Electrical – High-speed Infrared UART link with photodiode

comparatorinfraredoperational-amplifierphotodiode

I need short-distance (about few centimeters) wireless IR UART link with 250k+ baud. I tried to use phototransistor (assume Q1 is phototransistor). Q3 is used to prevent inverting signal.

schematic

simulate this circuit – Schematic created using CircuitLab

With this schematic I reach 57600 baud with Arduino. Now I am looking for photodiode schematic and I hope that it can be faster.

I found out tipical application with transimpedance amplifier. Something like this:

schematic

simulate this circuit

Is this suitable for my application? What about environment light adjustment? Also, can I use this circuit with unipolar supply?

Maybe comparator will be more suitable for my application, because I need only binary signal and don't care about amplifier linearity etc, but I have no idea how to use comparator instead of op-amp in this chematics.

UPD #1:

  1. I replace R1 with 100 Ohm and reach 115200 kbit/s
  2. I know about IrDA, but environment light isn't a really big problem in my case. I can protect optocoupler from environment light.

Best Answer

It is a bit more challenging. You need to protect your channel from variations in ambient light, which can be horrendous. That's why IrDA (infrared digital communication alliance) uses modulated light and a sophisticated automatic gain control system. Current IrDA standard extends the data rate to 4 Mbps, see the article.

The IrDA standard has successfully progressed from IrDA-1.0 (115.2Kbps) to IrDA-1.1 (4Mbps) in the short two and half years. There are many components, adapters, software and mobile systems available for the IrDA-1.0 standard on the market now. The same will happen soon for IrDA-1.1 standard with the optoelectronic, analog and digital interface ASIC components already on the market.

Today at IrDA 1.4 there are "medium" IR (MIR) transeivers (1.152 mbps) TFDU5307, FIR (fast infrared 4 Mbps) transceivers like TFDU6300 which are still available.

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There were plans for VFIR (16 Mpps channels), but it looks like this direction didn't get enough industrial traction. VFIR transceiver TFDU8108 is however available.