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TIDA-01212: TSPF6200 analog

Rustem Avkhadiev
Genius 3550 points
Part Number: TIDA-01212
Other Parts Discussed in Thread: CC1310

Hello!

I'm trying to implement TIDA-01212 in my design and have some questions:

1. According to Vishay site,TSPF6200 IR LED is not available. Can you advise a similar LED? I can't find "Relative Spectral Sensitivity" parameter on other IR LEDs. I also tested 15 different LEDs (850-950 nm), TX part works fine, but not RX (i can see pulses on DIO28 (using oscilloscope), but voltage did not drop less then 2V).

2. That is the purpose of R2 resistor? GPIO max current is 8 mA, that is much less then LED limit.

  • 0
    TI__Intellectual 1825 points
    Hi,

    thanks for using the TIDA-01212!

    Please, find my answers below:
    1) I have not tested with an alternative LED. Nevertheless, you can use the R3 and C2 footprint (replace C2 with a Resistor) to set a voltage reference level, that fits your LED, e.g. 2.1 Volt.
    Then you can feed this 2.1 Volt COMP_REF reference to the COMPA (instead of the internal Reference used in the example) and test RX.
    Please, modify the Sensor Controller code accordingly to use this external Reference at the selected GPIO that you connected to.

    2) R2 is useful if you want to limit the current in battery operated Meters or Sub-meters to the minimum possible value.
    In general, as you wrote, you can replace it with a 0 Ohm or reduce it to allow higher current and possibly larger drop in voltage in the RX direction.

    Regards,
    Milen
  • 0 in reply to Milen
    Genius 3550 points

    Hello! Thank you for the answer!
    1. I’ve already saw this in desing guide. But how can it help my if i can’t archive stable voltage drop on RX pulse event?

  • 0 in reply to Rustem Avkhadiev
    TI__Intellectual 1825 points
    Hi,

    a few questions:

    1) how far away is the TX LED away from the RX LED?
    2) Are you driving the TX LED with CC1310 and are you absolutely sure that you have the 8mA enabled during TX?
    3) is the TX LED really capable of transmitting at 8mA?
    Some LED Datsheets, like OnSemi QED223 show data for 10mA and above; so 8mA might be too low.
    4) can you try to drive the TX LED with another MCU, eg an MSP430 device?
    Many of the MSP430 can drive up to 25mA and that should help you find out if the TX intensity then is higher and sufficient to get detected at the RX side.

    Regards,
    Milen
  • 0 in reply to Milen
    Genius 3550 points
    Hello!

    1) 1 mm
    2) yes
    3) yes
    4) Tried, no success. I also tried to use TV remote as IR-TX source - no success, i can see pulses on DIO28 (using oscilloscope), but voltage did not have stable drop (always > 2V). Then i use photodiode on RX side - all ok, but i want to use single LED.
  • 0 in reply to Rustem Avkhadiev
    TI__Intellectual 1825 points
    Hi,

    unfortunately, finding and testing a new IR LED is not a simple task, so I can't give you a solution now.

    One thing: As you have the scope connected to the probe, you are adding a lot of capacitance (unless you use an active scope probe).

    Can you try to disconnect the scope and just use the Graph Output in Sensor Controller Studio?
    basically let the tool show you if you have 0 or 1 detected - does that make a difference?

    Regards,
    Milen
  • 0 in reply to Milen
    Genius 3550 points
    Hello!
    I tried it. No luck.
  • 0 in reply to Rustem Avkhadiev
    TI__Intellectual 1825 points
    Hi,

    for now i can only recommend you to use the external voltage divider approach.
    Please, compare your LEDs to find out which gives you best sensitivity (= largest voltage drop) when you use the same TX unit. Ideally you should have a mechanical fixture or setup such that the distance between TX and RX LED is fixed.
    Choose the LED which delivers largest voltage drop in RX operation mode.
    Make sure you have a stable difference between "NO TX" and the "TX" case, where you have some voltage drop.
    Try to find a Comparator level between these two cases: e.g. you get 2.5 Volt at NO TX and 2.3 V with RX.
    Set the external voltage divider to 2.35 V and use that as an input to an DIO pin and this is fed into the COMPA as the reference.

    Hope this helps!