PIC32MX: XBee Wireless Round-trip Latency - Revision history

NathanHirsch: /* Notes */

2010-03-16T23:07:34Z

Notes

NickMarchuk at 20:19, 1 March 2010

2010-03-01T20:19:53Z

HenryRandolph: /* Circuit */

2010-02-15T21:02:41Z

Circuit

HenryRandolph: /* Circuit */

2010-02-15T21:01:42Z

Circuit

NathanHirsch: /* Transmitter Code */

2010-02-15T20:59:13Z

Transmitter Code

NathanHirsch: /* Transmitter Code */

2010-02-15T20:58:31Z

Transmitter Code

NathanHirsch: /* Overview */

2010-02-15T20:53:08Z

Overview

NathanHirsch: /* Overview */

2010-02-15T20:52:26Z

Overview

NathanHirsch: /* Overview */

2010-02-15T20:52:11Z

Overview

HenryRandolph: /* Receiver Code */

2010-02-15T20:51:46Z

Receiver Code

@@ Line 265: / Line 265: @@
 ==Notes==
 The message string that was sent ended in a period and there was only one period in the whole message string.  We used this to assure that the entire string was read before assigning the digital pin that clocked the entire transfer process to low.
+[[Remote Controlled Guitar]]
 ==Results==

@@ Line 1: / Line 1: @@
-== Original Assignment ==
-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 ==
 [[Image:George Randolph.jpg|thumb|200px|George Randolph|right]]

@@ Line 39: / Line 39: @@
 [[Image:Xbee_board_with_radio.jpg|thumb|150px|XBee chip|right]]
 The pinout of the XBee chip can be seen in the image to the right.  Note the RTS and CTS pins on the XBees were not used during the experiment.
-Notice how the XBee chip is constructed so that it can be stuck into a solderless protoboard or plugged directly into a [[PIC32MX:_RS232 | RS232]] cable.  We were using the standard version of Digi's XBee chip, but they sell a "pro" version which they claim works up to a mile away.  The advantage to this is that both the pro and consumer versions of these chips have the same pin-outs and they are interchangeable.  That is, the XBee chips are removable from the [[XBee Interface Board]] and the pro and standard versions can both be used.
+Notice how the XBee chip is constructed so that it can be stuck into a solderless protoboard or plugged directly into a [[PIC32MX:_RS232 | RS232]] cable.  We were using the standard version of Digi's XBee chip, but they sell a "pro" version which they claim works up to a mile away.  The advantage to this is that both the pro and consumer versions of these chips have the same pin-outs and they are interchangeable.  That is, the XBee chips are removable from the [[XBee Interface Board]] wherein the pro and standard versions can be used.

@@ Line 39: / Line 39: @@
 [[Image:Xbee_board_with_radio.jpg|thumb|150px|XBee chip|right]]
 The pinout of the XBee chip can be seen in the image to the right.  Note the RTS and CTS pins on the XBees were not used during the experiment.
-Notice how the XBee chip is constructed so that it can be stuck into a solderless protoboard or plugged directly into a [[PIC32MX:_RS232 | RS232]] cable.  We were using the standard version of Digi's XBee chip, but they sell a "pro" version which they claim works up to a mile away.  These chips are obviously more expensive. ''--probably don't need this line.  talk about how pro and regular are interchangeable.''
+Notice how the XBee chip is constructed so that it can be stuck into a solderless protoboard or plugged directly into a [[PIC32MX:_RS232 | RS232]] cable.  We were using the standard version of Digi's XBee chip, but they sell a "pro" version which they claim works up to a mile away.  The advantage to this is that both the pro and consumer versions of these chips have the same pin-outs and they are interchangeable.  That is, the XBee chips are removable from the [[XBee Interface Board]] and the pro and standard versions can both be used.
 <br clear=all>
 ===X-CTU===

@@ Line 124: / Line 124: @@
  	#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
   	#define config1 UART_EN | UART_IDLE_CON | UART_RX_TX | UART_DIS_WAKE | UART_DIS_LOOPBACK | UART_DIS_ABAUD | UART_NO_PAR_8BIT | UART_1STOPBIT | UART_IRDA_DIS |
                          UART_DIS_BCLK_CTS_RTS| UART_NORMAL_RX | UART_BRGH_SIXTEEN
  	// Open UART2 with config1 and config2
  	OpenUART2(config1, config2, pbClk/16/DESIRED_BAUDRATE-1);	// calculate actual BAUD generate value.

