verifies random number generation and distribution
- porting_test_config_rx_radio() / porting_test_config_tx_radio(): Checks RX/TX configuration time
- porting_test_sleep_ms(): Checks MCU sleep time
- porting_test_timer_irq_low_power(): Verifies timer interrupts in low‑power mode
Flash tests (optional): porting_test_flash() / test_context_store_restore()
main_porting_tests():
- Initializes MCU peripherals
- Disables IRQs to avoid initialization conflicts
- Runs porting tests in a loop and optionally performs Flash tests based on ENABLE_TEST_FLASH
- After completion, enters an infinite loop and refreshes the watchdog

Operation Result

Example Description

Based on STM32L476RG + Core2021-XF, implements a Ping‑Pong + Periodic Uplink communication example
Supports Manager mode triggered by a user button:
- The Manager initiates a PING
- The Subordinate automatically responds with a PONG
- Callbacks are triggered automatically after each transmission or reception
Supports periodic uplink (sends a fixed payload "LoRa" every 10 seconds by default)
LED indicators for TX/RX status
Uses a watchdog to prevent MCU lock‑up
Automatically enters low‑power sleep to save energy

Code Analysis

MCU initialization:
- hal_mcu_init(): Initializes MCU peripherals
- smtc_rac_init(): Initializes the Radio Abstraction Layer
User button:
- user_button_t stores button state and press duration
- user_button_callback(): Debounces the button and triggers Manager mode
LED initialization: SMTC_LED_TX / SMTC_LED_RX
Application initialization:
- ping_pong_init(): Initializes Ping‑Pong transactions
- periodic_uplink_init(): Initializes periodic uplink
Main loop:
1. Reload watchdog: hal_watchdog_reload()
2. Run radio transactions: smtc_rac_run_engine()
3. Process button events: ping_pong_on_button_press()
4. MCU sleep: determine if there are pending transactions, then call hal_mcu_set_sleep_for_ms(SLEEP_DELAY)
Core logic:
- ping_pong_init(): Sets transaction context, payload, and modulation parameters
- ping_pong_tx() / ping_pong_rx(): Sends/receives PING or PONG
- pre_ping_pong_callback() / post_ping_pong_callback():
  - LED control
  - Handles transaction completion status (TX_DONE, RX_PACKET, RX_TIMEOUT, CRC_ERROR, TASK_ABORTED)
  - Automatically retries or restarts
Periodic uplink logic: schedules the next transmission via a callback function

Operation Result

Example Description

Based on STM32L476RG + Core2021-XF, implements:
- LoRaWAN OTAA join
- Periodic uplink
- Immediate uplink triggered by a user button
Uses example_options.h to provide LoRaWAN credentials:
- USER_LORAWAN_DEVICE_EUI
- USER_LORAWAN_JOIN_EUI
- USER_LORAWAN_GEN_APP_KEY
- USER_LORAWAN_APP_KEY
Region configuration: MODEM_EXAMPLE_REGION (EU868 or WW_2G4)
Watchdog and low‑power sleep protect the MCU
Serial port prints events, uplink/downlink data, and debug information

Code Analysis

Initialization:
- hal_mcu_init(), hal_gpio_init_in() configure peripherals
- smtc_rac_init() and smtc_modem_init() initialize the modem, with callback modem_event_callback()
User button:
- user_button_callback() handles button events and triggers an immediate uplink
Periodic uplink:
- periodical_uplink_init() initializes the transaction
- After each transmission, post_periodic_callback() schedules the next uplink
Event callback:
- modem_event_callback() handles various modem events:
  - RESET: sets credentials and region, initiates Join
  - JOINED: successful join, starts the first periodic uplink
  - ALARM: periodic uplink trigger
  - TXDONE: uplink transmission completed
  - DOWNDATA: downlink data received
  - Other events (LINK_CHECK, CLASS_B_PING_SLOT_INFO, etc.) print debug information
Uplink data:
- 32-bit uplink counter
- Optional port for transmission (default 101/102)
Main loop:
- Checks the button for immediate uplink
- Calls smtc_modem_run_engine() and smtc_rac_run_engine() to process transactions
- MCU sleeps until the next transaction or watchdog reload

Operation Result