Initial bare-metal foundation for nRF52840 PTT-FHSS
- Fully open toolchain: arm-none-eabi-gcc inside Podman/Docker container - Platform-agnostic build via justfile (auto-detects podman vs docker) - CMake + Ninja build system with arm-none-eabi toolchain file - nRF52840 linker script and startup with full 64-entry vector table - Register access via typed bitfield unions (include/regs.h) - FHSS channel sequencer: AES-128-ECB PRNG over 40 channels (2402-2480 MHz) - Low-power sleep via SYSTEM_ON WFI + GPIOTE wakeup on button press - Vendor deps as shallow git submodules: nrfx, CMSIS_5, tiny-AES-c
This commit is contained in:
Krzysztof Cieślik
41
src/fhss.c
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41
src/fhss.c
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#include "fhss.h"
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#include <aes.h>
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#define FHSS_CHANNELS 40u
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#define FHSS_DWELL_MS 2u
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/* TODO: replace with a real shared secret before deployment */
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static const uint8_t shared_key[16] = {
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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};
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static uint32_t slot;
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void fhss_init(void)
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{
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slot = 0u;
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}
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uint8_t fhss_next_channel(void)
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{
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uint8_t block[16] = {0};
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struct AES_ctx ctx;
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/* encode slot counter big-endian into the AES input block */
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block[0] = (uint8_t)(slot >> 24);
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block[1] = (uint8_t)(slot >> 16);
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block[2] = (uint8_t)(slot >> 8);
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block[3] = (uint8_t)(slot );
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AES_init_ctx(&ctx, shared_key);
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AES_ECB_encrypt(&ctx, block); /* encrypts block in-place */
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slot++;
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return block[0] % FHSS_CHANNELS;
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}
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void fhss_sync_tick(void)
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{
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slot++;
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}
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15
src/main.c
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15
src/main.c
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#include "radio.h"
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#include "fhss.h"
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#include "power.h"
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int main(void)
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{
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power_init();
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radio_init();
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fhss_init();
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while (1) {
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power_sleep_until_button();
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radio_tx_burst();
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}
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}
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37
src/power.c
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37
src/power.c
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#include "power.h"
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#include "regs.h"
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#include <nrf52840.h>
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#include <cmsis_gcc.h>
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/* P0.02 on XIAO BLE - adjust to match your schematic */
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#define BUTTON_PIN 2u
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void power_init(void)
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{
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/* DC/DC converter has lower quiescent current than the LDO */
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NRF_POWER->DCDCEN = 1u;
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NRF_GPIOTE->CONFIG[0] = (gpiote_config_t){
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.bit = {
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.MODE = GPIOTE_MODE_EVENT,
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.PSEL = BUTTON_PIN,
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.PORT = 0u,
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.POLARITY = GPIOTE_POL_LOTOHI,
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}
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}.reg;
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NRF_GPIOTE->INTENSET = (gpiote_inten_t){ .bit.IN0 = 1u }.reg;
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NVIC_EnableIRQ(GPIOTE_IRQn);
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}
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void power_sleep_until_button(void)
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{
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NRF_POWER->TASKS_LOWPWR = 1u;
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__WFI();
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}
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void GPIOTE_IRQHandler(void)
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{
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NRF_GPIOTE->EVENTS_IN[0] = 0u;
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}
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27
src/radio.c
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27
src/radio.c
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#include "radio.h"
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#include "fhss.h"
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#include "regs.h"
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#include <nrf52840.h>
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void radio_init(void)
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{
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/* TODO: configure RADIO peripheral (MODE, PCNF0/1, BASE/PREFIX, CRC) */
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}
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void radio_set_channel(uint8_t ch)
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{
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NRF_RADIO->FREQUENCY = (radio_frequency_t){
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.bit = { .FREQUENCY = ch, .MAP = RADIO_MAP_DEFAULT }
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}.reg;
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}
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void radio_tx(const uint8_t *data, uint8_t len)
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{
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(void)data; (void)len;
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/* TODO: load packet, enable TX, wait for END event, disable */
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}
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void radio_tx_burst(void)
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{
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/* TODO: hop + TX loop driven by fhss_next_channel() */
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}
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168
src/startup.c
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168
src/startup.c
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#include <stdint.h>
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/* linker script symbols */
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extern uint32_t _sidata; /* load address of .data in Flash */
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extern uint32_t _sdata; /* start of .data in RAM */
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extern uint32_t _edata; /* end of .data in RAM */
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extern uint32_t _sbss;
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extern uint32_t _ebss;
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extern uint32_t _estack; /* address equals initial SP value */
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extern int main(void);
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void Reset_Handler(void);
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static void __attribute__((used)) Default_Handler(void)
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{
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while (1);
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}
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/* ARM Cortex-M4 core exceptions */
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void NMI_Handler(void) __attribute__((weak, alias("Default_Handler")));
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void HardFault_Handler(void) __attribute__((weak, alias("Default_Handler")));
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void MemManage_Handler(void) __attribute__((weak, alias("Default_Handler")));
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void BusFault_Handler(void) __attribute__((weak, alias("Default_Handler")));
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void UsageFault_Handler(void) __attribute__((weak, alias("Default_Handler")));
