myapp_ex02.c

This network protcol stack,it is very strong and powerful!

/******************************************************************************
*   MyApp_Ex01.c  - Initialization and main loop. 
* = MyApp_Ex02.c  - Energy Detection Scan.======================== This file == 
*   MyApp_Ex03a.c - A PAN Coordinator is started
*   MyApp_Ex03b.c - Device locates coordinator using Active Scan
*   MyApp_Ex04a.c - Coordinator responds to an Associate request
*   MyApp_Ex04b.c - Device Associates to the PAN coordinator
*   MyApp_Ex05a.c - Coordinator receives data from device
*   MyApp_Ex05b.c - Device sends direct data to the coordinator
*   MyApp_Ex06a.c - Coordinator sends indirect data to device
*   MyApp_Ex06b.c - Device polls for data from the coordinator
*   MyApp_Ex07a.c - Coordinator starts a beaconed network
*   MyApp_Ex07b.c - Device receives data using automatic polling
*   MyApp_Ex08a.c - Coordinator uses security
*   MyApp_Ex08b.c - Device uses security
*
* This demo application builds on MyApp_Ex01.c. The primary purpose of this
* application is to demonstrate how to use the Energy Detection Scan feature
* of the MAC. 
* 
* The Energy Detection Scan is used for scanning a range of channels in order
* to select a specific channel to operate a PAN on. The criteria for selecting
* a channel is that it has a very low energy level. Thus, the probability of
* interfering with other 2.4GHz transmitters (802.15.4, WLAN, microwave oven,
* etc.) is minimized.
* 
* The steps required the do an Energy Detection Scan are:
* 1) Build and send a MLME-Scan Request message to the MAC.
* 2) Wait for the MLME-Scan Confirm message from the MAC.
* 3) Use the energy detect information in the confirm message for selecting
*    the channel with least energy. The selected channel is stored in a
*    global variable for later use.
*
* Step 1 is performed by the 'stateScanEdStart' state, and steps 2 to 3 are 
* performed by the 'stateScanEdWaitConfirm' state.
*
******************************************************************************/

#include "802_15_4.h" /* Include everything related to the 802.15.4 interface*/
#include "Uart.h"     /* Defines the interface of the demo UART. */

/* Defines the channels to scan. Each bit represents one channel. Use
   0x07FFF800 to scan all 16 802.15.4 channels in the 2.4GHz band. */
#define SCAN_CHANNELS 0x07FFF800

/* Forward declarations of helper functions */
uint8_t App_StartScan(uint8_t scanType);
void    App_HandleScanEdConfirm(nwkMessage_t *pMsg);
uint8_t App_WaitMsg(nwkMessage_t *pMsg, uint8_t msgType);


/* The various states of the application state machine. */
enum {
  stateInit,
  stateScanEdStart,
  stateScanEdWaitConfirm,
  stateListen,
  stateTerminate
};

/* Error codes */
enum {
  errorNoError,
  errorWrongConfirm,
  errorNotSuccessful,
  errorNoMessage,
  errorAllocFailed,
  errorInvalidParameter,
  errorNoScanResults
};


/* The current state of the applications state machine */
uint8_t state;

/* The status parameter of the latest confirm message from the MLME */
uint8_t confirmStatus;

/* The current logical channel (frequency band) */
uint8_t logicalChannel;

/* Application input queues */
anchor_t mMlmeNwkInputQueue;

/* Application Main Loop */
void main(void)
{ 
  /* Pointer for storing the messages from MLME */
  void *pMsgIn;
  /* Stores the error/success code returned by some functions. */
  uint8_t ret;
  /* return value of Mlme_Main() - not used yet */
  uint8_t macStatus;
  
  /* Initialize variables */
  state = stateInit;

  /* Prepare input queues.*/
  MSG_InitQueue(&mMlmeNwkInputQueue);
  
  /* Execute the application state machine */    
  while(state < stateTerminate)
  {
    /* Preset return code to contain the success code */
    ret = errorNoError;
    
