ReferenceComLayer

MANTIS COM Layer

The COM Layer is used to interface with communication devices, such as the CC2420 or CC1000 radio, as well as the serial ports. The interface is as follows:

com_mode(IFACE, uint8_t mode)

Change the mode of the specified interface.

com_send(IFACE, comBuf* buffer)

Sends data to the specified interface.

comBuf* com_recv(IFACE)

Receives data from the specified interface.

void com_free_buf(comBuf* buffer)

Releases a buffer returned from com_recv back to the system for reuse. It is important to call this when you are done with a comBuf, or the system might run out of free buffers.

COM Buffers

COM Buffers (comBuf) are structures used when sending and receiving from a com layer device. The COM Buffer has the following useful members:

uint8_t data[COM_DATA_SIZE]
uint8_t size

the data byte array is the actual data that the comBuf is carrying. size indicates the number of bytes in the data array. COM_DATA_SIZE is the maximum number of bytes that can be carried in a single comBuf.

Interfaces

The most commonly used interfaces are IFACE_RADIO and IFACE_SERIAL, which allow access to the radio (cc2420 or cc1000) and the terminal respectively. On TelosB nodes, IFACE_SERIAL2 is used to interact with the terminal.

Example

The following example application is a simple echo program, which will receive a packet over the radio and echo it back:

#include "mos.h"
#include "com.h"
#include "printf.h"

void echo_thread(void)
{
   com_mode(IFACE_RADIO, IF_LISTEN);
   
   while(1)
   {
      comBuf* p = com_recv(IFACE_RADIO);
      
      com_send(IFACE_RADIO, p);
      printf("echoed %d bytes\n", p->size);
      // release the comBuf back to the OS.
      com_free_buf(p);
   }
}

void start(void)
{
   mos_thread_new(echo_thread, 128, PRIORITY_NORMAL);
}

Created by: ledbettj last modification: Wednesday 01 of August, 2007 [19:50:46 UTC] by ledbettj

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