Example of downlink to modify tx interval?

WisBlock
1

Hi everyone, just wondering if there are any examples of code to send a downlink to modify the sleep time or LORAWAN_APP_INTERVAL of a wisblock module? I have successfully set up a 4-20mA pressure transducer with deep sleep, and would like the ability to modify the interval it sends an uplink…thanks in advance!

2

Hi Andy,

There is no ready to use example that would do that. But it is not that difficult to do it.

NOT TESTED, JUST OUT OF MY HEAD:

Step 1: Change LORAWAN_APP_INTERVAL from a define to a uint32_t

#define LORAWAN_APP_INTERVAL 20000

to

uint32_t LORAWAN_APP_INTERVAL = 20000;

Step 2: decode the downlink packet in void lorawan_rx_handler(lmh_app_data_t *app_data), set LORAWAN_APP_INTERVAL to the new value, set the timer to the new value and restart the timer.

void lorawan_rx_handler(lmh_app_data_t *app_data)
{
    Serial.printf("LoRa Packet received on port %d, size:%d, rssi:%d, snr:%d, data:%s\n",
          app_data->port, app_data->buffsize, app_data->rssi, app_data->snr, app_data->buffer);
    // Assuming the new time is encoded as 4 bytes. e.g. 3000000=> 0x00, 0x2D, 0xC6, 0xC0
    uint32_t new_time = app_data->buffer[0] << 24;
    new_time |= app_data->buffer[1] << 16;
    new_time |= app_data->buffer[2] << 8;
    new_time |= app_data->buffer[3];
    LORAWAN_APP_INTERVAL = new_time;
    TimerStop(&appTimer);
    TimerSetValue(&appTimer, LORAWAN_APP_INTERVAL);
    TimerStart(&appTimer);
}

Not sure what LoRaWAN Networks Server you use, but for example in Chirpstack the value needs to be encoded in Base64. 3000000 would be AC3GwA==
I use Base64 to hex to create the encoded data for Chirpstack.

As I said, above is not tested, but should work.
It might be a good idea to extend the downlink packet with some markers to make sure that the downlink is really a new interval value.

1 Like
3

Hi @beegee ,

I gave this a go this morning in the deep sleep example.

Had to change the SLEEP_TIME definition to LORAWAN_APP_INTERVAL which was no big deal.

But then getting the error

exit status 1
'appTimer' was not declared in this scope`

Any ideas?

I did try adding
TimerEvent_t appTimer;
up the top of lora_handler.cpp but then get this weird error which I have seen before when trying to edit code and don’t know what it means.

collect2.exe: error: ld returned 1 exit status
exit status 1
Error compiling for board WisBlock RAK4631.
4

Ah, different example.
In that code it is different.

In file main.h change

#define SLEEP_TIME 2 * 60 * 1000

to

uint32_t SLEEP_TIME = 2*60*1000;

In file lora_handler.cpp put the decoding into the function static void lorawan_rx_handler(lmh_app_data_t *app_data)

    case LORAWAN_APP_PORT:
      // Copy the data into loop data buffer
      memcpy(rcvdLoRaData, app_data->buffer, app_data->buffsize);
      rcvdDataLen = app_data->buffsize;
      eventType = 0;

      // Assuming the new time is encoded as 4 bytes. e.g. 3000000=> 0x00, 0x2D, 0xC6, 0xC0
      uint32_t new_time = app_data->buffer[0] << 24;
      new_time |= app_data->buffer[1] << 16;
      new_time |= app_data->buffer[2] << 8;
      new_time |= app_data->buffer[3];
      SLEEP_TIME = new_time;

      taskWakeupTimer.stop();
      taskWakeupTimer.setPeriod(SLEEP_TIME);
      taskWakeupTimer.start();

      // Notify task about the event
      if (taskEvent != NULL)
      {
#ifndef MAX_SAVE
        Serial.println("Waking up loop task");
#endif
        xSemaphoreGive(taskEvent);
      }
5

Thanks,

just changed those two things and get a compile error

multiple definition of SLEEP_TIME’; sketch\lora_handler.cpp.o:sketch/main.h:20: first defined here`

and then

collect2.exe: error: ld returned 1 exit status
exit status 1
Error compiling for board WisBlock RAK4631.
6

In main.h change

uint32_t SLEEP_TIME = 2*60*1000;

to

extern uint32_t SLEEP_TIME;

and then in lora_handler.cpp add

uint32_t SLEEP_TIME = 2*60*1000;

below the #include "main.h"

7

Great, thanks that is working once i worked out the port is 2

8

Perfect, thanks for the assistance @beegee!!

9

Hi, @beegee, I just came across another issue with my code, the 5801 isn’t going to sleep. The sensor itself seems to, but is there a way to shut the interface down? Current during sleep is in the order of 2mA, I would assume I should be able to get it down to 20 or so uA? When I physically disconnect it during operation, that’s about where it sits whilst in deep sleep.
Is there anything else I may need to do to reduce power consumption whilst in Deep Sleep?
This may be worthy of a new topic, which I’m happy to do if deemed appropriate.

10

This may be the fix…hadn’t started/stopped the 5801.
Is there anything else I may need to consider? Now sitting on around 22uA.

image

11

If you are at 22uA sleep current that is the best you can get. I never got my WisBlocks lower when using Arduino BSP which runs FreeRTOS in the background.

12

Excellent, thanks @beegee, hopefully my siblings christmas presents can now be completed!! Your help is as always much appreciated.
Andrew.