    /* Try to get a message from MLME */
    if(MSG_Pending(&mMlmeNwkInputQueue))
      pMsgIn = MSG_DeQueue(&mMlmeNwkInputQueue);
    else
      pMsgIn = NULL;
      
    switch(state)
    {
    case stateInit:
      /* Initialize the UART so that we can print out status messages */
      Uart_Init();
      /* Initialize the 802.15.4 stack */
      Init_802_15_4();
      /* Goto Energy Detection state. */
      state = stateScanEdStart;

      /* Print a welcome message to the UART */
      Uart_Print("The Myapp_Ex02 demo application is initialized and ready.\n\n");
      break;
      
    case stateScanEdStart:
      /* Start the Energy Detection scan, and goto wait for confirm state. */
      Uart_Print("Initiating the Energy Detection Scan\n");
      ret = App_StartScan(gScanModeED_c);
      if(ret == errorNoError)
      {
        state = stateScanEdWaitConfirm;
      }
      break;
      
    case stateScanEdWaitConfirm:
      /* Stay in this state until the MLME Scan confirm message
         arrives, and has been processed. Then goto listen state. */
      ret = App_WaitMsg(pMsgIn, gNwkScanCnf_c);
      if(ret == errorNoError)
      {
        /* Process the ED scan confirm. The logical
           channel is selected by this function. */
        App_HandleScanEdConfirm(pMsgIn);
        state = stateListen;
      }
      break;
      
    case stateListen:
      /* Stay in this state forever. */
      break;
    }
    
    if(pMsgIn)
    {
      /* Messages from the MLME must always be freed. */
      MSG_Free(pMsgIn);
    }
    
    /* Call the MAC main function continuously. */
    macStatus = Mlme_Main();
  }
}


/******************************************************************************
* The App_StartScan(scanType) function will start the scan process of the
* specified type in the MAC. This is accomplished by allocating a MAC message,
* which is then assigned the desired scan parameters and sent to the MLME
* service access point.
* The function may return either of the following values:
*   errorNoError:          The Scan message was sent successfully.
*   errorInvalidParameter: The MLME service access point rejected the
*                          message due to an invalid parameter.
*   errorAllocFailed:      A message buffer could not be allocated.
*
******************************************************************************/
uint8_t App_StartScan(uint8_t scanType)
{
  mlmeMessage_t *pMsg;
  mlmeScanReq_t *pScanReq;

  Uart_Print("Sending the MLME-Scan Request message to the MAC...");

  /* Allocate a message for the MLME (We should check for NULL). */
  pMsg = MSG_AllocType(mlmeMessage_t);
  if(pMsg != NULL)
  {
    /* This is a MLME-START.req command */
    pMsg->msgType = gMlmeScanReq_c;
    /* Create the Start request message data. */
    pScanReq = &pMsg->msgData.scanReq;
    /* gScanModeED_c, gScanModeActive_c, gScanModePassive_c, or gScanModeOrphan_c */
    pScanReq->scanType = scanType;
    /* ChannelsToScan & 0xFF - LSB, always 0x00 */
    pScanReq->scanChannels[0] = (uint8_t)((SCAN_CHANNELS)     & 0xFF);
    /* ChannelsToScan>>8 & 0xFF  */
    pScanReq->scanChannels[1] = (uint8_t)((SCAN_CHANNELS>>8)  & 0xFF);
    /* ChannelsToScan>>16 & 0xFF  */
    pScanReq->scanChannels[2] = (uint8_t)((SCAN_CHANNELS>>16) & 0xFF);
    /* ChannelsToScan>>24 & 0xFF - MSB */
    pScanReq->scanChannels[3] = (uint8_t)((SCAN_CHANNELS>>24) & 0xFF);
    /* Duration per channel 0-14 (dc). T[sec] = (16*960*((2^dc)+1))/1000000.
       A scan duration of 5 on 16 channels approximately takes 8 secs. */
    pScanReq->scanDuration = 5;
    