@@ Line 90: / Line 90: @@
  #define PIN_D1			LATDbits.LATD1        // These commands format pins D1-D4 as digital outputs.
  #define PIN_D2			LATDbits.LATD2        // Note we used D1, but you may find it necessary to use different output pins.
- #define PIN_D3			LATDbits.LATD3       // This code sets up 4 potential digital outputs.
+ #define PIN_D3			LATDbits.LATD3        // This code sets up 4 potential digital outputs.
  #define PIN_D4			LATDbits.LATD4

← Older revision		Revision as of 20:53, 15 February 2010
Line 6:		Line 6:
	[[Image:George Randolph.jpg\|thumb\|200px\|George Randolph\|right]]		[[Image:George Randolph.jpg\|thumb\|200px\|George Randolph\|right]]
	It is often useful to send signals from one PIC to another wirelessly. One way to achieve this is to use XBee communication. XBee chips use radio frequency waves to send wireless signals. These chips can basically replace other, wired forms of communication like RS232.		It is often useful to send signals from one PIC to another wirelessly. One way to achieve this is to use XBee communication. XBee chips use radio frequency waves to send wireless signals. These chips can basically replace other, wired forms of communication like RS232.

@@ Line 6: / Line 6: @@
 [[Image:George Randolph.jpg|thumb|200px|George Randolph|right]]
 It is often useful to send signals from one PIC to another wirelessly.  One way to achieve this is to use XBee communication.  XBee chips use radio frequency waves to send wireless signals.  These chips can basically replace other, wired forms of communication like RS232.
 There are obvious advantages to using wireless communication, but there are also disadvantages.  One disadvantage is that wireless communication is generally slower than wired communication.  In this lab, we will record the time it takes for a signal to be sent from one PIC to another and back again.
@@ Line 14: / Line 17: @@
 [[Image:Nathan Hirsch.Team15.2010.jpeg|thumb|200px|Nathan Hirsch|right]]
 To accomplish this, we have written code for two PICs which control two XBee chips.  One PIC-Xbee combination is responsible for sending a signal and recording the time it takes for that signal to come back to it.  The second PIC-XBee combination recieves the signal from the first PIC and echos it back.  To time the process, the first PIC sets a digital output from low to high just before sending out its signal.  When the last character of the signal is recieved back, the PIC sets the output pin low.  This low-high-low pulse is observed and timed using an oscilloscope.
 Several factors can affect the speed at which the process happens. For one thing, XBee chips are able to communicate using various baud rates (the rate, in bits per second, signals are sent and recieved).  Another factor that can affect the speed of wireless communication between two PICs is the size of the message being sent.  To see how each of these changed the communication time, we ran two experiments.  First, we varied the baud rate of the system while holding the size of the message constant.  Then we varied the size of the message while holding the baud rate at a maximum.  A third experiment was developed to see if the distance between the two communicating XBee chips would affect the latency time, but no changes were observed within the confines of the Mechatronics lab.

@@ Line 199: / Line 199: @@
  	Nathan Hirsch
 February 2010
+  This is the RECEIVER code.  It takes the message sent by the transmitter and then echoes it back.
+  When the whole message is sent, all the LEDs on the receiver board turn on.  When the receiver
+  gets some data, only 2/4 LEDs turn on, signaling that some information was received and sent
+  back, just not the correct data.  This is just used for visual feedback for the user.
  ***************************************************/