50g serial port tech. - Help.

[Vtile]

Thanks, those helps while not what I were searching for. To be fair, now I'm thought this a while I start to feel the document I remember seen somewhere propably were the hp50g IRDA-serial port tech abstract or similar. (Wondering if there could be any rumours of the part number of the IRDA transceiver/receiver module...) I'm extremely interested if it does have sensitivity control pin as do ie. Telefunken/Vishay TFDU4100 chip, that could explain the small operation distance (In Telefunken/Vishay TFDU4100 the DataSheet do say that SC high might (or will) introduce errors as:

Quote:The sensitivity control (SC) pin allows the minimum
detection irradiance threshold of the transceiver to be
lowered when set to a logic HIGH. Lowering the
irradiance threshold increases the sensitivity to
infrared signals and increases transmission range up
to 3 meters. However, setting the Pin SC to logic HIGH
also makes the transceiver more susceptable to
transmission errors due to an increased sensitivity to
fluorescent light disturbances. It is recommended to
set the Pin SC to logic LOW or left open if the increased
range is not required or if the system will be operating
in bright ambient light.

)

PS. I just opened my calc and the GND line for the serial connector is directly from batteries with common wire, the Vcc comes from PCB.. So my easy MOSFET hack, wouldn't be that easy.