App Inventor ESP32 Keypad 4x4

Send message from 4×4 keypad with ESP32 to smartphone via bluetooth

10-04-22 1796

The ESP32 is a powerful, low-cost microcontroller that includes built-in Bluetooth capabilities. This makes it well-suited for use in projects that involve wireless communication, such as a project that connects to a smartphone over Bluetooth.

To create a project that connects to a smartphone over Bluetooth using the ESP32, you will need to do the following:

Write code for the ESP32 that configures it as a Bluetooth peripheral and advertises itself to nearby devices.
Write code for the smartphone that scans for nearby Bluetooth devices and connects to the ESP32.
Once connected, the smartphone can send and receive data with the ESP32, allowing you to control or receive data from the ESP32 via the smartphone.

There are several libraries available for the ESP32 that make it easy to configure and control its Bluetooth capabilities, such as Espressif’s ESP32 BLE Python library. These libraries provide APIs for configuring the ESP32 as a Bluetooth peripheral, advertising itself, and managing connections with nearby devices.

Purpose of tutorial:

In this tutorial we will see how to send a message from the ESP32 card to the smarthpone via bluetooth using the matrix keypad. This is why we will create two programs: a mobile application with App Inventor for the smartphone and a program for the ESP32 card.

Keypad operation and ESP32:

Necessary components

ESP32 Card

An ESP32 card is a development board or module that is based on the ESP32 microcontroller developed by Espressif. It typically includes the ESP32 chip, as well as a number of peripheral components, such as RAM, flash memory, power management, and input/output (I/O) pins. ESP32 cards can come in a variety of form factors, including the ESP32-DevKitC, ESP32-WROVER, ESP32-PICO-D4 and more.

ESP32 card can be programmed using various programming languages such as C, C++, Python and MicroPython. The ESP32 has a built-in support for the Arduino IDE which makes it easy to program and debug.

4×4 keypad

A 4×4 keypad is a type of input device that consists of a grid of 4 rows and 4 columns of buttons. It is often used as a simple, low-cost way to add numerical input to a project, such as an access control system or calculator.

The buttons on the keypad are typically labeled with the digits 0-9, as well as a few additional characters such as * and #. Each button is connected to a pin on the keypad’s circuit board, and the pins are connected to a microcontroller or other electronic device.

connecting wires

Wires are used to transmit electrical signals and power to various components such as motors, sensors, and microcontrollers. It’s important to properly route and secure the wires to prevent tangles and damage. There are several methods for doing this, including using cable ties, clamps, and wire looms. It’s also a good idea to use different colors or labeling to identify the different wires and their functions. When connecting wires in a robot, it’s important to follow proper safety procedures, such as using the correct wire stripper and connectors, and wearing protective equipment such as gloves and safety glasses.

test plate

A test plate is a type of device used in robotics to test the functionality and performance of various components or systems. It is typically a physical platform or structure that is designed to hold and support various test items or devices, such as sensors, actuators, motors, or other types of mechanical or electrical components. Test plates can be used to simulate different environments or conditions, such as temperature, humidity, vibration, or other factors, in order to evaluate the performance of the components or systems being tested. They can also be used to perform a variety of diagnostic or diagnostic tests, such as stress testing, endurance testing, or other types of evaluations.

Assemby:

We connect the 8 outputs of the keyboard to the 8 pins of the ESP32 card following this order: D2, D4, D5, D18, D19, D16, D15 and D23.

Micropython program

Here are the programs that connect the ESP32 board to the smartphone and send a message by bluetooth using the 4×4 matrix keypad.

boot.py

from machine import Pin
from esp_ble_uart import *
from time import sleep
import utime
import machine
import time

nom = 'ESP32-ble-uart-gcworks'
UUID_UART = '6E400001-B5A3-F393-E0A9-E50E24DCCA9E'
UUID_TX = '6E400003-B5A3-F393-E0A9-E50E24DCCA9E'
UUID_RX = '6E400002-B5A3-F393-E0A9-E50E24DCCA9E'
val_rx = "12"

uart = Bleuart(nom, UUID_UART, UUID_TX, UUID_RX)
uart.close()

