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  • Case ID: 288337
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How to Create an Instance of RPC (Remote Procedural Call) using the NRF52840

user24036

Hello,

I'm using SDK 17.0.2 with S113, v7.2.0 on the NRF52840. We currently have an instance of CLI running in our executive loop, and it works fine. We'd also like to implement RPC as well for calling functions from a remote processor. 

This is what we have so far:

    // Entering executive loop. Please note, the system WILL NOT EXIT this loop
    // unless a reset occurs.
    for ( ;; )
    {

        if (getRpcActivateFlagStatus())
        {   
            // Then service the RPC bytes!
            rpcServerBytePull(); // Not working
        }
        else
        {
             nrf_cli_process(&m_cli_uart); // Working fine
        }

        idle_state_handle();
             
        // Handle all of the events that were scheduled in the EMQ per
        // iteration of our executive loop. Please note, this is an nRF
        // driver-level API, which dispatches all pushed events to the system
        // EMQ (Event Message Queue).
        app_sched_execute();

    }

Is there a special HW flag in sdk_config.h that needs to be set in order for RPC to operate on UART? My sdk_config.h already enables UART by the way. Also, are there any examples of RPC that I can follow as our SDK does. not come with an RPC example.

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  • 0 in reply to user24036

    There is an implementation for __getChar() in the stdio retarget layer in the SDK (components\libraries\uart\retarget.c):

    #elif defined(__GNUC__) && defined(__SES_ARM)

int __getchar(FILE * p_file)
{
    uint8_t input;
    while (app_uart_get(&input) == NRF_ERROR_NOT_FOUND)
    {
        // No implementation needed.
    }
    return input;
}

    I'm assuming that the call to SEGGER_RTT_WaitKey() that you are seeing is from the SEGGER_RTT_Syscalls_SES.c file:

    /********************************************************************* 
*
*       __getchar()
*
*  Function description
*    Wait for and get a character via RTT.
*/
int __getchar() {
  return SEGGER_RTT_WaitKey();
}

    If you include and enable the UART retarget layer in your sdk_config.h file, the __getChar implementation in SEGGER_RTT_Syscalls_SES.c should be excluded by the "#if !defined(RETARGET_ENABLED) || RETARGET_ENABLED == 0"

    // <q> RETARGET_ENABLED  - retarget - Retargeting stdio functions
 

#ifndef RETARGET_ENABLED
#define RETARGET_ENABLED 1
#endif

    Best regards,
    Jørgen

  • 0 in reply to user24036

    I think I see the issue here. I'm using a CLI over UART transport layer. Can CLU over UART support commands that are non-strings? For instance, byte-packed Structs as commands.

  • 0 in reply to user24036

    The CLI library uses strcmp() to check for matching commands. If the commands are not in string format (with a \0 string terminator), this will likely fail.

    The UART peripheral/transport can support any byte-data, but you need to handle the received data correctly in the application.

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