Peripherals¶

BUZZER · LED · BUS EXPANDER · ACCELEROMETER

Four libraries drive whatever else may hang off a MeshCore board: a buzzer, an addressable LED, a bus expander that solves a shortage of pins, and an accelerometer. They have little to do with one another, beyond none of them being part of the measuring or the communication.

[!NOTE] Source. This page was verified against the firmware itself: MeshCore v1.16.0, commit 03b6ef4, 28 July 2026 — files platformio.ini, src/helpers/ui/buzzer.cpp, src/helpers/ui/GxEPDDisplay.cpp, variants/thinknode_m5/ and variants/wio_wm1110/platformio.ini.

How MeshCore calls this group¶

All four sit behind an #ifdef on a pin constant from the variant file. If the pin does not exist, the code does not exist:

src/helpers/ui/buzzer.cpp r.1-16

#include "Arduino.h"
#ifdef PIN_BUZZER
#include "buzzer.h"

void genericBuzzer::begin() {
//    Serial.print("DBG: Setting up buzzer on pin ");
//    Serial.println(PIN_BUZZER);
    #ifdef PIN_BUZZER_EN
      pinMode(PIN_BUZZER_EN, OUTPUT);
      digitalWrite(PIN_BUZZER_EN, HIGH);
    #endif

    quiet(false);
    pinMode(PIN_BUZZER, OUTPUT);
    digitalWrite(PIN_BUZZER, LOW); // need to pull low by default to avoid extreme power draw
}

end2endzone/NonBlockingRTTTL¶

RTTTL is the text format old Nokia phones stored their ringtones in: a name, a few default settings and then the notes as text. The ordinary Arduino implementations play such a melody using delay(), which stops the firmware for seconds at a time. NonBlockingRTTTL does it with a state machine that takes one step per pass through the main loop — so a MeshCore node can play a melody and keep receiving packets at the same time.

MeshCore wraps it in genericBuzzer (src/helpers/ui/buzzer.h and .cpp), which starts, interrupts and silences the melody. With seventeen variants this is the most common library in this group after the display libraries.

adafruit/Adafruit NeoPixel¶

NeoPixel is Adafruit's name for addressable LEDs of the WS2812 type and relatives: one data line, and three or four bytes of colour per LED, with a protocol accurate to the microsecond. The library handles that timing per platform.

Declared in three variants, among them lilygo_techo_card, heltec_mesh_solar and nibble_screen_connect. The library is additionally brought in by three Adafruit sensor libraries as a dependency for their example sketches; see ../dependencies.md.

maxpromer/PCA9557-arduino¶

The PCA9557 is an I²C bus expander: one chip on the I²C bus supplies eight extra inputs and outputs. On boards where the pins have run out, the reset and select lines of an e-ink display may hang off it, for example.

MeshCore uses it on the ThinkNode M5. The expander is created in the variant file and used by the display driver:

src/helpers/ui/GxEPDDisplay.cpp r.5-6

  #include <PCA9557.h>
  extern PCA9557 expander;

variants/thinknode_m5/ThinknodeM5Board.cpp r.3

PCA9557 expander (0x18, &Wire1);

Note that the expander hangs off Wire1, the board's second I²C bus. This is the only library in the repo without a version specification in lib_deps: the line reads just maxpromer/PCA9557-arduino, so PlatformIO takes whatever is newest at that moment.

adafruit/Adafruit LIS3DH¶

The LIS3DH is a three-axis accelerometer, usable to notice that a device has been picked up or moved. The library is declared in one variant:

variants/wio_wm1110/platformio.ini r.36

  adafruit/Adafruit LIS3DH @ ^1.2.4

No include of Adafruit_LIS3DH can be found in src/, examples/, variants/ or arch/. That observation is described in ../dependencies.md; no conclusion is drawn from it here.

Overview¶

Library	Version	Variants	Board
`end2endzone/NonBlockingRTTTL`	`^1.3.0`	17	all boards with `PIN_BUZZER`
`adafruit/Adafruit NeoPixel`	`^1.10.0` · `^1.12.3`	3	T-Echo Card, Heltec Mesh Solar, Nibble Screen Connect
`maxpromer/PCA9557-arduino`	none	1	ThinkNode M5
`adafruit/Adafruit LIS3DH`	`^1.2.4`	1	Wio WM1110

Sources¶

Translated from Dutch by Anthropic Claude