Phoenix LTX Accessory Connector
This is the numbering of the connector's pads when looking at the bottom of the tagger with the barrel pointed up or away from you.
|Pad||Name||Description||Direction from Tagger|
|3||IRSIGNAL||Infrared Receiver Signal||Input/Output|
|4||COM-O||Communications Port Output||Output|
|5||COM-I||Communications Port Input||Input|
|6||INHIBIT||Inhibit Tagger Infrared Emitters||Input|
|7||LAZERMOD||Infrared Emitter Signal||Output|
PGND is used for high current paths such as the infrared emitters. If an accessory includes a voltage regulator, it should be referenced to PGND.
SGND is used for sensitive signal paths such as the infrared receivers. It is used as the ground reference for the COM-O and COM-I lines. Any noise on the SGND line will degrade performance of the infrared receivers in the tagger's dome. Signals referenced to SGND should be kept below 5mA total and should not include any high frequency components above 1kHz.
Infrared Receiver Signal
IRSIGNAL is the output of the infrared receivers in the tagger's dome. IRSIGNAL is active-low. The line is pulled high by the tagger. When an infrared signal is detected, the receiver pulls the line low.
IRSIGNAL is an open-collector bus so additional infrared receivers can be connected to it.
The tagger runs from unregulated power (3.0-4.5V) from the batteries so any receivers you connect to this line must handle being pulled-up to both above and below their reference voltage. The recommended method to do this is to use a 2N3904 NPN transistor in an open-collector configuration. Connect the output of your receivers to the base of the transistor, IRSIGNAL to the collector, and SGND to the emitter.
Communications Port Output
COM-O carries serial data out from the tagger to the accessory device. COM-O is active-low. Voltages above 0.6V represent 0 and below 0.6V represent 1.
The recommended method to connect to COM-O is to use a 2N3904 NPN transistor in an open-collector configuration. Connect COM-O to the base of the transistor through a 22kΩ resistor, the collector to your circuit, and SGND to the emitter. Connect a 47kΩ resistor from the base of the transistor to SGND to ensure fast switching.
Communications Port Input
COM-I carries serial data in to the tagger from the accessory device. COM-I is active-low. Voltages above 0.6V represent 0 and below 0.6V represent 1.
The recommended method to connect to COM-I is to use a 2N3906 PNP transistor in an open-collector configuration. Connect your circuit to the base of the transistor, the collector to COM-I, and the regulated reference voltage of your device to the emitter.
In the tagger, COM-I connects through a 15kΩ resistor to the base of a 2N3904 NPN transistor. The base of also connects to SGND through a 47kΩ resistor. The emitter connects to SGND and the collector connects to the rest of the tagger's circuitry.
Inhibit Tagger Infrared Emitters
INHIBIT is active-low. When an accessory device pulls it down toward PGND, the infrared emitter in the tagger's barrel is disabled. The accessory device should then take the LAZERMOD signal, modulate it to 38kHz, and use its own infrared emitter to send the signal.
The recommended method to connect to INHIBIT is to use a 2N3904 NPN transistor in an open-collector configuration. Connect your circuit to the base of the transistor, INHIBIT to the collector, and PGND to the emitter. Your circuit should drive the base of the transistor with enough current to ensure that the transistor is fully saturated with a 5mA collector current.
Infrared Emitter Signal
LAZERMOD is the unmodulated infrared signal from the tagger. LAZERMOD is active-low. LAZERMOD is referenced to PGND in the tagger but it may be referenced to SGND in an accessory device since it is only used as a logic input there. LAZERMOD is an output only. Pulling it low could permanently damage the tagger's processor.
The recommended method to connect to LAZERMOD is to use a 2N3904 NPN transistor in an open-collector configuration. Connect LAZERMOD to the base of the transistor through a 51kΩ or higher resistor, the collector to your circuit, and SGND to the emitter. No resistor is required from the base of the transistor to SGND as LAZERMOD is a push-pull output from the tagger's processor.
SW9V is the unregulated power from the batteries. It is switched by the tagger's main power switch and a PNP transistor controlled by the tagger's processor. When the power switch is on and the tagger has not gone to sleep from inactivity, SW9V is between 6.6 and 9.6V DC, referenced to PGND.
An accessory device can use SW9V to drive an infrared emitter as long as the following guidelines are met:
- The INHIBIT line is used to ensure that the emitter in the tagger's barrel is not active at the same time.
- It is timed so that it doesn't conflict with other high-current loads in the tagger.
- A high-quality, low-ESR capacitor of 470μF or greater is used near the infrared emitter circuit to help decouple it from the tagger's other circuits.
It is recommended that SW9V be connected to the anode of a diode and the cathode to the decoupling capacitor for the infrared emitter circuit.