Created August 31, 2025 © MIT

The Wio-pad

A peripheral (physical Key pad) that connects Wio modules to communicate either Wio node-to-node or Wio-to-phone (through Meshtastic).

IntermediateWork in progress4 days34

Things used in this project

Hardware components

Wio Tracker L1 Meshtastic Node

Li-Ion Battery 1000mAh

Grove Female Connectors

WS2812B-2020 Addressable RGB pixel LED

Tact Switch-TK-023-2 Pins 3*4 mm

5P Magnetic Spring Loaded Pogo Pin Male Female Connector Socket

5Pin Male Right Angle Berg Header Connector 6mm - 2.54mm Pitch

Software apps and online services

Meshtastic web flasher

Hand tools and fabrication machines

Soldering iron (generic)

Solder Paste, Rework

Multitool, Screwdriver

Vernier scale

Story

Story behind choosing this challenge

I am a final-year Bachelor of Technology student majoring in Internet of Things, and while studying ad hoc networks in wireless security networks, I discovered how mesh technology works. I wanted to make my own network to communicate over long distances without Wi-Fi, cellular networks, or even using a mobile telephone switching office or base station. It would run on its own, using nearby devices to form a mesh. I realized how useful this is in case of natural disasters, when ordinary infrastructure like telephone or Wi-Fi goes offline since they rely on central infrastructures. That’s when ad hoc or mesh technology comes into play. This technology amazed me a lot, so I made a minor project around it, which I also posted on Hackster as "LoRa Messenger 1.0".

my previous design for LoRa messanger using same tech

Communicating with a friend when other networks go offline is kind of interesting😁.

Abstract

The Wio L1 tracker device uses Meshtastic technology to communicate over a mesh network. Unlike cellular or Wi-Fi, these modules use the Nordic nRF52840 chip, which has built-in Bluetooth 5.0 to connect with smartphones. This allows a mesh to be created where the phone connects to the Wio device, and that Wio device connects to another Wio device located farther away. The peripheral

Wio Pad

Enables the Wio module to send text without relying on a cellphone. Using its compact QWERTY-style mini pad, it can send strings of text directly between Wio-to-Wio nodes.

Connecting through magnetic pogo connectors makes it special and portable, allowing rapid connection from the WioPad to the Wio Tracker L1

System Overview

The Wio-Pad consists of a Wio L1 Tracker module connected to a minimalistic keyboard peripheral via a Grove connector. The Wio Tracker, based on the Nordic nRF52840, runs on Meshtastic firmware to enable long-range, low-power communication over the LoRa SX1262

the diagram illustration show how mesh technology works over devices to devices without using existing infrastucture for communication

When a user types a message on the Wio Pad, the keystrokes are first captured by the keyboard circuit and transmitted to the Wio Tracker via UART or I²C through the Grove interface. The Wio Tracker then encodes the message and sends it over the LoRa mesh network to another Wio device.

LoRa Mesh

On the receiving end, the Wio device decodes the incoming message and forwards it to a connected smartphone via Bluetooth 5.0, where the text is seamlessly displayed in the Meshtastic app.

The Hardware Behind the Project

I chose to use an ATmega32 for the WioPad. The WioPad has a lot of tactile buttons and some LEDs, and wiring each button to its own digital pin felt a bit… noob. So I thought—why not use a budget MCU to make a proper peripheral? That’s when I decided to go with I²C (Inter-Integrated Circuit), much like how our computers talk to keyboards or mice over USB as part of the HMI. All the buttons are arranged in a matrix pattern, as shown below

Doing matrixification of switches

You can check out the full schematic file below to see how it all comes together.

The matrix I designed has 10 columns and 4 rows. The rows are connected to high signals on the MCU, and whenever a button is pressed, the corresponding column picks up that high signal. That’s the principle behind it—and it means this 40-button matrix can run using only 14 digital pins on the ATmega328, instead of wasting one pin per button. Kinda smart 🙂

There was one tactile switch left, so I decided to connect it directly to a digital pin and make it the ‘send’ button. To go with it, I added an acknowledgment LED that lights up whenever the button is pressed—basically telling you the message has been sent.

