Odd behaviour joy-it ST7735

Other Hardware Displays
1

Hello,
I'm using a Joy-it ST7735 greentab 1.8" TFT display with an Ardiuno Uno.
Everything works fine as long as it is connected to my 'programming' laptop.
If I connect the usb cable to another usb power supply the screen turns blank and shows nothing.

I connected the display in this way:
#define TFT_RST 8 // Blw Reset line for TFT (or connect to +5V)
#define TFT_CS 9 // Prs
#define TFT_DC 10 // Grn
// MOSI` 11 Or
// SCL 13 Gl
Adafruit_ST7735 tft = Adafruit_ST7735(TFT_CS, TFT_DC, TFT_RST);

And initiate is in this way:
tft.initR(INITR_GREENTAB); // initialize a ST7735S chip, green tab
tft.fillScreen(ST7735_BLACK);
tft.setTextWrap(false);
tft.setRotation(3); // rotates the display 270 gr. resolution 160 x128 pixels
Any suggestions. Thanks

2

Like many folks here, I suspect, I have accumulated quite a few USB power supplies. All of those that came with a phone or tablet have been fine, some of the others - not so much. See if you can find a better one.

3

Thanks Wildbill,
In my project I will use a stand alone ATmega 328 processor, so it not so much the USB power supply, but the need to be connected to the computer on which the Arduino program is on.
If I connect the UNO to my other laptop the display remains blank too.

4

Problem solved.
My 'programming' laptop delivers a quite low USB tension of 4.2 volts. On this the display works fine.
My other USB supplies deliver a neat 5 volts, and the display doesn't like that. So I reduced the tension on my stand alone board to 4.2 v and now it works.

5

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