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CCS/SW-EK-TM4C123GXL: LED displays

William Herschel
Intellectual 640 points
Part Number: SW-EK-TM4C123GXL

Tool/software: Code Composer Studio

Hi,

Can anybody help me get started connecting and programming an LED&KEY 8  segemnt LED display to the Launch Pad?

Thank you very much

  • 0
    Guru 117850 points

    Greetings,

    Help is likely - yet your providing the 'Data Sheet/Tech Specs' of your proposed device is sure to, 'speed, ease & enhance' your support.

    You may not (yet) realize that 'there exist many' such Led & Keypad implementations - minus your specifics - 'extra time & effort' are forced upon your 'helpers.'   (And the assistance (in the dark) helpers supply - may not 'match' your unique design requirements...)

  • 0 in reply to Charles Tsai
    Guru 117850 points

    Hi Charles,

    You are an aware & skilled investigator indeed - thank you.   Do note - that past poster provided 'adequate detail' - which enabled a clear understanding of what he sought.

    When such clarity & guidance is not provided - the helper's path is lengthened - and not always to the poster's benefit...

  • 0 in reply to cb1_mobile
    Intellectual 640 points

    Hello cb1_mobile,

    Thank you for your reply.

    I did assume the LED&KEY logo would identify it but here are some more details:

    there is an Arduino project here and a data sheet for the TM1638.

    http://arduinolearning.com/learning/basics/arduino-tm1638-module.php

     

    https://arduinolearning.s3.amazonaws.com/TM1638English%20version.pdf

     

  • 0 in reply to William Herschel
    Guru 117850 points

    Greetings,

    OK - got it.   Do understand that there are a multitude of items available - our 11 person firm cannot know nor recognize them all.

    My group seeks to, 'Expand your selection process' - even though - especially though - that's not your immediate wish.

    The device you mentioned includes:

    • 8 - 7 segment Leds
    • 8 - momentary switches (push-buttons)
    • 8 - Led indicators
    • another vendor's IC 'TM1638'
    • and possibly another vendor's MCU 

    The most appealing factor of this device is (surely) its low cost.   (~3 (USD))

    This forum aims to promote the successful use of this vendor's TM4C MCUs (now designated as 'other') and so there is likely to be (unneeded & unwanted) 'duplication' between the existing 'display/keypad' device and the TM4C MCU.     This 'lessens' the appeal of this device - does it not?

    Other weaknesses noted include:

    • only numerals & a (very) few characters are accommodated by the 7 Segment Leds.   (A,C,E,F,H,I,J,O,P,U - that's just 10 out of 26!)
    • only 8 switches are accommodated - a standard keypad would (usually) include 12.   (digits 0-9, Clear & Enter)    Note too - all switches are 'unlabeled' - thus such a device requires much, 'Added design, labor & cost' - to 'escape its clearly 'amateur status.'

    My young staff expects that 'you' - like they - will shortly far 'out-grow' so limited a display and 'keypad-less' device!   (they employed a similar low cost device - and quickly came to 'hate it!')

    As an alternative - might a, 'Multi-Line Character LCD' accompanied w/(either) 12 key (or 16 key) keypad and indicator Leds - prove more attractive?    Such a device would fully & properly mate w/the TM4C family of MCUs - and may operate via: Multiple Serial (I2C, SPI, UART) or Parallel Interface.   (or a combination of the two)    Further - this much enhanced device enables you to: 'Display MEANINGFUL MESSAGES - rather than cryptic, stunted & numeric only ones' (via led&key) while delivering 32 (2 x 16) or 80 (4 x 20) - 5x7 crisp, dot matrix Characters!)

    Now to your request for, "Getting Started w/Connecting & Programming:"

    Have you specific questions regarding the 'connection?'   Both the powering & signalling should be included.    My small firm believes it best that each user 'Invest (some) time in such an investigation' - and in that process generate 'proper/informed' questions.    May we start w/you - there?

    As to programming - our short investigation has revealed (nearly) complete Arduino Code - prepared by multiple sources.    As Arduino employs a far simpler MCU - that code is not compatible w/the TM4C's API - yet it IS possible to, 'Create a general code translator' - which will enable the TM4C to control your device.    (at the cost of time & effort - which may not be justified...)

    As strong proponents of 'KISS' - the identification of the 'Key Code Blocks' (presently achieved via Arduino Code) is a necessary, 'First Step.'   As each code block is identified - suitable conversion to TM4C API code may be systematically performed.     We believe this to be 'exactly' what you 'should be seeking.'

    OR - and importantly - there may be (other) methods to create code for 'your modified device' AND AT THE SAME TIME - 'Provide for the superior LCD & (real) Keypad - earlier proposed.    This code would bear NO Arduino capability (which EATS time/effort - and 'Degrades performance!') - instead be 'TM4C API optimized' - which will far better 'resonate' w/many/most here...

