IR communication between PICs - Revision history

Victor Liu: /* Circuit */

2009-02-12T18:19:54Z

Circuit

Victor Liu: /* Circuit */

2009-02-12T18:19:26Z

Circuit

Victor Liu: /* Limitations */

2009-02-12T18:12:46Z

Limitations

Victor Liu: /* Circuit */

2009-02-12T02:58:26Z

Circuit

Victor Liu: /* Circuit */

2009-02-12T02:55:16Z

Circuit

Victor Liu: /* Circuit */

2009-02-12T02:52:23Z

Circuit

Victor Liu: /* Overview */

2009-02-12T02:51:22Z

Overview

Victor Liu at 02:48, 12 February 2009

2009-02-12T02:48:55Z

Victor Liu: /* Circuit */

2009-02-12T02:46:21Z

Circuit

Victor Liu at 02:45, 12 February 2009

2009-02-12T02:45:31Z

@@ Line 23: / Line 23: @@
 <!--[[Image:Serial_ir_data_format.jpg|right|thumb|400px|Serial & IR Data Format]]-->
+[[Image:ir_connect.jpg|right|thumb|400px|Source PIC Transmitting to the Receiver PIC]]
 ===IR Interface===
@@ Line 29: / Line 30: @@
 ===Optical Interface===
 The optical interface refers to the actual IR energy being transmitted between two transceivers or a source and a receiver.  The optical signal is a modulated form of the signal between the Endec and the Transceiver at the Transceiver's carrier frequency, 38 kHz.  That means that when the Endec would transmit a pulse for 3 cycles at the 16XCLK frequency, the transceiver would start pulsing IR energy at 38 kHz until the pulse went low.  When the transceiver receive IR pulsed at 38 kHz, the duration of the IR pulses is the duration of the pulse sent to the Endec.
-[[Image:ir_connect.jpg|right|thumb|400px|Source PIC Transmitting to the Receiver PIC]]
 ===Electrical Characteristics===

@@ Line 22: / Line 22: @@
 There is also a 16XCLK signal going to the endec from the PIC used to control the baud rate of the endec; that signal is a square wave pulse train at a frequency of 16*(the baud rate) and is generated in software. The <span style="text-decoration: overline">RESET</span> signal on the endec could be controlled with software but is simply held high since the endec need not be reset.
-[[Image:Serial_ir_data_format.jpg|right|thumb|400px|Serial & IR Data Format]]
+<!--[[Image:Serial_ir_data_format.jpg|right|thumb|400px|Serial & IR Data Format]]-->
 ===IR Interface===

@@ Line 56: / Line 56: @@
 *IR Communication is only Half-Duplex (only one transceiver transmitting at a time)
 *Transmission Distance maximum is about 12 feet (about 3ft in low power mode)
+*Transmission is easily blocked or reflected by obstacles
 *Communication Speed can only go up to 115.2 kpbs

@@ Line 15: / Line 15: @@
 [[Image:ir_source.jpg|thumb|right|400px|Actual Circuit (Receiver)]]
-The circuit diagram below shows a complete half-duplex IR communication circuit.  This circuit can either be used together with an identical circuit to communicate, with only one PIC transmitting at a time, or with a remote control.  The software on the PIC can be configured to respond to a variety of commands sent by the remote.  The electrical characteristics of the power supply and discrete components are given below.  Some of the ranges for the IR circuitry are also given below in parentheses.  In the circuit, there are two interfaces: the serial interface and the IR interface.
+The circuit diagram shows a complete half-duplex IR communication circuit.  This circuit can either be used together with an identical circuit to communicate, with only one PIC transmitting at a time, or with a remote control.  The software on the PIC can be configured to respond to a variety of commands sent by the remote.  The electrical characteristics of the power supply and discrete components are given below.  Some of the ranges for the IR circuitry are also given below in parentheses.  In the circuit, there are two interfaces: the serial interface and the IR interface.
 ===Serial Interface===

