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HP C4103A2 FIR as sensor? — Parallax Forums

HP C4103A2 FIR as sensor?

JohnGayJohnGay Posts: 57
edited 2012-05-20 14:29 in Accessories
We had several of these lying about going to waste and I was wondering if I could make some kind of sensor out of it.

It's a 4Mbs Fast Infrared transceiver that use to come with their printers. It's got an 8-pin Mini-DIN and I've found the pinout in it's users manual on-line:

1 (Ind LED) -SIG_DETECT
2 (single-end) -RX_SIR
3 (diff data) -TX
4 (ground) -PWR_GND
5 (diff data) -RX_FIR
6 (diff data) +TX
7 (5 Volt) +5V
8 (diff data) +RX_FIR

It says it has about a 1 meter range and 15Degree beam. I know it can't be used for range sensing, but I was wondering if this would work as a general sensor?
Another idea is to use it for comms between an autonomous robot and a base/charging station.

Without a clock pin, I'm guessing I can just feed data/pulses into this and watch the receive side? Also, if it runs on 5V to ground, does that indicate that the diff data is also 5V-GND?

Any thoughts or feedback would be appreciated.

Cheers,

John Gay

Comments

  • JohnGayJohnGay Posts: 57
    edited 2012-05-20 05:51
    OK, I plugged this into my QuickStart and started playing with it today.
    I can get the top LED to light up. I can flash the IR LED, but I can't get any indication there's something in front of it. I can see a remote control flashing, but reflections don't seem to register.
  • Mike GreenMike Green Posts: 23,101
    edited 2012-05-20 11:12
    These use a very specialized IR protocol (see here for a starting point). The receiver has circuitry to detect and handle the very short IR pulses involved to make it easier for subsequent circuitry to handle the higher level protocols.
  • JohnGayJohnGay Posts: 57
    edited 2012-05-20 13:32
    Actually, the only circuitry it contains is this http://www.ti.com/product/ds90lv019 differential line driver and this http://www.fairchildsemi.com/an/AN/AN-314.pdf ttl-cmos adaptor. So it would seem the logic was in the printer. http://www.colin99.co.uk/extras/irda/hp_c4103a_irda.htm has a good picture of the inside.

    I'm afraid that it probably can't transmit and receive simultainiously which would defeat the purpose of using it as a sensor by it's self. Two seperate units might work. Another option is for a comm-link between the robot and other devices like a docking/programming station.

    Thanks for the link, though. But what I really need is programming help (-=
  • Mike GreenMike Green Posts: 23,101
    edited 2012-05-20 14:29
    The IR transceiver contains the signal conditioning I mentioned. You could try one of the serial communications drivers in half-duplex mode. You would need to flush the receive buffer after you finish transmitting since the receiver would see anything transmitted. You'd want to use RXD-A for receiving since that's optimized for typical Bauds you'd use. You'd probably want to use inverted mode so the IR LED is off most of the time (when the serial line is idle). You'd need some kind of sync preamble to messages so the IR receiver would have time to adjust to the incoming signal level. You could just turn on the IR LED for a character time or two before sending some kind of sync character and have the receiver at the other end ignore the input until a sync character is seen.
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