A bare metal example of Inter Processor Communication (IPC) on nrf5340

RE: A bare metal example of Inter Processor Communication (IPC) on nrf5340

JonasForssell — Tue, 14 Oct 2025 06:32:33 GMT

Here is an update.
It works now. I summarize the solution below for anyone who is interested:

App core main()

  spu_configure();
  ipc_rx_configure();
  ipc_rx_recieve();

ipc_rx

volatile uint32_t __attribute__((section(".shared_memory"))) shared_value;


// Configure the app core to trigger an event every time a message is transmitted from network core
void ipc_rx_configure(void) {

  // Enable interrupt for RECEIVE[0]
  NRF_IPC_S->INTENSET = IPC_INTENSET_RECEIVE0_Msk;

  // Listen to channel 0
  NRF_IPC_S->RECEIVE_CNF[0] = 1;
  
  // Enable IPC interrupt in NVIC
  NVIC_EnableIRQ(IPC_IRQn);

  // Start up the network core
  NRF_RESET_S->NETWORK.FORCEOFF = RESET_NETWORK_FORCEOFF_FORCEOFF_Release;

}


void ipc_rx_recieve(void) {

  // From now on this will be interrupt driven so stay here
  while (1) {

    //__WFE();
    }

}

// This event will be triggered every time there is a message.
void IPC_IRQHandler(void) {
    if (NRF_IPC_S->EVENTS_RECEIVE[0]) {
        NRF_IPC_S->EVENTS_RECEIVE[0] = 0;

        printf("Message: ");
        printf("%u", shared_value);
        printf(" \n");
    
    }
}

spu

#define SPU_RAM_REGION_INDEX 31

void spu_configure(void) {
// In secure boot eller startup på application core
// Configure RAM region 31 (0x2003F000) as non-secure
NRF_SPU_S->RAMREGION[SPU_RAM_REGION_INDEX].PERM =
   (SPU_RAMREGION_PERM_READ_Msk |
    SPU_RAMREGION_PERM_WRITE_Msk |
    SPU_RAMREGION_PERM_SECATTR_Non_Secure << SPU_RAMREGION_PERM_SECATTR_Msk |
    SPU_RAMREGION_PERM_EXECUTE_Msk);    // SECATTR bit is 0 => non-secure

}

I have added a reference to the right memory area in the linker script for both network and application cores as

place at address 0x2003F000 { section .shared_memory };

//but for the network core I have also added
do not initialize                           { section .shared_memory };

// ...since the app core must unlock the area before the network core can write

Here is the network core

main()

 ipc_tx_configure();

 while(1) {
  delay_one_second();
  ipc_tx_transmit();
  }

ipc_tx

#define IPC_CHANNEL 0

volatile uint32_t __attribute__((section(".shared_memory"))) shared_value;

void ipc_tx_configure(void){

// Set up the IPC channel 0 to be used for trigger a signal to application core.
// We will only send on channel 0 (so we set bit 0 here)
    NRF_IPC_NS->SEND_CNF[IPC_CHANNEL] = 1;

}


void ipc_tx_transmit(void) {

    //Use the shared memory to send a message to the application core
    shared_value = 23;

    // Trigger IPC event on channel 0
    NRF_IPC_NS->TASKS_SEND[IPC_CHANNEL] = 1;


}

RE: A bare metal example of Inter Processor Communication (IPC) on nrf5340

JonasForssell — Mon, 13 Oct 2025 14:01:18 GMT

A small update.

I can get the interrupt to work now. The app core has to listen to channel 0 and the network core has to be started from the app core.

// Configure the app core to trigger an event every time a message is transmitted from network core
void ipc_rx_configure(void) {

  // Enable interrupt for RECEIVE[0]
  NRF_IPC_S->INTENSET = IPC_INTENSET_RECEIVE0_Msk;

  // Listen to channel 0
  NRF_IPC_S->RECEIVE_CNF[0] = 1;
  
  // Enable IPC interrupt in NVIC
  NVIC_EnableIRQ(IPC_IRQn);

  // Start up the network core
  NRF_RESET_S->NETWORK.FORCEOFF = RESET_NETWORK_FORCEOFF_FORCEOFF_Release;


}

Next up is to figure out how I can transfer a message through shared memory.

I read about that the IPC contains two registers for general purpose data GPMEM[0] and [1] but I cannot seem to get the data across to the other core.

On the network core I use NRF_IPC_NS->GPMEM[0] = 27;
and on the application core I try printf("Value %u", NRF_IPC_S->GPMEM[0]);

but the value does not seem to get across and stays at 0. Also in the debugger.
Any thoughts?

RE: A bare metal example of Inter Processor Communication (IPC) on nrf5340

JonasForssell — Mon, 13 Oct 2025 10:17:14 GMT

Thank you for your reply. I am not using Zephyr at all since this is bare metal.

RE: A bare metal example of Inter Processor Communication (IPC) on nrf5340

Turbo J — Mon, 13 Oct 2025 08:45:13 GMT

I don't see the required IRQ_CONNECT() macro in your code. Zephyr interrupt handlers are not called by name. Your program thus tries to to fire an unhandled interrupt which should trigger a corresponding fault.