Hi,
I was wondering if anybody could shed some light on how a guy has managed to achieve 3 things in this circuit and if they are possible to do on a picaxe:-
http://www.lasertagparts.com/images/MT CORE RevH 01.gif
1. Basically on the PIC in the diagram, pin 11 and 13 turn on two FETs which modulate serial data over a 38khz pwm carrier wave. Somehow the guy is also able to detect if current is flowing through the pwm FET to know if the IR led is functioning/connected. Anybody know how this is done.
2. Using either pin 27, 21 he is also able to detect if the IR receiver is connected. I am guessing that he might be relying on the fact that IR recievers output 5v when they are not receiving, but if it was not connected, would you not need a pulldown resistor to stop the pin floating?
3. He uses pin2 to control a LCD display but can also measure the voltage between the two 1k65 resistors. How is this possible??? Surely the voltage would upset the data going to the LCD, or because it will only be 3.6v (1/2 of 7.2v), it neither registers as on or off? Even further still how can he be using a pin as both an input and output at the same time???
Sorry for a load of questions in one go, but its really been bugging me how it works. I'm afraid he doesn't give out the source code, which makes this hard to guess how it works.
I was wondering if anybody could shed some light on how a guy has managed to achieve 3 things in this circuit and if they are possible to do on a picaxe:-
http://www.lasertagparts.com/images/MT CORE RevH 01.gif
1. Basically on the PIC in the diagram, pin 11 and 13 turn on two FETs which modulate serial data over a 38khz pwm carrier wave. Somehow the guy is also able to detect if current is flowing through the pwm FET to know if the IR led is functioning/connected. Anybody know how this is done.
2. Using either pin 27, 21 he is also able to detect if the IR receiver is connected. I am guessing that he might be relying on the fact that IR recievers output 5v when they are not receiving, but if it was not connected, would you not need a pulldown resistor to stop the pin floating?
3. He uses pin2 to control a LCD display but can also measure the voltage between the two 1k65 resistors. How is this possible??? Surely the voltage would upset the data going to the LCD, or because it will only be 3.6v (1/2 of 7.2v), it neither registers as on or off? Even further still how can he be using a pin as both an input and output at the same time???
Sorry for a load of questions in one go, but its really been bugging me how it works. I'm afraid he doesn't give out the source code, which makes this hard to guess how it works.