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Thread: Display_ili9341

  1. #26
    Since these pins will be actively driven, there is no need for such a small pull up resistor.. All it does is increase power consumption... I'm just getting started with the teensy (just bought it) so I can't test anything yet, but when I do low power designs I never use anything smaller than 100k unless the interface spec dictates it. It may seem insignificant but all these pull ups add up!

  2. #27
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    You are correct, there is no reason to use this low of a resistance for pullups with CMOS circuits. A 100K pullup is still a bit wasteful for battery powered designs, 1 M will also work. 100K with a 5v supply if driven low by the microcontroller uses 250 microwatts of power. 1M uses 25 microwatts of power. If one is trying to conserve battery power even more, change the code to use the internal pullup resistor in the microcontroller for the short period when it is needed during initialization, then reconfigure the GPIO for output when actually using the GPIO pin. This gets rid of the static wasted power of the pullup for the majority of the use of the device. (Typical designs only initialize once per power cycle) Designs that go to sleep, then wake up and re-initialize hardware can still use this technique, but the battery life is likely to be more dependent on the duty cycle of sleep time vs active time then.

  3. #28
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    I have a board I just got which is different than the ones shown here.

    Am I correct that doing the following will allow me to connect this directly to a teensy3.1 without needing a line converter AND be able to use the other pins to use the SDCard reader as well?

    Reason I ask is because it looks like there is already 2 regulators onboard with 1 being for the SDCard and the the other for the LCD.

    Click image for larger version. 

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  4. #29
    Senior Member PaulStoffregen's Avatar
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    I know this is probably a silly question, but have you tried asking the vendor who sold you this display? Yeah, I know it's probably a "no name" Chinese merchant that knows nothing about the product.... but still, maybe at least try asking? At the very least, it can be amusing to see if they even try.

    If you haven't already made the display work with Teensy, I highly recommend you at least get the graphics working first. The moment you touch it with your soldering iron, figuring out how to solve any problems becomes more complicated. At least get the display working first.

  5. #30
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    Quote Originally Posted by PaulStoffregen View Post
    I know this is probably a silly question, but have you tried asking the vendor who sold you this display? Yeah, I know it's probably a "no name" Chinese merchant that knows nothing about the product.... but still, maybe at least try asking? At the very least, it can be amusing to see if they even try.

    If you haven't already made the display work with Teensy, I highly recommend you at least get the graphics working first. The moment you touch it with your soldering iron, figuring out how to solve any problems becomes more complicated. At least get the display working first.
    Yup no-name chinese vendor lol.

    And I was able to get the graphics tests working using the ILI9341_t3 libraries with 0 modifications to the board. Well as far as the LCD goes. I'm still not sure if I should be able to use the SDCard over the same pins as the LCD or if I have to use the pins on the other side of the card.

    Thanks though for the reply.

  6. #31
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    These boards tend to keep the SPI lines of the SD card and display separate, but have a look at the traces and see if they connect, or better yet, use a multimeter to test for the connection.

    If not, you can always join the SPI busses together on your breadboard.

  7. #32
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    Quote Originally Posted by TheQuestor View Post
    Yup no-name chinese vendor lol.
    It'd be amusing to hear what they answer? Well, if they even try. That is, if they even have contact info?!

    not sure if I should be able to use the SDCard over the same pins as the LCD or if I have to use the pins on the other side of the card.
    With other similar versions, including the one we sell (which we get in bulk from similar Chinese vendors), the SD signals are totally separate from the LCD signals. You'll almost certainly have to connect to both sides.

  8. #33
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    I have the same display board. I could not find a schematic with google and the aliexpress vendor was unable to provide a schematic. The 2nd "regulator" is a transistor for backlight control.
    This is my version of the schematic:

    Click image for larger version. 

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    as pdf: https://www.dropbox.com/s/retud9ol1t...ma_v2.pdf?dl=0
    Last edited by HWGuy; 04-06-2017 at 06:10 PM.

  9. #34
    Senior Member PaulStoffregen's Avatar
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    Oh, that's interesting. On older displays, the 3 resistors seemed to be in series with the signals. Are they really just pullups now?

    If so, seems like it might work as-is, without having to desolder and replace the resistors.

  10. #35
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    yes only pull-ups. The display/sd card works without modifications. Vcc connected to 3.3V from the Teensy 3.1. And [LED] without resistor to 3.3V or a pwm pin. The backlight brightness is controllable with pwm.
    Last edited by HWGuy; 06-29-2015 at 10:12 PM.

  11. #36
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    yike I followed these directions:

    https://www.pjrc.com/store/display_ili9341.html

    ILI9341 Pin Teensy 3.1
    Standard Teensy 3.1
    Audio Board Notes
    VCC VIN VIN Power: 3.6 to 5.5 volts
    GND GND GND
    CS 10 21 Alternate Pins: 9, 15, 20, 21
    RESET +3.3V +3.3V
    D/C 9 20 Alternate Pins: 10, 15, 20, 21
    SDI (MOSI) 11 (DOUT) 7
    SCK 13 (SCK) 14
    LED VIN VIN Use 100 ohm resistor
    SDO (MISO) 12 (DIN) 12


    and connected the VCC to the Teensy3.1's VCC not the 3.3v. gulp. But it's been running non-stop for a few hours now and no magic smoke.

  12. #37
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    Quote Originally Posted by TheQuestor View Post
    and connected the VCC to the Teensy3.1's VCC not the 3.3v.
    This is also fine.

  13. #38
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    What are the default pins for the SDCard on the teensy3.1?

    LCD Teensy3.1
    SD_CS ??
    SD_MOSI ??
    SD_MISO ??
    SD_SCK ??
    F_CS ??

  14. #39
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    SD_CS: any free digital pin
    SD_MOSI: 11
    SD_MISO 12
    SD_SCK: 13

    F_CS: this is the chip select for the not populated flash memory chip

  15. #40
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    Thanks for the reply. You can share pins? I already have the LCD on pins 11/12/13. If this is the case can't I just run a bridge between the SD_ and LCD_ MISO/MOSI/SCK?

  16. #41
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    yes you have to share the pins. The Teensy 3.1 has only one SPI module. You can connect more than one device to the SPI bus (MOSI, MISO, SCK are part of the SPI bus). The active device on the SPI bus is selected trough the *_CS pin (chip select or slave select). When SD_CS is low, the Teensy 3.1 communicates to the sd card, with CS (from the display) low the Teensy communicates with the display.

    https://en.wikipedia.org/wiki/Serial..._Interface_Bus

    If this is the case can't I just run a bridge between the SD_ and LCD_ MISO/MOSI/SCK?
    yes
    Last edited by HWGuy; 06-30-2015 at 01:09 AM.

  17. #42
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    Well that makes things a tad more simple. So only the signal (cs) needs to be unique? I have done a TON of work a while back with Addressable LEDS + WIFI + SD + NMEA GPS and I was so out of pins, but now it makes a lot more sense. It's kind of like the I2C bus on my Pixhawk and APM flight controllers it seems. I also have played with GY-80 IMU which allows all the sensors to use the same pins and just looks to different addresses for each on the bus.

    Thanks. Gunna plug back in the soldering iron and get this badboy working

  18. #43
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    Quote Originally Posted by TheQuestor View Post
    So only the signal (cs) needs to be unique?
    exactly.

    SPI is much faster than I2C.

  19. #44
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    Quote Originally Posted by HWGuy View Post
    The Teensy 3.1 has only one SPI module.
    Is this true? I've been wondering lately and found a reference in the programmers guide that there are two SPI modules SPI0 and SPI1. But the PJRC website and the linked data sheet indicate only one.

    I compared the T3.0 and its documentation all indicates one SPI port but the T3.1 programmers Guide in section 3.9.3.1 has this to say:
    This device contains two SPI modules

    and there's a whole lot more in the manual so I was thinking there might be 2 modules but not a library to support them.

    Anyone know for sure?

    Cheers

  20. #45
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    This is an error in the Freescale doc. The Teensy 3.1/MK20DX256VLH7 has only one SPI module.

    https://forum.pjrc.com/threads/28851...Teensy-3-1-NOT

  21. #46
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    'tis a bummer...

  22. #47
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by HWGuy View Post
    SD_CS: any free digital pin
    Any digital pin is ok. Most examples use pin 4. Some use pin 10. Use those if you want out-of-the-box compatibility with the widely published examples. If not, changing one number in the sketch is pretty easy.

    F_CS: this is the chip select for the not populated flash memory chip
    Pin 6 is recommended. If you use the SerialFlash library, it's currently hard-coded for pin 6. Future versions will likely be configurable, like SD.

  23. #48
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    I am new at electronics.
    however i just got a Tseensy USB board 3.2with the : ILI9341 screen.
    boards 3.1 are out od stock ;(
    as i couldn't find specific wiring to the 3.2 board.
    i was going to try :
    https://www.pjrc.com/store/display_ili9341.html .

    but then i saw the Caution message: about the voltage issues.
    anyone has a wiring diagram to suggest.
    Last edited by lyase; 12-01-2015 at 05:46 PM.

  24. #49
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    Quote Originally Posted by lyase View Post
    I am new at electronics.
    however i just got a Tseensy USB board 3.2with the : ILI9341 screen.
    as i couldn't find specific wiring to the 3.2 board.
    i was going to try :
    https://www.pjrc.com/store/display_ili9341.html .
    but then i saw the Caution message: about the voltage issues.
    anyone has a wiring diagram to suggest.
    The 3.1/3.2 are the exact same as far as wiring [and pretty much everything else] goes and has 3.3v CS, D/C, SDI, SCK which is why it says to USE a 3.1 (or higher) and not a 2.0 which was 5v

  25. #50
    Never having worked with smd components before, how do you substitute resistors?

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