Arduino HCMODU0188 User manual

Arduino Quick Start Guide and
Examples for
mLink Matrix 4x4 Keypad
(HCMODU0188)

Setting up your mLink module in 3 easy steps
Step 1: Connecting to your microcontroller
DEVICE
VDD
GND
SDA
SCL
Uno/Nano
3.3V/5V
GND
A4
A5
Pro Mini
3.3V/5V
GND
A4
A5
Pro Micro
3.3V/5V
GND
2
3
Mega
3.3V/5V
GND
20
21
Due
3.3V/5V
GND
20
21
Other microcontroller
3.3V/5V
GND
I2C SDA
I2C SCL
mlink modules can be connected to any microcontroller with an I2C (IIC) serial master
interface. The above example shows a mLink module connected to an Arduino Uno’s I2C
interface. It can be powered via a 5V or 3.3V supply (depending on the logic levels you
require the modules digital IO pins to operate at, and voltage requirements of any additional
mLink modules connected to the modules I2C output).
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Connecting multiple mLink modules
Each mLink module includes pullup resistors (10K), which are required for the SDA and SCL
data lines. This allows up to 5* mLink modules to be connected directly to an I2C master
without any additional hardware or modifications.
*note maximum number of modules will be dependent on data cable lengths and module
power requirements.
If more than 5 mLink modules are required to be connected to a single master interface then
the built-in 10K resistors will need to be removed from the additional modules.
The two 10K pullups can be removed from the I2C bus by breaking the tracks between the 3
pads shown in the diagram above. Should you need to reconnect the 10K pullups at a later
date this can be done by bridging the 3 pads with solder.
The mLink matrix 4x4 keypad comes with a preset I2C address of 0x55 (hex). When
connecting multiple modules of the same type each module's I2C address must be unique.
Therefore you must change the address of any additional modules to a unique address
(valid I2C addresses range between 0x08 and 0x77) before linking them together. Changing
a module's I2C address can be done via the module's I2C interface. For examples of how to
do this, see the Changing I2C address section within this document.
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Step 2) Installing the mLink Library
Adding the mLink library to your Arduino IDE can be done in the same way as any other
standard Arduino library:
First download the mLink.zip file from the software section of our support forum here:
https://hobbycomponents.com/mLink
Once downloaded, open up your Arduino IDE and go to Sketch->Include Library->Add .ZIP
Library.
In the file selection dialogue window that opens up, navigate to wherever you downloaded
the mLink .zip file and select it, then click the ‘Open’ button.
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Step 3) Including the mLink library in your sketch
Adding the mLink library to your sketch consists of 3 steps; Firstly, include the mLink header
file (mLink.h) at the top of your sketch, create an instance of the library, then finally initialise
the library inside the startup() function:
// Step 1: Include the mLink library
#include "mLink.h"
//Step 2: Create an instance of the library
mLink mLink ;
void setup ()
{
// Step 3: Initialise the library
mLink . init ();
}
void loop ()
{
}
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Quick Start Examples
Reading the last pressed key
The module will continually scan the keypad for keypress and will store the last (or current)
key to be pressed. Therefore obtaining the last key pressed is simply a case of reading the
modules key register.
Note that after the key register is read it will automatically be cleared (set to 0) even if a key
is still pressed. If you need to know if a key is currently pressed see the key pressed
example.
The following example will repeatedly read the key pressed register and will output a key (as
an ASCII value) to the serial monitor if a key has been pressed.
#include "mLink.h"
mLink mLink;
#define I2C_ADD 0x54
void setup()
{
mLink .init();
Serial .begin(9600)
}
void loop()
{
char key = mLink . read (I2C_ADD , KEYPAD_4X4_KEY); // Read the key status
if (key) // Has a key been pressed ?
{
Serial . print ( "Key: " ); // If so then output the key to the serial monitor
Serial . println (key);
}
}
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Reading the key pressed state
To determine if a key is currently pressed you can use the mLink libraries
Keypad_4x4_Key_Down(add) macro. If any of the keypad keys are currently pressed it will
return a ‘1’. If none of the keys are currently pressed it will return a ‘0’.
The following example gets the key pressed state and outputs it to the monitor window.
#include "mLink.h"
mLink mLink;
#define I2C_ADD 0x54
void setup()
{
mLink .init();
Serial .begin(9600)
}
void loop()
{
byte keyState = mLink . Keypad_4x4_Key_Down(I2C_ADD); // Read the key pressed status
if (keyState)
Serial . println ( "Key pressed !" );
}
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Changing the I2C address
To change the module's address you can use the libraries write() function.
The following example changes the module's I2C address from the default 0x55 to 0x56.
The new address will automatically be saved into non-volatile memory and so will retain the
new address even after power has been removed from the module.
Before the module's address can be changed, the address register must first be unlocked by
writing the byte value 0x55 followed by the byte value 0xAA to the register. The new address
must then be written within 100ms of sending the 0xAA byte otherwise the unlock process
will timeout and the process will then have to be restarted.
#include "mLink.h"
mLink mLink;
void setup()
{
mLink.init();
// Unlock the address register by writing 0x55 followed by 0xAA
mLink . write (0x55 , MLINK_ADD_REG , 0x55);
mLink . write (0x55 , MLINK_ADD_REG , 0xAA);
// Change the I2C address from 0x55 to 0x56
mLink . write (0x55 , MLINK_ADD_REG , 0x56);
}
void loop()
{
}
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Factory Reset
Should you wish to restore the module back to its factory default configuration, this can be
done by manually forcing a factory reset. All mLink modules include a set of pads labelled
clear:
Note, exact location of clear jumper may vary on your module
To perform a factory reset carefully short the two pads together with a piece of wire or with
something conductive such as a paperclip.
Whilst shorted, connect power to the module via the VCC and GND connections.
Wait a few seconds and then remove the short from the pads.
The module's settings, including its I2C address, should now be restored back to factory
defaults.
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DISCLAIMER
The mLink range is a series of modules intended for the hobbyist and educational markets.
Where every care has been taken to ensure the reliability and durability of this product it
should not be used in safety or reliability critical applications.
This document is provided "as is". Hobby Components Ltd makes no warranties, whether
express, implied or statutory, including, but not limited to, implied warranties of
merchantability and fitness for a particular purpose, accuracy or lack of negligence. Hobby
Components Ltd shall not, in any circumstances, be liable for any damages, including, but
not limited to, special, incidental or consequential damages for any reason whatsoever.
COPYRIGHT NOTICE
This manual, including content and artwork is copyright of Hobby Components Ltd and may
not be reproduced without written permission. If you paid for or received a copy of this
manual from a source other than Hobby Components Ltd, please contact us at
[email protected]
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