nipuna wickramasinghe

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8 years, 5 months ago.

Wiring a MPR 121 capacitive touch keypad to LPC 1768

Plz can someone provide the schematics to connect MPR 121 capacitive touch keypad to a LPC 1768

1 Answer

Oliver Broad
8 years, 5 months ago.

Looks like a fairly ordinary I2C device so try picking any MBED I2C port such as P27 SCL, P28 SDA and add 10K pull-up resistors from both pins to VOUT (3.3V).

Then connect MBED GND to keypad GND and MBED VOUT to keypad VCC, SDA to SDA, SCL to SCL.

You usually don't have to use "INT" if you read the keypad often enough.

Accepted Answer

will it work if I use 4.7k pull ups

posted by nipuna wickramasinghe 31 May 2016

Should do, I2C is pretty tolerant unless you are trying to go very fast or long distance.

This probably tells you more than you wanted to know about determining the resistors: http://www.ti.com/lit/an/slva689/slva689.pdf

posted by Oliver Broad 31 May 2016