5 years, 1 month ago.

4 Digit Display not working with LPC1114FN28

Hi. Is there any reason why the 4 digit display would not work with the LPC1114FN28? I've imported the library and basically copied everything from a working KL25Z program - it's just a simple second counter - and can see signals on the DIO and CLK pins, but there's no display. Yes, I have Vdd and Vss properly connected. I have a separate LED that blinks in time with what should be displayed on the 4 digit display, and that works, so I have every reason to believe the program is correct.

Any insight would be appreciated. Thanks!

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1 Answer

5 years, 1 month ago.

Make sure you did not reverse the DIO and CLK pins. What supply voltage are you using for the display. Is it 5V or 3V3? Maybe the 3V3 levels on the LPC1114 are below the minimal threshold needed for the display when running it at 5V. I have noticed some issues with that on some display drivers.

I tried both: Switching the pins both physically and in the software; and using 5v and 3.3. It works with 5V with the KL25Z; I didn't try 3.3 with the KL25. When powering the display using the 1114, I connected the display power pins to the supply rails, so the 1114 wasn't providing power for that. But, the more fundamental answer is No, I guess: there's nothing inherently incompatible between the 1114 and the four digit display. Is that correct?

posted by Aaron Minner 01 Jan 2018

Well what the... I tried using dp1 / dp2 and it worked - at both 3.3 & 5v. Then, to make sure it wasn't limited to certain pins, I tried dp17 / dp18, and that works, too. Maybe these old eyes - even with reading glasses - couldn't see which pins I was actually using, initially. Oi. Anyway, it's working, now. Sorry for the false alarm.

posted by Aaron Minner 02 Jan 2018