MSP430G2553

I purchased this module as part of a microcontroller kit, its an interesting little module as it has 16 buttons but with only 1 I/O line is required, an analog input. You connect this to your LaunchPad MSP430G2553 and read in the value.

The concept is straightforward  you use a resistor network as voltage dividers, and then let each button feed a different voltage to the analog pin. So by detecting the voltage you can tell which button has been pressed. You can only detect one button at a time

Here is the schematic of the module, hopefully you can see what I described earlier

You will have to wire Vcc of the module to 3.3v otherwise the readings will be incorrect

Code

I put in a slight delay to try and compensate for bounce on the key press which would result in multiple values returned

[codesyntax lang=”cpp”]

#define KEYPAD_PIN A5
 
// milliseconds to wait, to make sure key is pressed
#define TIME_TO_WAIT 200
 
void setup()
{
 Serial.begin(9600);
}

void loop() {
 // put your main code here, to run repeatedly:
 
 int reading1 = analogRead(KEYPAD_PIN);
 // waiting
 delay(TIME_TO_WAIT);
 // reading 2nd time - to make sure key is pressed
 int reading2 = analogRead(KEYPAD_PIN);
 if(reading2 <= 1000)
 {
 Serial.println(reading2);
 }
}

[/codesyntax]

Output

Pressing the keys from K0 to K16 outputted the following in the serial monitor (rough values)

0
61
125
190
253
316
380
447
510
576
641
702
765
831
896
960

So using a switch case you can use this module in your own examples, best practice would be to have a high and low value and check between the range

Links

AD Keypad 16 4×4 Accessory board matrix buttons controlled ADC