Hi Andreas ! <color><param>7F00,0000,0000</param>> I think you can make a good compromise between a > simple optocoupler and IrDA. How about using Toslink? > It is commonly used for optical transmission of audio, > but you can transmit any data you want. </color>That was also my first thought when I started to work on this. However, with the new chip MCP2150 by Arizona Microchip it's very easy to implement IrDA and the IrCOMM protocol. Have a look at the data sheet !<FontFamily><param>Symbol</param> <FontFamily><param>Arial</param>This has the following advantages over Toslink: - cheaper - standard; receivers included in most computers -> no extra circuit on the pc side needed - we want bidirectional communication. If we use Toslink, we need 2 Receivers and 2 Transmitters and 2 cables. This is needed for the calibration system. Toslink or other plastic fibre systems might be very good for advanced, more complicated systems involving many channels. But I think in this case simple optocouplers and/or IrDA is cheaper and simpler. Moritz<FontFamily><param>Symbol</param> <nofill> ---------------------- Moritz von Buttlar moritz@v...