MPR121 - And other chip for more than 20 input

[gabrielstuff]

Hi,

We would like to use some mpr21 chip to handle more than 20 inputs. Looking at the datashit, we can use multiple mpr21 to do so, but we prefere to find an other chip that would allow us to directly sens more than 20 input.

What would be your recommandations ?

Thanks,

G

[reyes]

Hi G,

MPR121 is limited to 12 input per sensor without using multiplexing, I would rather recommend you to use a mcu based touch sensing, however, even TSI (Touch Sensing Interface) integrated in some NXP mcus are limited to 16 inputs, so I recommend you to use TSS (Touch Sensing Software) where you can enable some GPIOs as touch sensing inputs, for more details about how to use TSS in the NXP mcus, please take a look at the application note AN4637.

Or, another solution would be to use the MPR121 with multiplexed keys, this way it can support more pads (e.g. eight inputs can support up to 36 pads), so, when the number of keys exceed the available sensor inputs, multiplexing or logical combinations can be created, you can find a guideline about how to create multiplexed keys in section 4 of the Application Note AN3863.

Have a great day,
Jose

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