    /* Send the Scan request to the MLME. */
    if(MSG_Send(NWK_MLME, pMsg) == gSuccess_c)
    {
      Uart_Print("Done\n");
      return errorNoError;
    }
    else
    {
      Uart_Print("Invalid parameter!\n");
      return errorInvalidParameter;
    }
  }
  else
  {
    /* Allocation of a message buffer failed. */
    Uart_Print("Message allocation failed!\n");
    return errorAllocFailed;
  }
}


/******************************************************************************
* The App_HandleScanEdConfirm(nwkMessage_t *pMsg) function will handle the
* ED scan confirm message received from the MLME when the ED scan has completed.
* The message contains the ED scan result list. This function will search the
* list in order to select the logical channel with the least energy. The
* selected channel is stored in the global variable called 'logicalChannel'.
*
******************************************************************************/
void App_HandleScanEdConfirm(nwkMessage_t *pMsg)
{  
  uint8_t n, minEnergy;
  uint8_t *pEdList;

  Uart_Print("Recevied the MLME-Scan Confirm message from the MAC\n");
    
  /* Get a pointer to the energy detect results */
  pEdList = pMsg->msgData.scanCnf.resList.pEnergyDetectList;
  
  /* Set the minimum energy to a large value */
  minEnergy = 0xFF;

  /* Select default channel */
  logicalChannel = 11;
 
  /* Search for the channel with least energy */
  for(n=0; n<16; n++)
  {
    if(pEdList[n] < minEnergy)
    {
      minEnergy = pEdList[n];
      /* Channel numbering is 11 to 26 both inclusive */
      logicalChannel = n + 11; 
    }
  }
  
  /* Print out the result of the ED scan */
  Uart_Print("ED scan returned the following results:\n  [");
  Uart_PrintHex(pEdList, 16, gPrtHexBigEndian_c | gPrtHexCommas_c);
  Uart_Print("]\n\n");
  
  /* Print out the selected logical channel */
  Uart_Print("Based on the ED scan the logical channel 0x");
  Uart_PrintHex(&logicalChannel, 1, 0);
  Uart_Print(" was selected\n");
  
  /* The list of detected energies must be freed. */
  MSG_Free(pEdList);
}


/******************************************************************************
* The App_WaitMsg(nwkMessage_t *pMsg, uint8_t msgType) function does not, as
* the name implies, wait for a message, thus blocking the execution of the
* state machine. Instead the function analyzes the supplied message to determine
* whether or not the message is of the expected type.
* The function may return either of the following values:
*   errorNoError: The message was of the expected type.
*   errorNoMessage: The message pointer is NULL.
*   errorWrongConfirm: The message is not of the expected type.
*
******************************************************************************/
uint8_t App_WaitMsg(nwkMessage_t *pMsg, uint8_t msgType)
{
  /* Do we have a message? If not, the exit with error code */
  if(pMsg == NULL)
    return errorNoMessage;

  /* Is it the expected message type? If not then exit with error code */
  if(pMsg->msgType != msgType)
    return errorWrongConfirm;

  /* Found the expected message. Return with success code */
  return errorNoError;
}


/******************************************************************************
* The following functions are called by the MAC to put messages into the
* Application's queue. They need to be defined even if they are not used
* in order to avoid linker errors.
******************************************************************************/

uint8_t MLME_NWK_SapHandler(nwkMessage_t * pMsg)
{
  /* Put the incoming MLME message in the applications input queue. */
  MSG_Queue(&mMlmeNwkInputQueue, pMsg);
  return gSuccess_c;
}

uint8_t MCPS_NWK_SapHandler(mcpsToNwkMessage_t *pMsg)
{
  /* If the message is not handled anywhere it must be freed. */
  MSG_Free(pMsg);
  return gSuccess_c;
}

uint8_t ASP_APP_SapHandler(aspToAppMsg_t *pMsg)
{
  /* If the message is not handled anywhere it must be freed. */
  MSG_Free(pMsg);
  return gSuccess_c;
}