MRF24J40 wireless module with LPCXpresso Base Board

This project demonstrates how easy it is to communicate between two MRF24J40 modules using LPC1343 LPCXpresso and Embedded Artists LPCXpresso Base board.


MRF24J40 module
Figure 1 - MRF24J40 module

 

Required Parts

Preparation

Connect the MRF24J40 module to the LPCXpresso Base Board according to the PIN configuration below.

  • SDI is connected to GPIO0.9
  • SDO is connected to GPIO0.8
  • SCK is connected to GPIO2.11
  • CS is connected to GPIO1.11
  • RESET is connected to GPIO0.0
  • WAKE is connected to GPIO2.8
  • INT is connected to GPIO2.9

MRF24J40 Connected to Base board
Figure 2 - MRF24J40 Connected to the Base board

Description

To initialize the RF module we did as suggested in the datasheet for MRF24J40 and also before data packets can be transmitted or received the TXNIF and RXIF interrupts must be enabled.

	// Place the device in hardware reset
	GPIOSetValue(PORT0, 0, 1);
	delay32Ms(0, 300);

	// Remove the device from hardware reset
	GPIOSetValue(PORT0, 0, 1);
	delay32Ms(0, 300);

	// Pin setup for CS, WAKE and INT
	pinSetup();

	// Reset the RF module
	setShortRAMAddr(WRITE_RFCTL, 0x01);
	// Remove the RF module from reset
	setShortRAMAddr(WRITE_RFCTL,0x00);


	// Flush the RX fifo
	setShortRAMAddr(WRITE_RXFLUSH,0x01);
	// Program the short MAC Address, 0xffff
	setShortRAMAddr(WRITE_SADRL,0xFF);
	setShortRAMAddr(WRITE_SADRH,0xFF);
	setShortRAMAddr(WRITE_PANIDL,0xFF);
	setShortRAMAddr(WRITE_PANIDH,0xFF);


	// Program Long MAC Address
	for (i = 0; i < 8; i++) {
	  setShortRAMAddr(WRITE_EADR0 + i * 2, myLongAddress[i]);
	}

	// Enable the RF-PLL
	setLongRAMAddr(RFCON2, 0x80);
	// Set TX for max output power
	setLongRAMAddr(RFCON3,0x00);
	// Enabled TX filter control
	setLongRAMAddr(RFCON6,0x80);
	setLongRAMAddr(RFCON8,0b00010000);
	// Program CCA mode using RSSI
	setShortRAMAddr(WRITE_BBREG2,0x78);
	// Enable the packet RSSI
	setShortRAMAddr(WRITE_BBREG6,0x40);
	// Program CCA, RSSI threshold values
	setShortRAMAddr(RSSITHCCA,0x00);

	//Enable only TXNIF and RXIF interrupts
	setShortRAMAddr(WRITE_INTCON, 0xF6);

	// Set channel
	setLongRAMAddr(RFCON0,CHANNEL_11);
	//Reset the RF module with new settings
	setShortRAMAddr(WRITE_RFCTL,0x04);
	setShortRAMAddr(WRITE_RFCTL,0x00);

The MRF24J40 supports IEEE 802.15.4 standard so that's what's used in this example application for the data packet format. The table below shows the structure of a packet for transmits.

Address Memory Length Description
0x00 Header length 1 byte Length of the security Header
0x01 Packet length 1 byte Length of the packet, not including the length or FCS
0x02 Frame Control 2 bytes Frame control describes how this packet should behave
0x04 Sequence Number 1 byte Sequence number of the packet
0x05 Data Length of data Destination and source addressing information and application data if any
0x06+Length of data FCS 2 bytes Packet CRC value, added by hardware

Table 1 - Transmit Packet format

Example code on how to setup a data packet.

Note: In this example application no security is implemented so the security header length is set to zero. In the frame control it is specified that both the short address for destination and the short address of the source is added.

  setLongRAMAddr(0x000, 0x00); //Security header length
  setLongRAMAddr(0x001, (size - 1)); //Length
  setLongRAMAddr(0x002, 0x01); //Frame control, Data command
  setLongRAMAddr(0x003, 0x88); //Frame control, short destination 
                               //address + short source address
  setLongRAMAddr(0x004, sequenceID); //Sequence id

  setLongRAMAddr(0x005, 0xFF); //Destination address, PANID_LSB
  setLongRAMAddr(0x006, 0xFF); //PANID_MSB
  setLongRAMAddr(0x007, 0xAA); //Destination address LSB
  setLongRAMAddr(0x008, 0xAA); //Destination address MSB

  setLongRAMAddr(0x009, 0xFF); //Source address, PANID_LSB
  setLongRAMAddr(0x00A, 0xFF); //PANID_MSB
  setLongRAMAddr(0x00B, 0xBB); //Source address LSB
  setLongRAMAddr(0x00C, 0xBB); //Source address MSB

  index = 0;

  for (i = 0x00D; i <= size; i++) {
     setLongRAMAddr(i, buf[index]); //Data
     ++index;
  }
  
  setShortRAMAddr(WRITE_TXNCON, 0x01); //Transmit packet without 
                                       //ACK requested

And the receive packet is structured as the table below.

Address Memory Length Description
0x300 Packet length 1 byte Length of the packet, not including the length or FCS
0x301 Frame Control 2 bytes Frame control describes how this packet should behave
0x303 Sequence Number 1 byte Sequence number of the packet
0x304 Data Length of data Destination and source addressing information and application data if any
0x305+Length of data FCS 2 bytes The CRC value of the packet. The RX buffer is cleared when the length byte of the packet and the last byte of the FCS are read. Once both of these values are read from the RX buffer, the buffer will enable itself to receive another packet. So it could be a good practice to read FCS last.
0x307+Length of data LQI 1 byte Link quality index of the packet
0x308+Length of data RSSI 1 byte Received signal strength indicator for the received packet

Table 2 - Receive Packet format

In main() the GPIO interrupt handler must be installed and timers initiated to use delays. It is also needed to initialize the SSP port routine and setup the UART to 115200 baud rate. After that the MRF24J40 module is initialized, print the menu to the terminal and handle the menu options.

This small example application demonstrates how to send and receive packets with the MRF24J40 module

int main(void) {
   init_timer32(0, 10);
   GPIOInit();
   SSPInit();
   UARTInit(115200);
   initMRF24J40();

   while (1) {
      printMenu();
      handleCommand();
      delay32Ms(0, 100);
   }

   return 1;
}

Usage of example in two terminal applications
Figure 3 - Usage shown in two terminal applications

Source code

Import project into LPCXpresso IDE

Begin by importing the driver and sample application bundle (zip file) for the LPC1343 LPCXpresso Board found at the Embedded Artists support site.

  1. In the LPCXpresso IDE, Quickstart tab, choose Import Example project(s)
  2. Browse to the downloaded zip file (for example lpc1343_xpr_bb_100222.zip)
  3. Click finish to import the drivers and sample applications.

The second step is to import the MRF24J40 module project. Do the same as when importing the drivers, but choose MRF24J40_example.zip in step 2. To build or debug the example just click build/debug in the QuickStart tab

More information on how to work with the LPCXpresso Base Board as well as the LPCXpresso IDE can be found in the User's Manual for the LPCXpresso Base Board. This User's Manual can be found at the Embedded Artists support site.