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PSoC 5, 3 & 1 MCU

New Contributor


I made a Custom Board with Character LCD Connected. 

Iam using Port 2[0:6] for Display output.

Iam using Port 1 for Programming (P1:0, P1:1, P1:3, P1:4, XRES Pin 10, 5V, GND)

The Problem is, when i Powerup everything, i have to connect the Miniprog to get the LCD output work.

Otherwise the LCD is only showing black Dashes.

After Miniprog is connected and the LCD is working i can disconnect the Miniprog and it will work normally.

I think it has to do something with the XRES Line at the startup sequence.

My Program:


int main()

CyGlobalIntEnable; // Enable global interrupts.

LCD_Position(0u, 0u);


Can Anyone help me ?

3 Replies
Contributor II


From your description, this is not a software issue.  It's a hardware issue.

I suspect the PSoC target is not coming out of RESET state on its own.  When connecting Mimiprog, Miniprog toggles XRES thus resetting target.  And/Or, Miniprog is providing power to target just enough to get it running and you have a powering design issue.

To test the RESET issue:
- power up your pcb
- momentarily touch a wire from XRES to Ground
If PSoC starts working this is the issue.
If PSoC doesn't start working, next momentarily touch a wire from XRES Vddd.
PSoC has now been reset.

As another test, you could connect a pull-up resistor (anything from 4.7k to 20k) from XRES to Vddd and see if pcb will come out of RESET state.

If the power supply is the issue, we'd need to see your schematic (pdf or screenshot would be fine).

New Contributor

Hello Bibi,


thanks to your Reply,

so when i touch XRES to GND Display Turns good.

I had this Problem before on Protopying Kit from PSOC5 where the Display was on another Port.

How to avoid this, to not touch GND with Xres ?

Is this a Powerup Delay Problem ?

I put a Screenshot of my Schematic.

Maybe a soldering Issue ?

Contributor II

Hi KesKina.

Thank you for providing schematic image.
I see an issue with schematic power connections.

Vccd - there are 2 Vccd pins to connect together.  I think your schematic has done this.  However, Vccd should not be connected to Vcca.  Vccd and Vcca are regulator outputs that need independent capacitors.  Disconnect Vcca from Vccd and add another 1.0uF capacitor.  After doing this modification, re-test the pcb.

I see you have location for XRES pull-up resistor and capacitor.  This is good.  You can increase the capacitor to 1uF as this will give more RESET state as power supply rises in voltage.  I will say, 1uF might be too much for Miniprog to discharge quickly.  So, you might need to experiment with a capacitor value in between 0.1uF-to-1uF (to have Miniprog work correctly).

Something else to try is, remove XRES pull-up resistor.  Re-test pcb.
And then, remove XRES capacitor, and re-test.
This would be similar setup as KIT-059 with PSoC 5LP.

Let us know how it goes.