low-cost keyboard

Posted on Jul 6, 2012

If your application uses a relatively powerful microcontroller, you can use several free I/O pins or an unused input with an ADC to effect an easy keyboard connection. But, if the microcontroller in your system has too few free I/O pins and no on-chip ADC, you can be in trouble. However, if your system doesn`t require a high-performance keyboard, you can solve the problem by using the circuit in Figure 1.

I/O (output) assumes the state logic 1, VOUT. VC charges to logic 1 (VOUT) or to a voltage that RS and the other resistors determines. (You can set the output I/O to logic 1 by default. In this case, you can omit steps 1 and 2, and the routine becomes f

Leave Comment

characters left:

New Circuits



Popular Circuits

Stereo VU Meter
White LED Supply Driver II
Touch switching 12V Light
Simple Temperature Indicator
how to build an inverter
Modulated Light DX
RMS Reading Voltmeter
facelift for the 7MHz TRX
Quick-Charge Auto-Fire Flash Circuit
Using AC power without power transistor switching circuit a
Controllable integrator F007 schematic
Current leakage protection circuit