Custom characteristic, update value for read

[Keith V]

I'm trying toa custom nRF52840 board using SDK 17.02 and SD 7.01

I create a read/Write only service, it shows up in nRF Connect just fine

I can write to the service using the NRFConnect app and catching the event BLE_GATTS_EVT_WRITE, then checking the handle to determine which characteristic got called.

That works, but how the heck do I save that value so when I do a read from the nRFConnet app I get that same value??

else if (p_evt_write->handle == p_mtgw->LoRSync_handles.value_handle)
    {

      uint16_t ScanRate;

      if(p_evt_write->len == 2)
      {
         ScanRate = uint16_big_decode(p_evt_write->data);
         BLEScanRateCallback(ScanRate);

         ble_gatts_value_t val;
         uint8_t data[2];

         uint16_big_encode(ScanRate, data);

         val.len = 2;
         val.offset = 0;
         val.p_value = data;
         ret_code_t err_code = sd_ble_gatts_value_set(BLE_CONN_HANDLE_INVALID/*p_ble_evt->evt.gatts_evt.conn_handle*/,  p_mtgw->LoRSync_handles.value_handle, &val);

         if (err_code == NRF_SUCCESS)
        {
            NRF_LOG_INFO("Sync rate has been updated: %x %x", data[0], data[1])

            // Save new battery value.
           // p_bas->battery_level_last = battery_level;
        }
        else
        {
            NRF_LOG_DEBUG("Error during Sync rate update: 0x%08X", err_code)

            return;// err_code;
        }

         NRF_LOG_INFO("Lora Sync Rate: %x", ScanRate);
      }
    }

[Karl Ylvisaker]

Hello,

That works, but how the heck do I save that value so when I do a read from the nRFConnet app I get that same value??

The ble_gatts_evt_write_t event structure will hold the written data in the data field, you can retrieve the written data from there.
What is your p_evt_write variable? Have you used the folloiwing initialization?

ble_gatts_evt_write_t const * p_evt_write = &p_ble_evt->evt.gatts_evt.params.write;

I am not sure what you are doing in the code snippet you have provided, with the ScanRate callback and big_encoding, but what does your logger output when you run this code? How does it differ from what you would have expected?

Best regards,
Karl