Since the WioPad is also able to send special characters, it needed a shift button. For that, I included a WS2812B LED that lights up whenever shift is pressed and held. Just for fun (and aesthetics), I went with the tiny WS2812B in the 2020 package. For now, it’s mostly for looks, but in future versions I plan to give it a real role—like showing notifications or acknowledgments in style

And after putting it all together, the circuit doesn’t just work—it actually looks pretty cool too

1 / 4 • fusion and kicad preview

Below is the schematic showing all the component values for this PCB. The ATmega328P chip is set up with its basic configuration: a 16 MHz crystal, a pull-up resistor, and a 100 nF DTR capacitor. In addition, there are a few more resistors and capacitors, an LED connected to a digital pin, and all the necessary pads for UART and I²C port

find whole schematic file below

Note: Since the Wio Tracker L1 already has a built-in battery management system for LiPo batteries, I didn’t include any battery-related circuitry in my design. After all, a peripheral isn’t really supposed to carry its own battery

Credit:Meshtastic

In my case, I’m using a 1.3-inch OLED display.

lets understand whats inside wio tracker l1

Credit : seeed studio

The WioPad uses the Grove connector’s VCC, GND, D0, and D1 pins as I²C pins, which—as mentioned—is fully supported by the Wio modules. On the Wio modules, we also have a switch and a joystick, which could be used later to add more functions, like toggling through the contact list.

Credit : Jessie219

As shown in the image, we’re using only 4 pins of the Grove connector: VCC, GND, D0 as SCL, and D1 as SDA

The Grove connectors[grove ecosystem] are then routed to pogo magnetic connectors, keeping everything neat and portable.

3D Files Preview

After fixing the pogo magnetic connectors to the enclosure, it will look like this.

All the attachments for the Wio Tracker L1 remain the same, as I’m not changing anything in the Wio Tracker itself. I simply made a peripheral—the WioPad—that connects to the Wio Tracker L1 through magnetic pogo connectors, fully compatible with the Grove ecosystem.

Here’s how it’s going to connect to the WioPad.

the upper case closure is for illustration not a part of design

Note: There are still some minor changes pending, but since the submission requires the final design, I’m submitting this version

Software for The Wio-pad

Schematics

Code

Code for Wio-pad

#include <Wire.h>
#include <Keypad.h>
#include <Adafruit_NeoPixel.h>

// Keypad configuration (your original setup)
const byte ROWS = 4;
const byte COLS = 10;

char keys[ROWS][COLS] = {
  {'1','2','3','4','5','6','7','8','9','0'},
  {'q','w','e','r','t','y','u','i','o','p'},
  {'a','s','d','f','g','h','j','k','l','!'},
  {'*','-','z','x','c','v','b','n','m',','}
};

byte rowPins[ROWS] = {12, 13, A0, A1};
byte colPins[COLS] = {2, 3, 4, 5, 6, 7, 8, 9, 10, 11};

// Keypad library instance
Keypad customKeypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// WS2812B LED setup
#define LED_PIN A3
#define NUM_LEDS 1
Adafruit_NeoPixel strip(NUM_LEDS, LED_PIN, NEO_GRB + NEO_KHZ800);

// Send button
const int send_pin = A2;
bool send_pin_state = false;

// Last key to send over I2C
char lastKey = 0;

void setup() {
  Wire.begin(8);               // I2C slave address
  Wire.onRequest(requestEvent);

  pinMode(send_pin, INPUT_PULLUP);

  strip.begin();
  strip.show();

  // Simple startup animation (red fade-in)
  for (int i = 0; i < 256; i += 5) {
    strip.setPixelColor(0, strip.Color(i, 0, 0));  // Red brightness increases
    strip.show();
    delay(10);
  }
  delay(500);

  strip.setPixelColor(0, 0);  // Turn off LED after animation
  strip.show();
}

void loop() {
  char customKey = customKeypad.getKey();

  // Detect send button press
  if (!digitalRead(send_pin) && !send_pin_state) {
    lastKey = '{';    // Special send indicator
    send_pin_state = true;
  }

  if (digitalRead(send_pin) && send_pin_state) {
    send_pin_state = false;
  }

  // Capture keypad keypress
  if (customKey) {
    lastKey = customKey;
  }

  delay(1);
}

// I2C request event: send the last key and reset it
void requestEvent() {
  Wire.write(lastKey);
  lastKey = 0;
}

Credits

vishal soni

10 projects • 12 followers

Engineer ,Electronic Enthusiast

The Wio-pad

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Story behind choosing this challenge

Abstract

System Overview

The Hardware Behind the Project

lets understand whats inside wio tracker l1

3D Files Preview

Software for The Wio-pad

Custom parts and enclosures

Wio tracker enclosure with pogo magnetic connector

Enclosure for The Wio-pad

Schematics

schmatic diagram

Layout diagram

The gerber file for pcb

Code

Code for Wio-pad

Credits

vishal soni

Comments

Embed the widget on your own site

The Wio-pad

The Wio-pad

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Story behind choosing this challenge

Abstract

System Overview

The Hardware Behind the Project

lets understand whats inside wio tracker l1

3D Files Preview

Software for The Wio-pad

Custom parts and enclosures

Wio tracker enclosure with pogo magnetic connector

Enclosure for The Wio-pad

Schematics

schmatic diagram

Layout diagram

The gerber file for pcb

Code

Code for Wio-pad

Credits

vishal soni

Comments

Related channels and tags