Save downlink data for ESP32 lorawan

Ive been searching all day and on every other post ive found on here there was no actual explanation for how to save the downlink data from the ESP32_LoRaWAN master library into a global variable so that it may be used elsewhere in the program. Ive seen people try to answer this question by pasting the OTAA_LED example with no follow on explanation to how it works. I see that you can make case statements in the void app((uint8_t data); function, but the problem is that you cant call the app() function in other parts of the sketch. Any solutions?

this is the example im referring to.

/*
  • HelTec Automation™ LoRaWAN 1.0.2 OTAA example use OTAA, CLASS A
  • Function summary:
    • You can use port 4 to control the LED light.
    • If the issued value is 1(ASCII), the lamp will be lit.
    • The release value is 2(ASCII) and the light will be turned off.
    • use internal RTC(150KHz);
    • Include stop mode and deep sleep mode;
    • 15S data send cycle;
    • Informations output via serial(115200);
    • Only ESP32 + LoRa series boards can use this library, need a license
  • to make the code run(check you license here: http://www.heltec.cn/search/);
  • You can change some definition in “Commissioning.h” and “LoRaMac-definitions.h”
  • HelTec AutoMation, Chengdu, China.
  • 成都惠利特自动化科技有限公司
  • https://heltec.org
  • support@heltec.cn

*this project also release in GitHub:
*https://github.com/HelTecAutomation/ESP32_LoRaWAN
*/

#include <ESP32_LoRaWAN.h>
#include “Arduino.h”

/*license for Heltec ESP32 LoRaWan, quary your ChipID relevant license: http://resource.heltec.cn/search */
uint32_t license[4] = {0x4915A653,0xC69E42EE,0x0D9EA6D4,0xB5201468};

/* OTAA para*/
uint8_t DevEui[] = { 0x22, 0x32, 0x33, 0x00, 0x00, 0x88, 0x88, 0x02 };
uint8_t AppEui[] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
uint8_t AppKey[] = { 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x88, 0x66, 0x01 };

/* ABP para*/
uint8_t NwkSKey[] = { 0x15, 0xb1, 0xd0, 0xef, 0xa4, 0x63, 0xdf, 0xbe, 0x3d, 0x11, 0x18, 0x1e, 0x1e, 0xc7, 0xda,0x85 };
uint8_t AppSKey[] = { 0xd7, 0x2c, 0x78, 0x75, 0x8c, 0xdc, 0xca, 0xbf, 0x55, 0xee, 0x4a, 0x77, 0x8d, 0x16, 0xef,0x67 };
uint32_t DevAddr = ( uint32_t )0x007e6ae1;

/LoraWan channelsmask, default channels 0-7/
uint16_t userChannelsMask[6]={ 0x00FF,0x0000,0x0000,0x0000,0x0000,0x0000 };

/LoraWan Class, Class A and Class C are supported/
DeviceClass_t loraWanClass = CLASS_C;

/the application data transmission duty cycle. value in [ms]./
uint32_t appTxDutyCycle = 15000;

/OTAA or ABP/
bool overTheAirActivation = true;

/ADR enable/
bool loraWanAdr = true;

/* Indicates if the node is sending confirmed or unconfirmed messages */
bool isTxConfirmed = true;

/* Application port */
uint8_t appPort = 2;

/*!

  • Number of trials to transmit the frame, if the LoRaMAC layer did not
  • receive an acknowledgment. The MAC performs a datarate adaptation,
  • according to the LoRaWAN Specification V1.0.2, chapter 18.4, according
  • to the following table:
  • Transmission nb | Data Rate
  • ----------------|-----------
  • 1 (first) | DR
  • 2 | DR
  • 3 | max(DR-1,0)
  • 4 | max(DR-1,0)
  • 5 | max(DR-2,0)
  • 6 | max(DR-2,0)
  • 7 | max(DR-3,0)
  • 8 | max(DR-3,0)
  • Note, that if NbTrials is set to 1 or 2, the MAC will not decrease
  • the datarate, in case the LoRaMAC layer did not receive an acknowledgment
    */
    uint8_t confirmedNbTrials = 8;

/*LoraWan debug level, select in arduino IDE tools.

  • None : print basic info.
  • Freq : print Tx and Rx freq, DR info.
  • Freq && DIO : print Tx and Rx freq, DR, DIO0 interrupt and DIO1 interrupt info.
  • Freq && DIO && PW: print Tx and Rx freq, DR, DIO0 interrupt, DIO1 interrupt and MCU deepsleep info.
    */
    uint8_t debugLevel = LoRaWAN_DEBUG_LEVEL;

/LoraWan region, select in arduino IDE tools/
LoRaMacRegion_t loraWanRegion = ACTIVE_REGION;

#define LEDPin 25 //LED light
void app(uint8_t data)
{
// lora_printf(“data:%d\r\n”,data);
switch(data)
{
case 49:
{
pinMode(LEDPin,OUTPUT);
digitalWrite(LEDPin, HIGH);
break;
}
case 50:
{
pinMode(LEDPin,OUTPUT);
digitalWrite(LEDPin, LOW);
break;
}
case 51:
{
break;
}
default:
{
break;
}
}
}

void downLinkDataHandle(McpsIndication_t *mcpsIndication)
{
lora_printf("+REV DATA:%s,RXSIZE %d,PORT %d\r\n",mcpsIndication->RxSlot?“RXWIN2”:“RXWIN1”,mcpsIndication->BufferSize,mcpsIndication->Port);
lora_printf("+REV DATA:");
app(mcpsIndication->Buffer[0]);

for(uint8_t i=0;iBufferSize;i++)
{
lora_printf("%02X",mcpsIndication->Buffer[i]);
}
lora_printf("\r\n");
}

static void prepareTxFrame( uint8_t port )
{
appDataSize = 4;//AppDataSize max value is 64
appData[0] = 0x00;
appData[1] = 0x01;
appData[2] = 0x02;
appData[3] = 0x03;
}

// Add your initialization code here
void setup()
{
Serial.begin(115200);
while (!Serial);
SPI.begin(SCK,MISO,MOSI,SS);
Mcu.init(SS,RST_LoRa,DIO0,DIO1,license);
deviceState = DEVICE_STATE_INIT;
}

// The loop function is called in an endless loop
void loop()
{
switch( deviceState )
{
case DEVICE_STATE_INIT:
{
#if(LORAWAN_DEVEUI_AUTO)
LoRaWAN.generateDeveuiByChipID();
#endif
LoRaWAN.init(loraWanClass,loraWanRegion);
break;
}
case DEVICE_STATE_JOIN:
{
LoRaWAN.join();
break;
}
case DEVICE_STATE_SEND:
{
prepareTxFrame( appPort );
LoRaWAN.send(loraWanClass);
deviceState = DEVICE_STATE_CYCLE;
break;
}
case DEVICE_STATE_CYCLE:
{
// Schedule next packet transmission
txDutyCycleTime = appTxDutyCycle + randr( -APP_TX_DUTYCYCLE_RND, APP_TX_DUTYCYCLE_RND );
LoRaWAN.cycle(txDutyCycleTime);
deviceState = DEVICE_STATE_SLEEP;
break;
}
case DEVICE_STATE_SLEEP:
{
LoRaWAN.sleep(loraWanClass,debugLevel);
break;
}
default:
{
deviceState = DEVICE_STATE_INIT;
break;
}
}
}

You can refer to this example for rewriting.