Difference between revisions of "PIC32MX: XBee Wireless Round-trip Latency"

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Line 106: Line 106:
mLED_2_On();
mLED_2_On();
mLED_3_On();
mLED_3_On();
PIN_D1 = 1; // Set the pin high to begin the clocking
PIN_D1 = 1; // Set the pin high to begin the clocking
putsUART2("1234.\r\n"); // This is where the message goes. Note the period at the end of the message
putsUART2("1234.\r\n"); // This is where the message goes. Note the period at the end of the message
break; // Code only sends the stuff in UART2 ONE time.
break; // Code only sends the stuff in UART2 ONE time.

Revision as of 17:20, 13 February 2010

Original Assignment

Do not erase this section!

Your assignment is to set up one PIC32 to send data to another using XBees for wireless RS-232 comm. One PIC will send a series of numbers; the other PIC will receive them and echo them back; and the first PIC will time the total time to send and receive back. To time, the first PIC can set a digital pin high, then set it low again when the original sent data is correctly received. It could also keep track of the count of a counter-timer. You can time how long it takes for the round-trip using an oscilloscope or by reading the counter-timer. You should try this for different baud rates and a couple of different sizes (in bytes) of the message. How low can you get the total round-trip time while guaranteeing low data loss?

Overview

Summarize briefly what the page is about.

Circuit

Include a schematic and give any part numbers. A photo of your circuit is OK, but not as a replacement for a schematic.

Code

The code below is for the transmitter XBee chip. Note that the message string sent included only one period and was placed at the end. The program scans the message it receives looking for that period, so it knows that the whole message was received.

/********************************************************************** 

     Transmitter Code
     Lab 5: High Speed XBee Latency
     George Randolph
     Nathan Hirsch
     10 February 2010

This code is for the TRANSMITTER XBee chip.  It takes a string of characters and 
sends them from the PIC to the XBee and broadcasts it out into the world.  The 
reciever chip should receive the message and echo it back to the transmitter.  At
the point when the transmitter first broadcasts the message, a pin on the PIC is 
set to high.  When the message is successfully echoed back, that pin is set low 
so the whole process can be timed using an oscilloscope.

**********************************************************************/


// ****** Includes 
#include "HardwareProfile.h"

// ****** Constants
#define DESIRED_BAUDRATE    	(115200)	      // The desired BaudRate Note: This must be changed when changing the XBee chip BaudRate
#define PIN_D1			LATDbits.LATD1
#define PIN_D2			LATDbits.LATD2
#define PIN_D3			LATDbits.LATD3
#define PIN_D4			LATDbits.LATD4

// ****** Variables
unsigned int Time;
char RS232_Out_Buffer[64];  			      // The buffer may be changed if lots of data is being sent at a high BaudRate
char message;


// ****** Function Declarations
void initInterruptController();

// ****** Main Function
int main(void)
{
	int	pbClk;
	//initUART2(pbClk);
	
	// Configure the system performance
	pbClk = SYSTEMConfigPerformance(SYS_FREQ); 
	
	mInitAllLEDs();
		
		// define setup Configuration 2 for OpenUARTx
		// IrDA encoded UxTX idle state is '0'
		// Enable UxRX pin
		// Enable UxTX pin
		// Interrupt on transfer of every character to TSR 
		// Interrupt on every char received
		// Disable 9-bit address detect
		// Rx Buffer Over run status bit clear
	#define config2		UART_TX_PIN_LOW | UART_RX_ENABLE | UART_TX_ENABLE | UART_INT_TX | UART_INT_RX_CHAR | UART_ADR_DETECT_DIS | UART_RX_OVERRUN_CLEAR
	
	// Open UART2 with config1 and config2
	OpenUART2(config1, config2, pbClk/16/DESIRED_BAUDRATE-1);	// calculate actual BAUD generate value.

	// Configure UART2 RX Interrupt with priority 7
	ConfigIntUART2(UART_INT_PR7 | UART_RX_INT_EN);

	// Must enable glocal interrupts - in this case, we are using multi-vector mode
        INTEnableSystemMultiVectoredInt();
 	
	//Set D1, D2, D3, and D4 as a digital output
	LATD |= 0x001E; TRISD &= 0xFFE1;


	while(1) //let interrupt handle the UART
	{ 
		if (swUser) // swUser NOT pressed
		{
		// Turn off all the lights to show that the message has not been sent 
		mLED_0_Off();
		mLED_1_Off();
		mLED_2_Off();
		mLED_3_Off();
		PIN_D1 = 0;
		}
		else
		{
		// Turn on all the lights to show that the message was sent	
		mLED_0_On();
		mLED_1_On();
		mLED_2_On();
		mLED_3_On();
       	PIN_D1 = 1; 			    // Set the pin high to begin the clocking 
		putsUART2("1234.\r\n");     // This is where the message goes.  Note the period at the end of the message
		break; 			    // Code only sends the stuff in UART2 ONE time.  
		}
		
	}
   return 0;
}