C/ C++ code snippet needed: Unwrap MAC commands from payload KI

Verkehrsrot · August 31, 2019, 4:40pm

I want to enhance my paxcounter software with a simple MAC command display, to show MAC commands received by the network.

For this purpose i’m looking for a c/c++ code snippet, which unwraps MAC commands from a (already decrypted bei LMiC) Lmic.frame.

Any hints?

github.com

cyberman54/ESP32-Paxcounter/blob/development/src/lorawan.cpp#L605




// transmit complete message handler

void myTxCallback(void *pUserData, int fSuccess) {



  /* currently no code here */



  // tell the compiler that pUserData is required by the API, but we don't

  // happen to use it.

  LMIC_API_PARAMETER(pUserData);

}



// LORAWAN MAC interpreter



// table of LORAWAN MAC messages sent by the network to the device

// format: opcode, cmdname (max 19 chars), #bytes params

// source: LoRaWAN 1.1 Specification (October 11, 2017)



static mac_t table[] = {

    {0x01, "ResetConf", 1},          {0x02, "LinkCheckAns", 2},

    {0x03, "LinkADRReq", 4},         {0x04, "DutyCycleReq", 1},

    {0x05, "RXParamSetupReq", 4},    {0x06, "DevStatusReq", 0},

cjhdev · August 31, 2019, 5:08pm

Isn’t it already implemented in mac_decode()?

If you want an implementation that unpacks the fields into a structure you can use this one.

Verkehrsrot · August 31, 2019, 5:46pm

I think i need to unwrap the MAC command from the frame structure (FHDR etc.), this part is still missing.

Verkehrsrot · August 31, 2019, 6:53pm

My problem is here, where calling the decoder with the unwrapped frame:

github.com

cyberman54/ESP32-Paxcounter/blob/development/src/lorawan.cpp#L567




// list MAC messages, if any

uint8_t nMac = pMsg - &LMIC.frame[0];

if (port != MACPORT)

  --nMac;

if (nMac) {

  ESP_LOGI(TAG, "Received %u MAC messages:", nMac);

  // NOT WORKING YET

  // whe need to strip some protocol overhead from LMIC.frame to unwrap the

  // MAC command

  mac_decode(LMIC.frame, nMac);

}



switch (port) {



  // ignore mac messages

case MACPORT:

  break;



// rcommand received -> call interpreter

case RCMDPORT: