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Need to use already used pins on Stellaris LM4F120 LaunchPad

Ankur
Prodigy 165 points

Hi,

is it possible to use below mentioned pin for other purpose(for e.g for SSI interface) on Stellaris LM4F120 LaunchPad Evaluation Kit as these are connected on board LED's using 0 ohm resistor.

PF1,PF2,PF3

If yes, Please provide details

  • 0
    Guru 35565 points

    Ankur said:
    these are connected on board LED's using 0 ohm resistor

    So, if you remove the zero-ohm resistors, they will no longer be connected to anything - will they?

     

  • 0
    Guru 117855 points

    Ankur said:
    If yes, Please provide details

    As board is complete/built - you should minimize any extra soldering to prevent damage to fine traces.  Suggest that you remove the 3 smt resistors (mentioned) and then, "tombstone" (stand them up vertically) them by tack soldering them to the MCU side of the resistor's original pad/connection.  You may then tack solder an appropriate lead to the top of each, standing resistor - which minimizes stress upon the pcb trace.

    Should you want to "reclaim" or use the board's Leds - you may tombstone a different resistor on the original resistors'  vacated pad.  Tack a lead - as above - and you have reclaimed 3 MCU pins and 3 Leds - for your future use.

    Suggest that you, "anchor" each lead so none place any strain upon their "tombstone" supports.  We usually solder each lead to a standard, 0.100" male header - and then firmly support the header to a piece of pcb material.  In this manner connections are quick, secure and easy...

  • 0 in reply to cb1_mobile
    Prodigy 165 points

    Thanks for reply

    One more question, instead of "tombstone" them , can i completely remove these resistor as i would not be using leds in future

  • 0 in reply to Ankur
    Guru 117855 points

    Ankur said:
    as i would not be using leds in future

    Suggested tombstoning as it is unlikely to damage your pcb - while providing a quick/easy connection point for your future use.  Of course you can solder directly to the pad of the removed resistor - but any future strain upon your exiting lead will likely, "pull" that pcb trace - and then you have a mess!

    We're fortunate to have immediate access to multiple scopes, function/signal generators etc.  Yet simple Led remains often our "first/best" choice for basic, "Sanity Checks" and efficient, "test/verify."  Simply faster to set-up than a scope - no trigger adjustments, probe anchoring/slipping, loss of desk real estate etc.   I am certain that you will - sometime in the future - be glad that you have "eased access" to multiple Leds.  

    Should you decide to use the Leds - insure that somewhere in the Led circuit proper current limiting resistors are present.  And always insure that any signal leads leaving your board are, "strain relieved" - so that they do not, "pull away" the fine traces on your Eval Board...