7 years, 8 months ago.

difference in powering the LPC1768

Hi All,

I have moved a LPC1768 with a 16x2 LCD-module from a breadboard to a special cabinet and the power supply therefore changed from USB to Vin (p2) with a 9V battery. Now the display isn't working anymore and while searching for the error I measured only ca. +1V at VU (p39). I changed back to a USB power supply and I measured +5V at VU again. Alas this didn't brought back the LCD.

All this mess leaves me with the following questions: 1) Is there a difference in providing the power via USB and Vin (p2) so that the output voltage change from +5V to ca.+1V at VU (p39) is explainable?

2) Could the LCD-module have been damaged by powering the LPC1768 with +9V at VIN (p2)?

3) What would be a good approach to find the fault?

Any hint will be very much appriated - thank you very much in advance.

Best regards

Karl.

2 Answers

7 years, 8 months ago.

1. Yep, Vu is a direct connection of the USB power supply. No USB power supply, no power there. So what you are seeing is correct.

2. Nop. See 1: There is simply no power on the pin, but also no 9V or something similar. It shouldn't in any way be able to damage your module.

3. That your LCD still doesn't work? Check your wiring I would say.

For power there are some options. If your LCD accepts 3.3V (no idea if they do) you could use the 3.3V output, that is always available. You could use an 7805 IC to generate 5V. Or use a USB wall adapter, preferably one of those which just have a female USB slot you can put any USB cable in.

7 years, 8 months ago.

Hi Erik,

thanks a lot for your fast answer. I'm going to doublecheck the wiring and check which power option (3.3 V or 5V with 7805) is best.

Best regards

Karl