NRF9160 poll()

[Adev]

Hello guys,

I`m pretty new in socket programing, I have a question , is there any way to trigger an event for a file descriptor that is used in poll() function ? 

For example: when a timer expires I want to trigger an event that will be catched by my poll() function. 

I searched almost everywhere and did not found anything. 

Thank you. 

[Håkon Alseth]

Hi,

 

A good place to start when you're new to socket based APIs is to check the manuals in linux, by entering "man poll", or just googling "man <some socket operation>".

poll returned events cannot be a specific timer, but you can give poll() an input timeout, as done here in mqtt_simple: https://github.com/NordicPlayground/fw-nrfconnect-nrf/blob/master/samples/nrf9160/mqtt_simple/src/main.c#L407

 

Kind regards,

Håkon

[Adev]

Hello, I was working on this example, the operation I want to do is to recieve an message over serial and send it with mqtt_publish, the problem is that after I catch the message from serial in uart interruption, I call mqtt_publish and it get stucked there because whe are in ist and poll does not recieve socket events, the only solution I see is to declare another socket for serial messaging but I can`t figure how to trigger an event for this socket.

[Håkon Alseth]

Try scheduling the uart message to main context.

The "uart_callback" (you might have named it differently) will inherit the interrupt, and a socket based call doesn't work when called from interrupt functions.

 

The simplest way to schedule to main is to set a global boolean flag, like this pseudo code:

volatile bool uart_command_received;
u8_t my_uart_buffer[SOME_SIZE];

void uart_cb(..)
{
   /* if uart string received */
   uart_command_received = true;
   /* Copy to global buffer */
   memcpy(my_uart_buffer, buf, received_size);
}

int main(void)
{
....
  while (1)
    if (uart_command_received == true) {
      uart_command_received = false;
      u32_t ret = mqtt_publish(..);
      if (ret < 0) {
        /*handle errror*/
    }
  }
}

 

Kind regards,

Håkon

[Adev]

Yes that`s the first thing I tried, that worked but in main also I have the poll function with an timeout of 60 seconds, so I will have to wait for 60 seconds ( in worst case) every time I want to publish something :( .

[Håkon Alseth]

Then you can start a system work queue from the interrupt context:

https://docs.zephyrproject.org/1.9.0/kernel/threads/workqueues.html#system-workqueue

 

Kind regards,

Håkon