  • 0 in reply to cb1_mobile
    Intellectual 640 points

    Hello cb1_mobile,

    Thank you for your expansive reply. I appreciate nebulous questions can be irritating to experts but they normally reflect the ignorance of the novitiate which is true in my case. I am going to investigate the suggestions you make and come back with specific questions. Without you and others on this forum it would be pretty difficult to make any headway in this arcane art sometimes.

    Best wishes

    William

  • 0 in reply to Charles Tsai
    Intellectual 640 points

    Thanks Charles. I shall study that.

  • 0 in reply to William Herschel
    Guru 117850 points

    Hello back,

    Staff is glad to note your acceptance of what they (and I) believe to be - a superior selection path.    They have 'added to' their initial posting - and offered further items for your consideration.    (And have color coded their posting to match your request for, 'Getting Started.')

    The '7 Segment Display' (developed by women by the way ... most of the staff here are young women) was 'iconic' - yet its inability to display 'all of the available characters' - has (rightfully) limited its use in the modern era.   Thus the choice of 'only' a 7 Segment Display deserves 'needed consideration.'     (which we strove to justify & supply.)

    Every field has its unique 'acronym-laced vocabulary' - yet electronics & programming - at least - fall back upon 'logic & reason.'    (most often...)

    BTW - one staffer had a friend who had purchased an 'early version' of your (initial) device.    She too was 'grabbed' by the 3 (USD) price - yet noted the display ceased scanning - and failed - w/in the first 10 days of operation.    Sometimes - low cost must (not) be one's major consideration.

    Note too that the combination of a 'proper display & keypad' provides an excellent technical inroad to the MCU.   

    Users well learn & master:

    • Writing Data
    • Reading Data
    • Sending Messages (to the display)
    • Receiving Messages (from some remote device - perhaps a sensor)
    • Interacting w/multiple sensors
    • Controlling Motors (even several motors)
    • And many other 'Features, functions & benefits' (credit IBM) which 'MORE' than pay  for themselves

    This is why - the young staff here took the (necessary) time & interest to 'inform & advise' your (early) device choice ... so that you not 'unfairly' stunt your growth & capability...

  • 0 in reply to cb1_mobile
    Intellectual 640 points

    Hello cb1_mobile,

    I would like to use the $3 LED&Key since I have it now but I may change my mind if it’s a failure. There are three wires on it so one must do Rx / Tx as the buttons must Tx signals back to the TM4C123GXL. Presumably the segments are illuminated sequentially given there’s only one wire effectively. And presumably it’s not noticeable on the display – or is it? But my initial quandary is - I’ve no idea which GPIO pins to map to the three signal wires. The power is obvious. I would appreciate any advice on ports and pins. Just getting the thing connected and being able to talk to it would be my first step.

    Thanks

    William

  • 0 in reply to William Herschel
    Guru 117850 points

    Hello back,

    We are visiting clients this afternoon & tomorrow - our response will be necessarily short & delayed.

    The 'sequential illumination' you note is called, 'Multiplexing' - a very clever technique which reduces the number of  required connections.    This technique relies upon the 'Persistence of human/animal vision' - such that (usually) only one display element at a time is 'illuminating' - yet this happens so quickly that our brain perceives the 'grouped image' as, 'All on.'    (if you chatter your teeth - or move your head rapidly - you can note the display scanning (i.e. only one 7 segment unit will be on at any one time)  ... really that works!)    More than once I've, 'Won drinks at a bar - w/that  (drinkable) knowledge...'

    Three signals are key: 

    You have two choices in MCU signal mating:

    • employ those MCU pins which enable 'automated' signal output'
    • employ 3 MCU pins (most always) from the same MCU Port - yet w/out benefit of that 'automation.'

    The MCU's 'SPI' capability provides a 'Clocked Serial' signalling - which (at quick glance) appears to provide 'automated' data flow - both to & from - the device's control IC.    This would be my group's recommendation - provided that the MCU's SPI mode can supply the (expected) relatively large number of data & clock signals the device (likely) requires.    (this last clause may prove vital to your usage...)

    Note too - SPI is (usually) a 'full-duplex' (send & receive together) operation - yet this IC demands 'half-duplex' operation.    This means that you must, 'Repurpose the SPI output (MOSI) pin' from output to input - to prevent 'contention' when the display IC switches from input to output.   (that's not easy nor fun - thus my group would not employ this slow/awkward IC...)

    Your MCU provides several SPI ports - your MCU manual reveals their location and (most - possibly all) appear on the LPad's headers.

