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TM4C129x launchpad LCD interfacing issue

utpal kumar
Expert 2340 points

Dear All,

I am using TIVA  C series TM4C1294 LaunchPad.

We are using OTC jumper on JP1 of LaunchPad to give +5v to the Tiva card, so we can get supply on USB pendrive.

 The problem is when we switch on the system, sometime donot out GPIO signal on LCD, & it never display after that. But other function is working like finger on serial port, TCP/IP.

 We are using EEROM for storing permanent data. On power on it is only reading the data.

 We are using ABG128064A23 LCD.  i.e. 128x 64 dot LCD working on +5v.

 We are using following GPIO as:

 1)      LCD à  PORT M for 8 bit Data bus(out)  & PORT N—2,3,4,5 bit for control line for LCD (out)

2)      LED à  PORT N 0 & 1  (out)

3)      KEY x lineà PORT P 2,3,4,5 bit for out

4)      KEY y lineà PORT E 0,1,2,3,4 bit for in

5)      Serial on PORT A using RX0/TX0, RX2/TX2, RX3/TX3

6)      VOICEà PORT F – 2,3  using PMW2&PMW3

7)      Buzzerà PORT D 4 as output

8)      I2C EERAM à PORT B 4,5 I2c 5

 

Please suggest where is the problem. Please share your valuable suggestions which will help me to resolve the issue.

Thanks & Regards :-

utpal

  • 0
    Guru 47900 points

    utpal kumar said:
    when we switch on the system, sometime do not out GPIO signal on LCD, & it never display after that.

    Have past designed, produced, and sold many such 128x64 small graphic Lcds.     Yet - we've not encountered the language, "Do not out(put) GPIO signal on the Lcd."   

    Do you mean to say that your MCU's GPIO - dedicated to both the Lcd's data, control & address - no longer toggles to specification during this failure?    Or - such GPIO signal output to the Lcd continues - yet the display appears disordered or blank?     Such detail is necessary.

    As always - might this be a "single board anomaly?"   If a single board - and a prototype - most everything becomes suspect.     Integrity of the many connections deserves your attention.    (I'm assuming yours is a "vanilla" 128x64 w/8 bit parallel bus input + control sigs)

    As you report the issue to occur @ "switch on" - might the addition of greater delay - after power on - and before Lcd initialization - improve?

    Is power adequate - for all devices connected?     Your description mentions many additional functions/accessories - power must be adequate for their total (worst case) demands.

    Suggest that you write a simple, looping program, and monitor the critical control signals - trying to detect the "onset" of the display loss.   I'd key on connection integrity - then a control signal miscue or timing violation.    Contrast voltage often is an issue - but as you report "sometimes" such failure that appears not your issue.

  • 0
    Intellectual 310 points
    Hello Utpal,

    If the issue is coming randomly (as you mentioned sometimes there is no output on GPIO),
    1. Check whether any strong pull up/ pull down on GPIO line which prevents line from toggling.
    2. This can also happen due to LCD initialization sequence and/or timing issue.