Using an FTDI PCB (with Vishay infrared receivers and emitters) as the basis for the project provides added benefits to my development including the following:
- FTDI for infrared uses USB to TTL, however the same chips are more commonly used for RS-232 (which I plan to work on further down the line although I have done some initial experimenting with RS-232 and am familiar with FTDI USB to RS-232 devices).
- As with most USB devices, they come with a unique serial number which can be retrieved when interrogating the device.
- The EEPROM which stores the serial numbers is freely programmable from a number of operating systems which may be of use at a later date – I have experimented with programming non-FTDI USB to RS-232, such as the Prolific 2303, converters in the past without much success.
- Readily available worldwide and relatively cheap.
- Available in a range of formats, pre-moulded cables, chips / ICs and PCB modules.
Hardware in detail
The FTDI TTL-232R-5V-PCB is also available in a 3 volt version – the models are almost identical and only differ by the presence of R1 on the 5V model and R2 on the 3V version. Useful to know if you have one lying around and aren’t sure which model it is. The board is a basic USB to TTL serial converter and detailed information, schematics and EEPROM settings can be found in the datasheet online – I’m using these modules in their factory default states without any modifications to internal settings.
As most consumer remote controls operate at 38khz I opted for 38khz receivers and emitters (this decision on make / model was influenced by the fact that I had some TSOP38238 emitters lying around when first experimenting) but other receivers should work.
Transmitter – The following diagram shows the wiring of the infrared emitter to the FTDI PCB.
Receiver – Infrared receiver pin-outs and corresponding pads on the USB module. The ground (‘GND’) pad highlighted by the dotted border indicating that the pad is on the underside of the module.
As can be seen, only the ground pad is common between the two diagrams so combining the emitter and receiver onto one module would be achievable.
I’ve taken a few photographs of the hardware I’m using to get an idea of schematics in physical form and to demonstrate the scale of the modules.
Transmitter – using the original Keene Electronics IRUW wired emitter with lens (photos taken before obtaining the smaller blue Vishay emitter).
Receiver – leads of the component are soldered directly to the board (no additional wiring)
I have spent a bit of time searching for cases and alternative ways of housing the modules – there is a neat case manufactured by New Age Enclosures which is what the IR Blaster products use however it seems that resellers only make these available in bulk quantities so for now they will stay as they are until I manage to find something more suitable.