WIDTH  = 128                                            
HEIGHT = 64                                             

# CONSTANTS
KEY_UP   = const(0)
KEY_DOWN = const(1)

keys = [['1', '2', '3', 'A'], ['4', '5', '6', 'B'], ['7', '8', '9', 'C'], ['*', '0', '#', 'D']]

# Pin names for Pico
cols = [19,16,15,23]
rows = [2,4,5,18]

# set pins for rows as outputs
row_pins = [Pin(pin_name, mode=Pin.OUT) for pin_name in rows]

# set pins for cols as inputs
col_pins = [Pin(pin_name, mode=Pin.IN, pull=Pin.PULL_DOWN) for pin_name in cols]

def init():
    for row in range(0,4):
        for col in range(0,4):
            row_pins[row].value(0)

def scan(row, col):
    """ scan the keypad """

    # set the current column to high
    row_pins[row].value(1)
    key = None

    # check for keypressed events
    if col_pins[col].value() == KEY_DOWN:
        key = KEY_DOWN
    if col_pins[col].value() == KEY_UP:
        key = KEY_UP
    row_pins[row].value(0)

    # return the key state
    return key

print("starting")

def rcp_rx():
    global val_rx
    if uart.any():
        while uart.any():
          val_rx = uart.read().decode().strip()
          print('sur rx: ', val_rx)               # Interruption : affichage donn闁肩厧宕榮 re闁煎墽鎯甧s

def env_tx(val_tx):
    uart.write(str(val_tx) + '\n')
    print("tx", val_tx)

# set all the columns to low
init()
message=""
while True:
    uart.irq(handler=rcp_rx)
    for row in range(4):
        for col in range(4):
            key = scan(row, col)
            if key == KEY_DOWN:
                print("Key Pressed", keys[row][col])
                message=message+keys[row][col]
                env_tx(message) # sending the character associated with the press key to smartphone
                last_key_press = keys[row][col]
                time.sleep_ms(1000)

from machine import Pin

from esp_ble_uart import *

from time import sleep

import utime

import machine

import time

nom = 'ESP32-ble-uart-gcworks'

UUID_UART = '6E400001-B5A3-F393-E0A9-E50E24DCCA9E'

UUID_TX = '6E400003-B5A3-F393-E0A9-E50E24DCCA9E'

UUID_RX = '6E400002-B5A3-F393-E0A9-E50E24DCCA9E'

val_rx = "12"

uart = Bleuart(nom, UUID_UART, UUID_TX, UUID_RX)

uart.close()

WIDTH = 128

HEIGHT = 64

# CONSTANTS

KEY_UP = const(0)

KEY_DOWN = const(1)

keys = [['1', '2', '3', 'A'], ['4', '5', '6', 'B'], ['7', '8', '9', 'C'], ['*', '0', '#', 'D']]

# Pin names for Pico

cols = [19,16,15,23]

rows = [2,4,5,18]

# set pins for rows as outputs

row_pins = [Pin(pin_name, mode=Pin.OUT) for pin_name in rows]

# set pins for cols as inputs

col_pins = [Pin(pin_name, mode=Pin.IN, pull=Pin.PULL_DOWN) for pin_name in cols]

def init():

for row in range(0,4):

for col in range(0,4):

row_pins[row].value(0)

def scan(row, col):

""" scan the keypad """

# set the current column to high

row_pins[row].value(1)

key = None

# check for keypressed events

if col_pins[col].value() == KEY_DOWN:

key = KEY_DOWN

if col_pins[col].value() == KEY_UP:

key = KEY_UP

row_pins[row].value(0)

# return the key state

return key

print("starting")

def rcp_rx():

global val_rx

if uart.any():

while uart.any():

val_rx = uart.read().decode().strip()

print('sur rx: ', val_rx) # Interruption : affichage donn闁肩厧宕榮 re闁煎墽鎯甧s

def env_tx(val_tx):

uart.write(str(val_tx) + '\n')

print("tx", val_tx)

