IR remote + STM32 to usb, schematics

Fistly I need a stable physical connection between remote and microcontroller.

IR receiver

From every TV we can extract complete solution. This part not only receive IR signal, it also have AGC circuit in order to receive the signal in wide range of distances between LED and photodiode. Output is TTL compatible. Here is it's internal schematic.

A lot of cheap analogues TL1838, TSOP4838, TSOP38238. Note that last two digits means the carrier frequency in kHz. Tipycal is 38kHz.

IR codes

Basic information about codes. In the web there is not to much information about IR remotes codes, but I founded this documentation. In general terms there is three types of a signal modulation (i.e. representations of one bit), a bi-phase coding, pulse distance coding and a pulse length code. But mainly we deal with RC5 protocol who uses a bi-phase coding, in what logic 1 is defined as an 889-μs space period followed by an 889-μs carrier modulated pulse period. Logic 0 is defined as an 889-μs carrier modulated pulse period followed by an 889-μs space period. See picture.

IR remote sends a package in order to signal about a button push. There is no matter to consider a packet format in that post, it's rather faster to reverse it by reading information from IR which I have.

Not working variant.

Also I thought about simple variant with simple phototransistor. It showed quiet good results, but only for 1 meter distance for a bigger range all circuits from previous point are needed. Here is a schematic, photo of part and a whole experiment.

 

Device schematic.

Total schematic is typical, includes a controller, IR port and USB port. But I also add additional control channel. It can be connected to the motherboard and it will add opportunity to switch on a PC like a usual TV through remote.