    Hookup:   SPI_FSS to STB, SPI_Clk to CLK, SPI MOSI to DIO (when transmitting to device) SPI_MISO to DIO (when receiving from device ... assumed switch information)    You (may) be able to tie the MCU's MISO to MOSI - so long as you, 'DISABLE the MOSI pin prior to the IC's 'Start of Transmission.'   You would then receive the IC's output upon the MCU's MISO pin.   (this may prove 'way too complex' for one beginning.)

    Again - the 'beauty of SPI' is that the 'Serialization of Data' is automated - handled for you - via the MCU's SPI Engine.    You would be charged w/that effort - should you employ 'Non-SPI' means...

    If you choose the Non-SPI mode - there is no limit upon the number of data & clock signals you can (properly) produce.    Yet - all of the data 'packaging' which is provided by SPI is lost - and that data organization and serialization - falls entirely upon you.

    Note - my group would (not) use this IC - so our assistance (may) enable our answering of specific design-related questions - yet we prefer to 'avoid mastering' any device we see of (pardon) much reduced value...   

    As w/most things w/in engineering - 'Trade-Offs are required' - each application is unique - and demands its own analysis & resolution...    And - sitting unsaid ... 'Can a 3 (USD) device 'justify' hundreds of (USD) in support?'

    We believe that we've 'well answered' (perhaps even exhaustively answered) your 'Help getting Started' and would appreciate your marking one or more of (our) posts as, 'having Resolved' your 'Getting Started Issue.'

  • 0 in reply to cb1_mobile
    Intellectual 640 points

    I look forward to your signals. I have been known to move my head rapidly in a bar but never profited by it.

  • 0 in reply to William Herschel
    Guru 117850 points

    William Herschel said:
    I have been known to move my head rapidly in a bar but never profited by it.

    Aha - profit depends upon:

    • the chosen bar
    • speed of head movement
    • multiplex rate of the 'cash generating display'

    We were 'stuck in traffic' (I shut my eyes tightly) when young staff drives - & was able to write more than expected.   (but only when we were, 'Stopped at lights' - so I could open my eyes!)   

    Do give a reread of the earlier post - we are 'radio silent' now till our series of client meetings end.

  • 0 in reply to cb1_mobile
    Intellectual 640 points

    Hello cb1_mobile,

    You have been more than generous in the time you have spent on this which I appreciate and will now mark the appropriate post as resolved.

    Cheers

    William

     

  • 0 in reply to William Herschel
    Guru 117850 points

    Hi back,

    Thank you Mr. Herschel - appreciated.

    Do consider - we've been 'in this field' long enough to be able to 'predict' what (likely) 'Will or Will Not Satisfy.'    You are almost certain to quickly 'outgrow' this (most limited) device - what then?    Should you devote your - and others - time & effort to struggle to (maybe) master a (pardon) 'performance-lite device?'

    Is it not much better to employ a 'Far more mainstream Display/Keypad' - which employs a REAL SPI interface - and which enables the 'Creation AND Display of 'Meaningful (human readable) Messages' - rather than those, 'Cryptic, Stunted (i.e. meaning-lite) numeric-heavy/only 'impostors?'

    As one who was fortunate to 'wildly succeed' w/in the display field - I'm able to 'Inform & Advise' that Tech 'Panel Space' is at a 'Premium' - and such a 'Low Level Device' would rarely be awarded the most Critical 'User Panel Residence.'

  • 0 in reply to cb1_mobile
    Guru 117850 points

    Greetings,

    Under the assumption that, "1 photo meets/exceeds 1000 words" the following is attached.   

    Shown is a:

    • 6 Digit, 7 Segment LED Display (employed due to its size - yielding higher impact & longer distance viewing)
    • 2 x 20 Vacuum Fluorescent Display (provides 'vital meaning' to the 'numeric only' LED) - while doing unique 'double duty' by 'labeling' the function keys) - adding (unlimited) switch functionality!
    • 6 tactile 'switches/keys' - 4 of which are 'soft-keys' - which may govern multiple functions - each 'defined' by the display

    Note how the addition of a Character Display (in this case - a 2x20 VFD) and the use of 'Soft-Keys' (panel switches which are 'labeled & changed' via display software) enable a reduction in, 'Panel Real Estate' - yet without compromising 'Switch Meaning!'   (i.e. those 4 function keys (F1-F4) may allow 'tens, even hundreds' of unique operations to be 'commanded!') 

    Many variations of the above may be designed - do accept the fact that 'Panel Real Estate' is 'At a Premium' - and Displays MINUS Clear Definition - are (highly unlikely) to succeed in today's market-place... 

    The (clever) reduction of panel components - as shown above - drives down both 'Material Costs & Labor' - while adding great 'Functionality, Flexibility & User Ease' to any product...