# set all the columns to low

init()

message=""

while True:

uart.irq(handler=rcp_rx)

for row in range(4):

for col in range(4):

key = scan(row, col)

if key == KEY_DOWN:

print("Key Pressed", keys[row][col])

message=message+keys[row][col]

env_tx(message) # sending the character associated with the press key to smartphone

last_key_press = keys[row][col]

time.sleep_ms(1000)

esp_ble_uart.py

from micropython import const
import struct
import bluetooth

# Advertising payloads are repeated packets of the following form:
#   1 byte data length (N + 1)
#   1 byte type (see constants below)
#   N bytes type-specific data

_ADV_TYPE_FLAGS = const(0x01)
_ADV_TYPE_NAME = const(0x09)
_ADV_TYPE_UUID16_COMPLETE = const(0x3)
_ADV_TYPE_UUID32_COMPLETE = const(0x5)
_ADV_TYPE_UUID128_COMPLETE = const(0x7)
_ADV_TYPE_UUID16_MORE = const(0x2)
_ADV_TYPE_UUID32_MORE = const(0x4)
_ADV_TYPE_UUID128_MORE = const(0x6)
_ADV_TYPE_APPEARANCE = const(0x19)

_IRQ_CENTRAL_CONNECT = const(1 << 0)
_IRQ_CENTRAL_DISCONNECT = const(1 << 1)
_IRQ_GATTS_WRITE = const(1 << 2)

# org.bluetooth.characteristic.gap.appearance.xml
_ADV_APPEARANCE_GENERIC_COMPUTER = const(128)

# Generate a payload to be passed to gap_advertise(adv_data=...).
def advertising_payload(limited_disc=False, br_edr=False, name=None, services=None, appearance=0):
    payload = bytearray()

    def _append(adv_type, value):
        nonlocal payload
        payload += struct.pack('BB', len(value) + 1, adv_type) + value

    _append(_ADV_TYPE_FLAGS, struct.pack('B', (0x01 if limited_disc else 0x02) + (0x00 if br_edr else 0x04)))

    if name:
        _append(_ADV_TYPE_NAME, name)

    if services:
        for uuid in services:
            b = bytes(uuid)
            if len(b) == 2:
                _append(_ADV_TYPE_UUID16_COMPLETE, b)
            elif len(b) == 4:
                _append(_ADV_TYPE_UUID32_COMPLETE, b)
            elif len(b) == 16:
                _append(_ADV_TYPE_UUID128_COMPLETE, b)

    # See org.bluetooth.characteristic.gap.appearance.xml
    _append(_ADV_TYPE_APPEARANCE, struct.pack('<h', appearance))

    return payload

def decode_field(payload, adv_type):
    i = 0
    result = []
    while i + 1 < len(payload):
        if payload[i + 1] == adv_type:
            result.append(payload[i + 2:i + payload[i] + 1])
        i += 1 + payload[i]
    return result

def decode_name(payload):
    n = decode_field(payload, _ADV_TYPE_NAME)
    return str(n[0], 'utf-8') if n else ''

def decode_services(payload):
    services = []
    for u in decode_field(payload, _ADV_TYPE_UUID16_COMPLETE):
        services.append(bluetooth.UUID(struct.unpack('<h', u)[0]))
    for u in decode_field(payload, _ADV_TYPE_UUID32_COMPLETE):
        services.append(bluetooth.UUID(struct.unpack('<d', u)[0]))
    for u in decode_field(payload, _ADV_TYPE_UUID128_COMPLETE):
        services.append(bluetooth.UUID(u))
    return services

class Bleuart:
    def __init__(self, name, UUID_UART, UUID_TX, UUID_RX, rxbuf=100):

