Maximizing the number of touchkeys

AN3236

12/15

DocID17613 Rev 3

4

Maximizing the number of touchkeys

The user can combine the touchkey matrix with single electrode touchkeys to maximize the

number of possible touchkeys. This gives a pure single touch interface.

In this configuration, single electrodes are added on each row and column of the touchkey

matrix as shown in Figure 7. There are two decoding cases:

•

if one channel is detected, the connected single electrode touchkey is touched

•

if two channels are detected, the touchkey corresponding to the intersection of the two

channels is touched.

In the case of multi-touches, it is impossible to discriminate which touchkeys are touched.

This solution is only adapted for applications where the user touches one key at a time.

Figure 7. Touchkey matrix with a single electrode on each channel