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Do not perform redundant reset on ST7789 displays

The `::init` method in the Adafruit ST7789 library is responsible to
initialize the device. This includes performing a reset, which can be
found in the Adafruit source for `Adafruit_SPITFT`.

Before this change, MeshCore performed its own ST7789 display reset
sequence, which consisted of three steps.

* Pull reset low
* Wait 10ms
* Pull reset high

Importantly, there was no fixed delay after pulling reset high. The
ST7789 driver requires a delay (T<sub>RT</sub>) of 5ms in Sleep In Mode
and 120ms in Sleep Out Mode before it will properly receive commands.
When `Adafruit_SPITFT` resets the device after MeshCore has already
reset it, the mandatory time may not have elapsed, leading to strange
behavior. In the author's case, this issue caused the initial
`fillScreen` to fail, such that the display showed an uninitialized
framebuffer.

This removes the MeshCore delay, leaving the responsibility of reset to
`Adafruit_SPITFT`, where they have the correct delays in place with
extra safety margin. The change was briefly tested by Josiah VanderZee
and Ben Zignego on a custom hardware build using an nRF52840 Dongle and
an Adafruit 4311 TFT display. The user button seemed to behave
strangely, but the display looked correct.
pull/2475/head
Josiah VanderZee 1 month ago
parent
commit
e56c1b3d58
No known key found for this signature in database GPG Key ID: C7BB8573A4ABC4B9
  1. 8
      src/helpers/ui/ST7789LCDDisplay.cpp

8
src/helpers/ui/ST7789LCDDisplay.cpp

@ -27,12 +27,6 @@ bool ST7789LCDDisplay::begin() {
pinMode(PIN_TFT_LEDA_CTL, OUTPUT);
digitalWrite(PIN_TFT_LEDA_CTL, HIGH);
}
if (PIN_TFT_RST != -1) {
pinMode(PIN_TFT_RST, OUTPUT);
digitalWrite(PIN_TFT_RST, LOW);
delay(10);
digitalWrite(PIN_TFT_RST, HIGH);
}
// Im not sure if this is just a t-deck problem or not, if your display is slow try this.
#if defined(LILYGO_TDECK) || defined(HELTEC_LORA_V4_TFT)
@ -166,4 +160,4 @@ uint16_t ST7789LCDDisplay::getTextWidth(const char* str) {
void ST7789LCDDisplay::endFrame() {
// display.display();
}
}

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