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void SVC_Handler(void) __attribute__((weak, alias("Default_Handler")));
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void DebugMon_Handler(void) __attribute__((weak, alias("Default_Handler")));
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void PendSV_Handler(void) __attribute__((weak, alias("Default_Handler")));
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void SysTick_Handler(void) __attribute__((weak, alias("Default_Handler")));
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/* nRF52840 peripheral IRQs (IRQ0-IRQ47) */
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void POWER_CLOCK_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void RADIO_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void UARTE0_UART0_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void SPIM0_SPIS0_TWIM0_TWIS0_SPI0_TWI0_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void SPIM1_SPIS1_TWIM1_TWIS1_SPI1_TWI1_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void NFCT_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void GPIOTE_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void SAADC_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void TIMER0_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void TIMER1_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void TIMER2_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void RTC0_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void TEMP_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void RNG_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void ECB_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void CCM_AAR_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void WDT_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void RTC1_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void QDEC_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void COMP_LPCOMP_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void SWI0_EGU0_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void SWI1_EGU1_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void SWI2_EGU2_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void SWI3_EGU3_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void SWI4_EGU4_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void SWI5_EGU5_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void TIMER3_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void TIMER4_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void PWM0_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void PDM_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void MWU_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void PWM1_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void PWM2_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void SPIM2_SPIS2_SPI2_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void RTC2_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void I2S_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void FPU_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void USBD_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void UARTE1_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void QSPI_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void CRYPTOCELL_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void PWM3_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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void SPIM3_IRQHandler(void) __attribute__((weak, alias("Default_Handler")));
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/* vector table: 64 entries (16 core + 48 IRQs) */
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typedef void (*vector_fn)(void);
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__attribute__((section(".isr_vector"), used))
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const vector_fn vectors[64] = {
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/* 0 */ (vector_fn)&_estack,
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/* 1 */ Reset_Handler,
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/* 2 */ NMI_Handler,
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/* 3 */ HardFault_Handler,
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/* 4 */ MemManage_Handler,
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/* 5 */ BusFault_Handler,
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/* 6 */ UsageFault_Handler,
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/* 7 */ 0,
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/* 8 */ 0,
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/* 9 */ 0,
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/* 10 */ 0,
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/* 11 */ SVC_Handler,
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/* 12 */ DebugMon_Handler,
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/* 13 */ 0,
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/* 14 */ PendSV_Handler,
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/* 15 */ SysTick_Handler,
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/* IRQ0 */ POWER_CLOCK_IRQHandler,
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/* IRQ1 */ RADIO_IRQHandler,
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/* IRQ2 */ UARTE0_UART0_IRQHandler,
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/* IRQ3 */ SPIM0_SPIS0_TWIM0_TWIS0_SPI0_TWI0_IRQHandler,
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/* IRQ4 */ SPIM1_SPIS1_TWIM1_TWIS1_SPI1_TWI1_IRQHandler,
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/* IRQ5 */ NFCT_IRQHandler,
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/* IRQ6 */ GPIOTE_IRQHandler,
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/* IRQ7 */ SAADC_IRQHandler,
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/* IRQ8 */ TIMER0_IRQHandler,
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/* IRQ9 */ TIMER1_IRQHandler,
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/* IRQ10 */ TIMER2_IRQHandler,
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/* IRQ11 */ RTC0_IRQHandler,
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/* IRQ12 */ TEMP_IRQHandler,
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/* IRQ13 */ RNG_IRQHandler,
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/* IRQ14 */ ECB_IRQHandler,
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/* IRQ15 */ CCM_AAR_IRQHandler,
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/* IRQ16 */ WDT_IRQHandler,
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/* IRQ17 */ RTC1_IRQHandler,
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/* IRQ18 */ QDEC_IRQHandler,
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/* IRQ19 */ COMP_LPCOMP_IRQHandler,
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/* IRQ20 */ SWI0_EGU0_IRQHandler,
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/* IRQ21 */ SWI1_EGU1_IRQHandler,
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/* IRQ22 */ SWI2_EGU2_IRQHandler,
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/* IRQ23 */ SWI3_EGU3_IRQHandler,
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/* IRQ24 */ SWI4_EGU4_IRQHandler,
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/* IRQ25 */ SWI5_EGU5_IRQHandler,
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/* IRQ26 */ TIMER3_IRQHandler,
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/* IRQ27 */ TIMER4_IRQHandler,
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/* IRQ28 */ PWM0_IRQHandler,
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/* IRQ29 */ PDM_IRQHandler,
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/* IRQ30 */ 0, /* reserved */
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/* IRQ31 */ 0, /* reserved */
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/* IRQ32 */ MWU_IRQHandler,
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/* IRQ33 */ PWM1_IRQHandler,
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/* IRQ34 */ PWM2_IRQHandler,
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/* IRQ35 */ SPIM2_SPIS2_SPI2_IRQHandler,
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/* IRQ36 */ RTC2_IRQHandler,
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/* IRQ37 */ I2S_IRQHandler,
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/* IRQ38 */ FPU_IRQHandler,
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/* IRQ39 */ USBD_IRQHandler,
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/* IRQ40 */ UARTE1_IRQHandler,
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/* IRQ41 */ QSPI_IRQHandler,
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/* IRQ42 */ CRYPTOCELL_IRQHandler,
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/* IRQ43 */ 0, /* reserved */
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/* IRQ44 */ 0, /* reserved */
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/* IRQ45 */ PWM3_IRQHandler,
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/* IRQ46 */ 0, /* reserved */
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/* IRQ47 */ SPIM3_IRQHandler,
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};
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/* Reset_Handler */
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void Reset_Handler(void)
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{
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/* copy .data initializers from Flash to RAM */
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uint32_t *src = &_sidata;
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uint32_t *dst = &_sdata;
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while (dst < &_edata) {
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*dst++ = *src++;
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}
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/* zero .bss */
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dst = &_sbss;
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while (dst < &_ebss) {
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*dst++ = 0u;
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}
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main();
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while (1);
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}
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