Shift register HC164 sensitivity issue

[Ritika Dhyawala]

I am controlling 5 shift registers (74HC164) from TI's cc3200 launchpad. I am clocking the data using GPIO pin and controlling LEDs though it. But my shift register is giving weird results. It gives output when i bring my hand near to it or a wire near to it (works 50% of time). Some times output LEDs go weird when touch the IC, like all LEDs will start glowing when only one should be glowing.
My power supply is sufficient(1A) for the no of LEDs i am running(21 LEDs, each drawing 10mA(3.v/330ohms) so 210mA). I tried putting decoupling cap of .1uF between Vcc and Gnd, but it did not work, Also i have put a 10nF between Clock and Ground. I have taken care of setup and hold time of HC164 in my code.
Is there anything i am missing here. I have connected Clock, Data and MR(active low) to cc3200's GPIO (3.3v)

 

[Harald Kapp]

Also i have put a 10nF between Clock and Ground

this capacitance may slew the edge of your clock too much. Use a smaller one, e.g. 100pF plus a series resistor of a few 100Ω to build a low pass filter for clock.

Also show us a schematic diagram of your circuit. The effect you observe can easily be achieved by open inputs to the CMOS chips.
Are the shift registers also powered from 3.3V or from 5V?

 

[Ritika Dhyawala]

My shift registers are powered from 3.3v (ground common with the controller)
I have tried with 100pF plus a series resistor of 100Ω but still it not working.

 

[Harald Kapp]

Also show us a schematic diagram of your circuit. The effect you observe can easily be achieved by open inputs to the CMOS chips.

 

[Ritika Dhyawala]

 

[BobK]

I can't see anything wrong with that unless the GPIO driving the A and B inputs or CLK is set to input sometimes.

Bob

 

[Harald Kapp]

I completely agree.

 

[Ritika Dhyawala]

Yes, the energia library in CC3200 was using the data(output pin) as analog pin, therefore it did not take it as output pin and it remained floating. Thanks for solving the problem.