Forum Rule: Always post complete source code & details to reproduce any issue!
Results 1 to 2 of 2

Thread: Teensy 4.1 no headers with ILI9341 blank screen problems... soldering?

  1. #1
    Junior Member
    Join Date
    Sep 2020

    Teensy 4.1 no headers with ILI9341 blank screen problems... soldering?

    Best of days everyone!, first, thanks for reading
    (I'm a little ashamed of asking help for this trouble, because I think it is on the soldering or connections side... please point me to a safe/accurate way to test connectivity aside continuity and resistance between pins...)

    On overall sense, I'm upgrading a DUE project relating to a OSC-MIDI controller, to a Teensy 4.1 based, with 2 screens, an Audio Board and a side Serial connection to the older DUE...

    Ive been struggling with connecting the ILI9341 screen on a consistent way, because on a regular breadboard, I got it to work, with STD connections

    VCC -Vin
    GND -GND
    CS - 9
    RESET - 10K to 3.3V
    DC - 10
    SDI - 11
    SCK - 13
    LED - 110 Ohms to Vin
    SDO - 12
    T_CLK - 13
    T_CS - 14
    T_DIN - 11
    T_DO - 12

    But then, as I added the other screen, a ILI9163, they seemed to misbehave, sometimes: without changing too much, suddenly working together... then only one, then the other, etc...
    The 9163 shares MISO, MOSI, SCK, and uses 15 for CS. They worked together with the TouchPaint.Ino on the ILI9341 and the Cat eyes anim on the 9163, but sometimes, as I say; so I figured, the cheap breadboard was trascending... I went to make some little connectors with a STD circuit base with printed copper and female and male headers like this
    Attachment 22619

    These connectors have, the left-down one, 3 Vin connections only, 1 through the 110ohms resistor(2 220ohms in parallel...yes, just lazy to go out and buy one...); the other has on the lerft 4 MOSI connections, 3 MISO cons, and 3 3.3V cons (2 with 10K in the middle). On the right side 4 SCK cons and 2 GND cons.
    (I hope Im making myself clear) The CS's and DC's go directly to the teensy.

    I push the ino file, I connect the usb, and it works, but after a time, it gets white. I got to count for a minute, and then white, but discovered that disconnecting and connecting again it made it work again, but less time, like 30secs, then 12, and then wont put image, only white...
    USB disconnected, tested resistance and found a time-decreasing almost short (42ohms) between SCK and GND... as time passed and the teensy cooled they were again at high resistance, but Im not really sure how to know if this is allright, that would be a first question:

    1. How to test if I soldered correctly the teensy?, I give beforehand on the title, I did the headers's solder myself, some long female headers that are supposed to be for raspberry, that I tweaked to connect on the male side to the audio board, sitting on top of it...

    Click image for larger version. 

Name:	teensy.jpg 
Views:	44 
Size:	56.8 KB 
ID:	22620

    I found the SCK and GND were almost touching, had to cut the header, took out the pin, rasped the GND one, and the readings are now 1568K -1800K for all digital pins with GND . GND-3.3v is 6.89K. The photo shows the 13 SCK female header that was cut and changed.

    But this erratic behavior doesnt stop... If I connect the 9341 directly to the teensy, with a lot of female-male little testing cables, it works, but through the connectors I made, it sometimes shows image and sometimes no, more on the no side...

    I thought the problem is on the connectors I made, so made new ones, put GND, 3.3V and Vin alone, to the front, above the usb connector, and MISO, MOSI and SCK on another one, by the center, STD 11, 12, 13 setup.

    Im now using a long cable, almost 40CMS with female header to the male header of the 9341 screen, and male connections to the teensy. Im testing with the DEMOSAUCE.ino, and it behaves for about 40secs and then white, sometimes with intermittence... I disconnect, and sometimes gets image again... but I dont really change any specific... I tried disconnecting all the MISO-MOSI-SCK connector and the braking on the screen was different, it froze the image...

    Some other questions aligned with hipothesis have to do with using Vin as the source on the VCC connection, can I use 3.3v instead? the reset is going through a 10K, is it necessary? on the 9163 screen lib from sumotoy he recommended it, but I got esceptical...
    Can it be the lenght of the cable ? wouldnt it not even work at all? I have it sometimes showing almost 60 secs, 3 parts of the demosauce animations...

    I do conductivity tests between pins, on the connectors, on the screen and not a thing shows...

    Please Ideas, tutorials, guides for testing, STD procedures for good soldering, I dont know, Im quite frustrated...

    Thank you big community for reading until here... nice days!

  2. #2
    Junior Member
    Join Date
    Sep 2020


    Hello big community... as far as I've tried on the forum and outside, my guess is the length of the cable and its diameter 24awg get the problem done...
    particularly found these explanations relevant

    And the short and recent discussion I missed, as I've been trying to digest lots of topics these past weeks, is also good reference

    The topic is far beyond my experience, and knowledge, I'll report the things I find applying those recommendations,

    nice days!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts