- Blog entry posted in 'Electronics and Other Ramblings...', May 29, 2012.
Looking for some cool stuff to add playtime with the kids, we found the Phoenix LTX Lazer Tag from Hasbro.
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The system consists of two guns which use infra-red (IR) to “communicate” with each other. There are two modes of operation:
1. Free Play (everybody against everybody else)
2. Team Play (team 1 vs. team 2)
The system is based on IR transmitter and receiver integrated into the same gun. The IR transmitter/receiver uses 38kHz modulation and simple pulse width modulation for communications. The system operates very well both inside and outside the house. But after a while we wanted to add more guns and/or targets. Of course the first step to do this is to figure out the actual operation. A quick search of the web says that the units use 38kHz IR transmitters and receivers. Using the already built IR receive module shown in “Basic IR Communications” and the Saleae Logic, the LTX systems were decoded with ease. Typical transmissions are as follows.
• If Free Play is selected
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• If Team Play – Team1 is selected
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• If Team Play – Team2 is selected
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For the initial trial, we used the already built IR receive and transmit modules form “Basic IR Communications” to simulate the LTX Lazer Tag system. We got really good results and range with the transmitter and the LTX system as a receiver, and easy decoding with the receiver and the LTX system as a transmitter; even though the receive and transmit modules were used at 40kHz; instead of the 38kHz the LTX system uses.
Next step; use the 38kHz modulation for both transmit and receive; and modify a NERF gun to use it.
Oshonsoft code used for transmitter checkout:
'* PIC12F683 * Phoenix LTX Lazer Tag *'
'Title: Lazer Tag Transmitter
'Description: Uses MCU to decode Lazer Tag information from Phoenix LTX
'Author: languer (©2012)
'Pin Allocation:
'PIN# Main_Fn Secondary_Fn
'GP0 -> RS232_OUT ICSP-DAT
'GP1 -> TAG_OUT ICSP-CLK
'GP2 -> PWM_OUT
'GP3 -> MCLR
'GP4 -> TAG_IN
'GP5 -> TEAM_IN
'Usage Information:
'RS232 Baud Rate: 9600bps
'Version Info: v1
'-> internal clock @ 8MHz
'-> RS232 output
'-> IR transmitter output decoding
'General Configuration
Define CONF_WORD = 0x33c4 'for internal 8MHz osc
'Oscillator/Clock Configuration for internal 8MHz osc
Define CLOCK_FREQUENCY = 8
OSCCON = 0x71
'Debug Option
Dim debug As Bit
debug = True
debug = False
'Variable Declarations
'>>I/O
Symbol rs232_out = GP0 'rs232 output
Symbol tag_out = GP1 'tag led output
Symbol pwm_out = GP2 'pwm output
Symbol tag_in = GP4 'tag/trigger input
Symbol team_in = GP5 'team select input
'>>Constants
Const _trisio = %11111000
'>>Variables
Dim _true As Bit
Dim _false As Bit
_true = True
_false = False
Dim data As Word
Dim decoded_data As Byte
Dim cnt As Byte
Dim flag_start As Bit
'Main Program
main:
If debug = _false Then
WaitMs 2500
Endif
Call init()
While _true
If tag_in = 0 Then
Select Case team_in
Case 0
Call pwm_enable()
Call team1_tag()
Call pwm_disable()
If debug = _false Then
WaitMs 200 'debounce
Endif
'wait until tag button is released
While tag_in = 0
Wend
Case 1
Call pwm_enable()
Call team2_tag()
Call pwm_disable()
If debug = _false Then
WaitMs 200 'debounce
Endif
'wait until tag button is released
While tag_in = 0
Wend
EndSelect
Endif
Wend
End
Proc init()
AllDigital
TRISIO = _trisio
'pwm settings
'>>>pwm period to 40kHz
PR2 = 49
'>>>pwm duty cycle to 50%
CCPR1L = 25 'using 8-bit mode (for 10-bit mode, 100 would be written to CCPR1L:CCP1CON<5:4>)
'>>>pwm tmr2 prescaler 1:1 (for 40kHz)
T2CON.T2CKPS1 = 0
T2CON.T2CKPS0 = 0
'>>>pwm tmr2 enable
T2CON.TMR2ON = 1
'>>>pwm enable
CCP1CON.CCP1M3 = 1
CCP1CON.CCP1M2 = 1
CCP1CON.CCP1M1 = 0
CCP1CON.CCP1M0 = 0
Low pwm_out
Low tag_out
If debug = _false Then
Serout rs232_out, 9600, "Phoenix LTX Lazer Tag Transmitter", CrLf
Endif
End Proc
Proc pwm_enable()
'>>>pwm enable
CCP1CON.CCP1M3 = 1
