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