        _UART_UUID = bluetooth.UUID(UUID_UART,)
        _UART_TX = (bluetooth.UUID(UUID_TX), bluetooth.FLAG_NOTIFY,)
        _UART_RX = (bluetooth.UUID(UUID_RX), bluetooth.FLAG_WRITE,)
        _UART_SERVICE = (_UART_UUID, (_UART_TX, _UART_RX,),)

        self._ble = bluetooth.BLE()
        self._ble.active(True)
        self._ble.irq(handler=self._irq)
        ((self._tx_handle, self._rx_handle,),) = self._ble.gatts_register_services((_UART_SERVICE,))
        # Increase the size of the rx buffer and enable append mode.
        self._ble.gatts_set_buffer(self._rx_handle, rxbuf, True)
        self._connections = set()
        self._rx_buffer = bytearray()
        self._handler = None
        # Optionally add services=[_UART_UUID], but this is likely to make the payload too large.
        self._payload = advertising_payload(name=name, appearance=_ADV_APPEARANCE_GENERIC_COMPUTER)
        self._advertise()

    def irq(self, handler):
        self._handler = handler

    def _irq(self, event, data):
        # Track connections so we can send notifications.
        if event == _IRQ_CENTRAL_CONNECT:
            conn_handle, _, _, = data
            self._connections.add(conn_handle)
        elif event == _IRQ_CENTRAL_DISCONNECT:
            conn_handle, _, _, = data
            if conn_handle in self._connections:
                self._connections.remove(conn_handle)
            # Start advertising again to allow a new connection.
            self._advertise()
        elif event == _IRQ_GATTS_WRITE:
            conn_handle, value_handle, = data
            if conn_handle in self._connections and value_handle == self._rx_handle:
                self._rx_buffer += self._ble.gatts_read(self._rx_handle)
                if self._handler:
                    self._handler()

    def any(self):
        return len(self._rx_buffer)

    def read(self, sz=None):
        if not sz:
            sz = len(self._rx_buffer)
        result = self._rx_buffer[0:sz]
        self._rx_buffer = self._rx_buffer[sz:]
        return result

    def write(self, data):
        for conn_handle in self._connections:
            self._ble.gatts_notify(conn_handle, self._tx_handle, data)

    def close(self):
        for conn_handle in self._connections:
            self._ble.gap_disconnect(conn_handle)
        self._connections.clear()

    def _advertise(self, interval_us=500000):
        self._ble.gap_advertise(interval_us, adv_data=self._payload)

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from micropython import const

import struct

import bluetooth

# Advertising payloads are repeated packets of the following form:

# 1 byte data length (N + 1)

# 1 byte type (see constants below)

# N bytes type-specific data

_ADV_TYPE_FLAGS = const(0x01)

_ADV_TYPE_NAME = const(0x09)

_ADV_TYPE_UUID16_COMPLETE = const(0x3)

_ADV_TYPE_UUID32_COMPLETE = const(0x5)

_ADV_TYPE_UUID128_COMPLETE = const(0x7)

_ADV_TYPE_UUID16_MORE = const(0x2)

_ADV_TYPE_UUID32_MORE = const(0x4)

_ADV_TYPE_UUID128_MORE = const(0x6)

_ADV_TYPE_APPEARANCE = const(0x19)

_IRQ_CENTRAL_CONNECT = const(1 << 0)

_IRQ_CENTRAL_DISCONNECT = const(1 << 1)

_IRQ_GATTS_WRITE = const(1 << 2)

# org.bluetooth.characteristic.gap.appearance.xml

_ADV_APPEARANCE_GENERIC_COMPUTER = const(128)

# Generate a payload to be passed to gap_advertise(adv_data=...).

def advertising_payload(limited_disc=False, br_edr=False, name=None, services=None, appearance=0):

payload = bytearray()

def _append(adv_type, value):

nonlocal payload

payload += struct.pack('BB', len(value) + 1, adv_type) + value

_append(_ADV_TYPE_FLAGS, struct.pack('B', (0x01 if limited_disc else 0x02) + (0x00 if br_edr else 0x04)))

if name:

_append(_ADV_TYPE_NAME, name)

if services:

for uuid in services:

b = bytes(uuid)

if len(b) == 2:

_append(_ADV_TYPE_UUID16_COMPLETE, b)

elif len(b) == 4:

_append(_ADV_TYPE_UUID32_COMPLETE, b)

elif len(b) == 16:

_append(_ADV_TYPE_UUID128_COMPLETE, b)

