Using the front panel board

UM0756

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Doc ID 16031 Rev 1

4.1.8

RESTORE

When this key is touched the system restores the factory default values for volume, channel

and brightness (see Section 2.5).

4.2

Rotary encoder

The system has a free-running rotary encoder on the board. This encoder can be used to

increase/decrease the volume when the system is in the normal mode, or to

increase/decrease the brightness of the LED display when the system is in brightness

mode.

The encoder can be rotated clockwise or counter-clockwise to increase or decrease the

system parameters.

The free-running rotary encoder can be given countless rotations in any direction. This

encoder gives two square wave outputs which are phase-shifted from each other, and the

type of phase shift gives an indication of the direction of rotation. The number of pulses in

the square wave signal provides the number of rotations (Figure 11).

Figure 11.

Rotary encoder

In this system, the output of the rotary encoder is given to a dual D flip-flop to stabilize and

predefine the default level of the two signals. The output of the flip-flop is provided to the key

inputs of the LED316S device (see schematic in Section 6). Depending on the rotation of

the encoder the two key press interrupts follow the order.

Note:

The decoding of the rotary encoder using the STLED316S device saves the extra I/O of the

FP MCU, which would otherwise detect the sensor input.

Note:

The decoding of the rotary encoder can be done in parallel with the normal working of the

other keys, if these functions are included in the system. In the present system, the rotary

encoder is decoded along with the water level measurement, which is also connected at the

key inputs of the STLED316S device (see Section 4.3.1).