Result

To use MTanalogButtons, I recommend running the apprenticeship program. This is mainly to generate the thresholds table easily. And this program offers a program that looks like this.

Of course, the thresholds depend on the assembly and you have to update them for it to work. Thresholds depend on the value exact resistances but also the card power supply.

Complete program example

// You must give the pin for analog reading
const uint8_t PIN = A5; // Change A5 to A0..A7 depending on the case
//
// You must choose the voltage reference to use for the conversion
// DEFAULT: for Vcc
// INTERNAL: 1.1V for Nano/Uno
// INTERNAL1V1: 1.1V for Mega
// INTERNAL2V56: 2.56V for Mega
// EXTERNAL: to use AREF
#define REFERENCE INTERNAL
//
// You must give the console transfer rate
#define BAUDS 115200 // 115200 recommended, but you can put 9600
// Don't forget to set the console to 115200 bauds

// This program tests the reading of the set of buttons with MTanalogButtons

#include  // V1.1.1 See http://arduino.dansetrad.fr/en/MTobjects

const word THRESHOLDS_TABLE[] = {982, 922, 880, 840, 797, 754, 710, 665, 619, 572, 522, 471, 421, 369, 316, 260, 203, 145, 87, 28, 0}; // Comparison threshold values

void press(byte key)
{
  Serial.print("Key number ");
  Serial.print(key);
  Serial.print(" just pressed ");
}
void release(void)
{
  Serial.println("and released");
}
MTanalogButtons Keypad(PIN, THRESHOLDS_TABLE, press, release);

void setup()
{
  Serial.begin(115200); // Also set the console to 115200 baud!
  analogReference(INTERNAL);
  Serial.println("Press keys");
}

void loop(){}