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Serial IR transmit

Topic last updated 16 Oct 2010, by Bon Thomassen. 3 replies
Bon Thomassen
15 Oct 2010

Hi,

I want to transmit debug info via Infrared. I managed to use a SFH5110-36 to receive via IR using serial rx on pin p27. Now I need a schema to connect a LD274 IR led siemens 5mm to the mbed serial tx pin p28. I know that it needs a 36 KHz carrier. How can i create it using the mbed?

 

Bon Thomassen

Shinichiro Nakamura
16 Oct 2010 . Edited: 16 Oct 2010

Dear Mr.Bon Thomassen-san

I created a library for it.

Please see the cookbook, and try it. :)

Regards

Shin.

Don Davis
16 Oct 2010

Hi Bon,

One way to generate your 36KHz carrier is to connect the IR LED between a PWM output (say p26) and the serial TxD pin. Anode to p26. Cathode to 470 Ohm resistor (or your choice depending on Vf and max If of diode and the 40mA output limit for the MBED). Other side of resistor to p28. Now, whenever TxD is Low, the LED will follow PWM out, when High, LED is off.

Set PWM period on p26 to 28uS (about 36KHz, 35714Hz) and 50% duty cycle.

Chears,

Don Davis

Bon Thomassen
16 Oct 2010

Hi Don and Shin,

 

I tried both methods and they both work. You helped me a lot.

Regards Bon