Android Question 2 Hz pulses

[stari]

Hello,
anybody knows, how to produce 2 Hz square wave pulses ? I need pulses for switching LEd on and OFF , in rhitmus 2 Hz.

 

[Erel]

Use a timer to change the value from 1 to 0 every 0.5 second.

 

[stari]

Use a timer to change the value from 1 to 0 every 0.5 second.

Erel, thks. I know that. But, how can i switch , for example, an LED On/OFF without additional hardware ? Can i switch, for example, USB power pin ON/OFF ?

 

[Erel]

This is more difficult. You can use a Usb to serial converter and then use it to control a LED (see UsbSerial library).

 

[fatman]

Without additional hardware you may use the internal flash:
http://www.b4x.com/android/forum/threads/flashlight-app.11664/

Fatman

 

[stari]

Without additional hardware you may use the internal flash:
http://www.b4x.com/android/forum/threads/flashlight-app.11664/

Fatman

Fatman, thank you. this solution is known by me. But, ..., i wish to turn on/off an external LED. Mybe over audio port? Or USB - eg. switching USB power pin on/off ? Is this possible ?
Thank you.

 

[stevel05]

Have a look at this, and go with Erel's answer: http://stackoverflow.com/questions/1925237/control-usb-ports-power

 

[strat]

By using audio output, you can drive a transistor to flashing a led. Simple BJT circuit can easily turn on a 20 mA small led.

 

[Michael Gasperi]

The peak audio output is about 1/2V which is too low for an LED by itself. Strat's idea is a good one if you have an external power source. You might be able to use an audio output transformer backwards (for example Radio Shack 273-1380) to kick up the voltage to something an LED would need.

 

[stari]

Have a look at this, and go with Erel's answer: http://stackoverflow.com/questions/1925237/control-usb-ports-power

ok, i will try.

 

[stari]

The peak audio output is about 1/2V which is too low for an LED by itself. Strat's idea is a good one if you have an external power source. You might be able to use an audio output transformer backwards (for example Radio Shack 273-1380) to kick up the voltage to something an LED would need.

I don't have an external sourc, or i don't wish to use it. Transformer will be Ok, i will try.