Utility libraries¶

BASE64 · CRC32 · SEVENTY-SIX DECLARATIONS · ONE USE

Two small libraries with a striking ratio between how often they are declared and how often they are used. One sits in seventy-six of the eighty platformio.ini files and occurs in exactly one source file; the other has a job you would not expect.

[!NOTE] Source. This page was verified against the firmware itself: MeshCore v1.16.0, commit 03b6ef4, 28 July 2026 — files src/helpers/BaseChatMesh.cpp, src/helpers/ui/GxEPDDisplay.h, src/helpers/ui/E213Display.h, src/helpers/ui/E290Display.h and the seventy-nine variants/*/platformio.ini.

How MeshCore calls this group¶

Unlike the sensors and the displays, these two do not sit behind an abstraction. They are called where they are needed, behind an #ifdef on a feature flag:

src/helpers/BaseChatMesh.cpp r.865-873

#ifdef MAX_GROUP_CHANNELS
#include <base64.hpp>

ChannelDetails* BaseChatMesh::addChannel(const char* name, const char* psk_base64) {
  if (num_channels < MAX_GROUP_CHANNELS) {
    auto dest = &channels[num_channels];

    memset(dest->channel.secret, 0, sizeof(dest->channel.secret));
    int len = decode_base64((unsigned char *) psk_base64, strlen(psk_base64), dest->channel.secret);

densaugeo/base64¶

Base64 encodes arbitrary bytes as readable text — four characters per three bytes, from an alphabet of sixty-four. The library by densaugeo is a minimal Arduino implementation: encoding, decoding, and working out the required buffer length, without dynamic memory.

This library is declared in seventy-six of the eighty platformio.ini files — more often than any other. In the source it is used in one place, in the code above: decoding a channel key supplied as text. A user entering #zwolle with a PSK gives that key in base64; this line turns it back into bytes.

The ratio of seventy-six declarations to one use is not a mistake, but it is typical of how the variant files came about: a variant is made by copying an existing one, and the lib_deps comes along.

bakercp/CRC32¶

CRC32 computes a thirty-two-bit check value over a sequence of bytes. The classic use is error detection during transmission or storage. MeshCore does not use it for that.

All three places where the library occurs are e-ink display drivers:

src/helpers/ui/GxEPDDisplay.h r.15
src/helpers/ui/E213Display.h r.8
src/helpers/ui/E290Display.h r.8

Each of the three keeps a CRC32 display_crc;. Refreshing an e-ink panel takes a second or more, is visible as flicker and wears the panel out. By keeping a check value over the content to be drawn, the driver can establish that the image has not changed and skip the refresh.

Fifteen variants declare the library — the e-ink variants and a number derived from them.

Overview¶

Library	Version	`.ini`	Source files	Used for
`densaugeo/base64`	`~1.4.0`	76	1	decoding a channel PSK
`bakercp/CRC32`	`^2.0.0`	15	3	skipping an unnecessary e-ink refresh

Sources¶

Translated from Dutch by Anthropic Claude