PSoC4000s & The SmartIO – Part 4

In the previous post I built a 3-bit counter that is clocked by the PWM.  In this example I will show you how to make the same design work with an external clock.  It seems like it would be cool to use the CapSense Button to provide the clock.  I will start by copying SmartIOCountUp to a new project called SmartIOCountUpExtClock.

First, I delete the clock and PWM.  Then add a new digital output pin (P20) that I can toggle from the CapSense handler and a digital Input pin (P21) to clock the SmartIO.  I add a wire between them on the female header on the board.

The next step is to modify the SmartIO.  I change data4 and data5 to bypass.  Then make gpio1 an input and then set the Clock to gpio1.  Here is what the new SmartIO configuration looks like:


And the schematic.


Assign the pins.


I need to update the main.c write the CapSense button to P20 to be a clock source for the SmartIO


After I program the board, I can “clock” my statemachine with CapSense Button2.  Cool.  Obviously this example is a bit contrived in that I am running a wire on the outside of the chip, but you could imagine that you might have a “real” example that uses an onboard clock source.

You can find this PSoC Creator workspace on github in the directory called “SmartIO”.  This project is called “SmartIOCountUpExtClock”.

Index Description
PSoC4000s & The SmartIO – Part 1 An introduction to the SmartIO and first project
PSoC4000s & CSX Mutual CapSense Buttons Part 1 Using mutual capacitance
PSoC4000s & CSX Mutual CapSense Buttons Part 2 Using the CapSense tuner
PSoC4000s & The SmartIO – Part 2 A 3 input XOR logic gate
PSoC4000s & The SmartIO – Part 3 A 3 bit up counter state machine
PSoC4000s & The SmartIO – Part 4 Using an external clock with the Smart IO
PSoC4000s & The SmartIO – Part 5 Triggering an interrupt