# See org.bluetooth.characteristic.gap.appearance.xml

_append(_ADV_TYPE_APPEARANCE, struct.pack('<h', appearance))

return payload

def decode_field(payload, adv_type):

i = 0

result = []

while i + 1 < len(payload):

if payload[i + 1] == adv_type:

result.append(payload[i + 2:i + payload[i] + 1])

i += 1 + payload[i]

return result

def decode_name(payload):

n = decode_field(payload, _ADV_TYPE_NAME)

return str(n[0], 'utf-8') if n else ''

def decode_services(payload):

services = []

for u in decode_field(payload, _ADV_TYPE_UUID16_COMPLETE):

services.append(bluetooth.UUID(struct.unpack('<h', u)[0]))

for u in decode_field(payload, _ADV_TYPE_UUID32_COMPLETE):

services.append(bluetooth.UUID(struct.unpack('<d', u)[0]))

for u in decode_field(payload, _ADV_TYPE_UUID128_COMPLETE):

services.append(bluetooth.UUID(u))

return services

class Bleuart:

def __init__(self, name, UUID_UART, UUID_TX, UUID_RX, rxbuf=100):

_UART_UUID = bluetooth.UUID(UUID_UART,)

_UART_TX = (bluetooth.UUID(UUID_TX), bluetooth.FLAG_NOTIFY,)

_UART_RX = (bluetooth.UUID(UUID_RX), bluetooth.FLAG_WRITE,)

_UART_SERVICE = (_UART_UUID, (_UART_TX, _UART_RX,),)

self._ble = bluetooth.BLE()

self._ble.active(True)

self._ble.irq(handler=self._irq)

((self._tx_handle, self._rx_handle,),) = self._ble.gatts_register_services((_UART_SERVICE,))

# Increase the size of the rx buffer and enable append mode.

self._ble.gatts_set_buffer(self._rx_handle, rxbuf, True)

self._connections = set()

self._rx_buffer = bytearray()

self._handler = None

# Optionally add services=[_UART_UUID], but this is likely to make the payload too large.

self._payload = advertising_payload(name=name, appearance=_ADV_APPEARANCE_GENERIC_COMPUTER)

self._advertise()

def irq(self, handler):

self._handler = handler

def _irq(self, event, data):

# Track connections so we can send notifications.

if event == _IRQ_CENTRAL_CONNECT:

conn_handle, _, _, = data

self._connections.add(conn_handle)

elif event == _IRQ_CENTRAL_DISCONNECT:

conn_handle, _, _, = data

if conn_handle in self._connections:

self._connections.remove(conn_handle)

# Start advertising again to allow a new connection.

self._advertise()

elif event == _IRQ_GATTS_WRITE:

conn_handle, value_handle, = data

if conn_handle in self._connections and value_handle == self._rx_handle:

self._rx_buffer += self._ble.gatts_read(self._rx_handle)

if self._handler:

self._handler()

def any(self):

return len(self._rx_buffer)

def read(self, sz=None):

if not sz:

sz = len(self._rx_buffer)

result = self._rx_buffer[0:sz]

self._rx_buffer = self._rx_buffer[sz:]

return result

def write(self, data):

for conn_handle in self._connections:

self._ble.gatts_notify(conn_handle, self._tx_handle, data)

def close(self):

for conn_handle in self._connections:

self._ble.gap_disconnect(conn_handle)

self._connections.clear()

def _advertise(self, interval_us=500000):

self._ble.gap_advertise(interval_us, adv_data=self._payload)

Creating the application with App Inventor:

We will create a mobile application named ‘esp32_clavier’ with App Inventor which allows to receive a message from the ESP32 card.

We therefore suggest that you create the design of the application, with the following visual:

Programming with App Inventor

To program the application, App Inventor offers us to use the Blocks space which allows you to create a program in the form of a block diagram. Very easy to use but requires some programming logic.

Here is the program of the application made in the Blocks space of the App Inventor:

Download project Download apk file

You can also see

View location data sent by NEO-M6 GPS using ESP32 board

22-02-23

Obstacle avoiding robot using ESP32

10-02-23

1 commentaire

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