@@ Line 30: / Line 30: @@
 The optical interface refers to the actual IR energy being transmitted between two transceivers or a source and a receiver.  The optical signal is a modulated form of the signal between the Endec and the Transceiver at the Transceiver's carrier frequency, 38 kHz.  That means that when the Endec would transmit a pulse for 3 cycles at the 16XCLK frequency, the transceiver would start pulsing IR energy at 38 kHz until the pulse went low.  When the transceiver receive IR pulsed at 38 kHz, the duration of the IR pulses is the duration of the pulse sent to the Endec.
-[[Image:ir_connect.jpg|right|thumb|400px|IR Source & Receiver]]
+[[Image:ir_connect.jpg|right|thumb|400px|Source PIC Transmitting to the Receiver PIC]]
 ===Electrical Characteristics===

@@ Line 13: / Line 13: @@
 == Circuit ==
 [[Image:IR_circuit.jpg|thumb|right|400px|Circuit Diagram]]
-[[Image:ir_source.jpg|thumb|right|400px|Actual Circuit (Transmitter Source)]]
+[[Image:ir_source.jpg|thumb|right|400px|Actual Circuit (Receiver)]]
 The circuit diagram below shows a complete half-duplex IR communication circuit.  This circuit can either be used together with an identical circuit to communicate, with only one PIC transmitting at a time, or with a remote control.  The software on the PIC can be configured to respond to a variety of commands sent by the remote.  The electrical characteristics of the power supply and discrete components are given below.  Some of the ranges for the IR circuitry are also given below in parentheses.  In the circuit, there are two interfaces: the serial interface and the IR interface.

@@ Line 7: / Line 7: @@
 When transmitting, the PIC sends the serial format data to the endec, which encodes (or modulates) it bit by bit.  This encoded data is then outputted as electrical pulses to the transceiver.  The transceiver converts these electrical pulses to IR light pulses.  When receiving, the transceiver receives IR light pulses (data), which are outputted as electrical pulses. The endec decodes (or demodulates) these electrical pulses, with the data then being transmitted by the endec UART back to the receiving PIC. This modulation/demodulation method is performed in accordance with the IrDA standard.
-Both the PIC and the endec used in this example were DIP packages, making them easy to prototype and inspect.  The transceiver, however, was a surface mount chip with an uncommon pin configuration (0.95 mm pitch), requiring a different mounting approach.  The simplest solution was to glue the transceiver onto one side of a similar-sized socket, and then soldering small wires from the pins of the transceiver onto the pins of the socket (see image). In the previous years, other mounting methods were tried, including the use of a [http://www.radioshack.com/sm-2-sided-copper-clad-pc-board--pi-2102495.html copper-clad board] or a [http://www.schmartboard.com/index.asp?page=products_so&id=54 SchmartBoard]. However, these approaches saw limited success.
+Both the PIC and the endec used in this example were DIP packages, making them easy to prototype and inspect.  The transceiver, however, was a surface mount chip with an uncommon pin configuration (0.95 mm pitch), requiring a different mounting approach.  The simplest solution was to glue the transceiver onto one side of a 16 pin socket, and then soldering small wires from the 8 pins of the transceiver onto the pins of the socket (see image). In the previous years, other mounting methods were tried, including the use of a [http://www.radioshack.com/sm-2-sided-copper-clad-pc-board--pi-2102495.html copper-clad board] or a [http://www.schmartboard.com/index.asp?page=products_so&id=54 SchmartBoard]. However, these approaches saw limited success.
 <!--We initially attempted to etch a [http://www.radioshack.com/sm-2-sided-copper-clad-pc-board--pi-2102495.html copper-clad board] for our circuit (see image).  However, due to the way this board is set up, this attempt only works with exact precision.  Unfortunately, due to the limited number of IR transceivers and copper-clad boards we had this approach led to a dead end.  Another possible solution to mount the IR transceiver was to use a [http://www.schmartboard.com/index.asp?page=products_so&id=54 SchmartBoard].  These boards are more general and pre-fabricated for use with surface mount ICs (with a particular pitch or pin seperation).  Theoretically, both solutions will allow for connections to a solderless breadboard.  However, because none of the IR transceiver chips we could find came at the same pitch as the SchmartBoards, we could not use this approach.  Overall, since the IR transceiver chips did not come at standard pitches, we were unable to find a way to mount the IR chip.-->