CCP1CON.CCP1M2 = 1
CCP1CON.CCP1M1 = 0
CCP1CON.CCP1M0 = 0
End Proc
Proc pwm_disable()
'>>>pwm disable
CCP1CON.CCP1M3 = 0
CCP1CON.CCP1M2 = 0
CCP1CON.CCP1M1 = 0
CCP1CON.CCP1M0 = 0
End Proc
Proc team2_tag()
'preamble
Low tag_out
WaitMs 6
High tag_out
WaitMs 3
'bit7 (1)
Low tag_out
WaitMs 6
High tag_out
WaitMs 3
'bit6 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'bit5 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'bit4 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'bit3 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'bit2 (1)
Low tag_out
WaitMs 2
High tag_out
WaitMs 2
'bit1 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'bit0 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'finish
Low tag_out
Serout rs232_out, 9600, "team2", CrLf
End Proc
Proc team1_tag()
'preamble
Low tag_out
WaitMs 6
High tag_out
WaitMs 3
'bit7 (1)
Low tag_out
WaitMs 6
High tag_out
WaitMs 3
'bit6 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'bit5 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'bit4 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'bit3 (1)
Low tag_out
WaitMs 2
High tag_out
WaitMs 2
'bit2 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'bit1 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'bit0 (0)
Low tag_out
WaitMs 2
High tag_out
WaitMs 1
'finish
Low tag_out
Serout rs232_out, 9600, "team1", CrLf
End Proc
Code used for receiver checkout:
'* PIC12F683 * Phoenix LTX Lazer Tag *'
'Title: Lazer Tag Receiver
'Description: Uses MCU to decode Lazer Tag information from Phoenix LTX
'Author: languer (©2012)
'Pin Allocation:
'PIN# Main_Fn Secondary_Fn
'GP0 -> RS232_OUT ICSP-DAT
'GP1 -> ALLPLAY_OUT ICSP-CLK
'GP2 -> TAG_IN
'GP3 -> MCLR
'GP4 -> TEAM1_OUT
'GP5 -> TEAM2_OUT
'Usage Information:
'RS232 Baud Rate: 9600bps
'Version Info: v1
'-> internal clock @ 8MHz
'-> RS232 output
'-> IR receiver input decoding
'General Configuration
Define CONF_WORD = 0x33c4 'for internal 8MHz osc
'Oscillator/Clock Configuration for internal 8MHz osc
Define CLOCK_FREQUENCY = 8
OSCCON = 0x71
'Debug Option
Dim debug As Bit
debug = True
debug = False
'Variable Declarations
'>>I/O
Symbol rs232_out = GP0 'rs232 output
Symbol tag_in = GP2 'ir receiver input
Symbol allplay_out = GP1 'team1 tag led out
Symbol team1_out = GP4 'team1 tag led out
Symbol team2_out = GP5 'team1 tag led out
'>>Constants
Const _trisio = %11001100
'>>Variables
Dim _true As Bit
Dim _false As Bit
_true = True
_false = False
Dim data As Word
Dim decoded_data As Byte
Dim cnt As Byte
Dim flag_start As Bit
'Main Program
main:
If debug = _false Then
WaitMs 2500
Endif
Call init()
While _true
data = func_pulsein()
If data > 500 Then
If flag_start = False Then
If data > 2500 Then
flag_start = True
decoded_data = 0
cnt = 0
Endif
Else
If data > 1500 Then
decoded_data = ShiftLeft(decoded_data, 1)
decoded_data = decoded_data + 1
Else
decoded_data = ShiftLeft(decoded_data, 1)
Endif
If cnt = 7 Then
flag_start = False
Select Case decoded_data
Case %10000000
High allplay_out
Serout rs232_out, 9600, "all play", CrLf
Low allplay_out
Case %10000100
High team1_out
Serout rs232_out, 9600, "team1", CrLf
Low team1_out
Case %10001000
High team2_out
Serout rs232_out, 9600, "team2", CrLf
Low team2_out
Case Else
High allplay_out
High team1_out
High team2_out
Serout rs232_out, 9600, "team1", CrLf
Low allplay_out
Low team1_out
Low team2_out
EndSelect
Else
cnt = cnt + 1
Endif
Endif
Else
flag_start = False
Endif
Wend
End
Proc init()
AllDigital
TRISIO = _trisio
'set TMR0 to tick every 32us (~30)
OPTION.PSA = 0 'assign prescaler to TMR0
'set TMR0 prescaler to 1:64
OPTION.PS2 = 1
OPTION.PS1 = 0
OPTION.PS0 = 1
OPTION.T0CS = 0
flag_start = 0
Low allplay_out
Low team1_out
Low team2_out
If debug = _false Then
Serout rs232_out, 9600, "Phoenix LTX Lazer Tag Receiver", CrLf
Endif
End Proc
Function func_pulsein() As Word
Dim temp_byte As Byte
While Not tag_in
'wait for rising edge
Wend
TMR0 = 0
INTCON.T0IF = 0
While tag_in
'wait for falling edge
Wend
temp_byte = TMR0
If INTCON.T0IF = True Then
func_pulsein = 0
Else
func_pulsein = temp_byte * 30
Endif
End Function
