An improved dsPIC-EL-GM

It was way back in 2012 when I first started thinking about a dsPIC-EL, but it was 2015 when I finally broke down and sent a PCB to production.  Since then the dsPIC-EL-GM has been the foundation for dozens, maybe hundreds of projects.

Recently I find I am dealing with many more 3 volt parts, and I often end up building a 3V3 supply on whatever shield I am making at the time.  The basic board has plenty of proto space which I never use, so why not sacrifice some of that for a 3 volt regulator?  The Arduino shield has a pin for 3 volts, so that wasn't a big deal.

3V3 supply

Turns out to have been a pretty simple change, and I was running out of boards and probably would need to order more anyway.  The one disappointment was that I paid extra for DHL shipping, and due to customs delays, Chinese holidays, etc. the board took almost as long as free shipping. Well, that and Maker Studio no longer makes custom boards so I had to search out other suppliers.

Things have changed over the past few years. The price of Chinese boards has come down a little, but the price for U.S. made boards has exploded. It used to cost less than three times as much for a U.S. board over a Chinese board. Now it is more than ten times. Plus, I can get Chinese boards just as quickly as U.S. boards, so even paying a premium for fast shipping, they are still a lot cheaper.

One minor annoyance in the old board was that the contrast pot for the LCD couldn't be adjusted when a shield was in place. I tried drilling a hole in the shield, and even laid out a new shield PCB (but never ordered it).  It occurred to me that I could fit a vertical pot under the LCD.

New contrast pot location

With that change, I could now adjust the LCD contrast without messing with the shield.  (Yes, I know, how often do you need to do that. Well, I play with various LCDs, kind of a fetish I have, so I probably twiddle that pot more than the average bear.)

While I was at it, I decided I would change the bypass caps out for SMT caps. Don't know why, I have hundreds of 0.1 and 0.01 monolithics in the parts drawer, but it seemed like the thing to do.  What I didn't do is change out the resistors, which I probably should have.

dsPIC-EL-GM full board

The other thing I really should have done is used SMT LEDs. The 5mm LEDs sometimes get in the way. On one instance I did tack SMT LEDs on to the through hole pads, and that worked quite well.

I'm pretty pleased with this board. Although there are a few things I would like to change, nothing is really pressing, so probably this will be the last change for a while.

As always, the PCB file, Gerbers, etc are all in gitlab. This version is in the Rev2 branch.

Soldering the micro-USB

The previous post raised some questions about how difficult it is to deal with the micro-USB connector.  The connector in question is an FCI 10103593, a devilishly tiny little thing but really, not all that hard to deal with.

Top view of the connector

Bottom view of the connector

The pads on the PCB in question are only complete for the power and ground pins

PCB pad

Before starting, it can be helpful to bend the required pins down a little, and the unnecessary pins up and out of the way

Bent pins

The first step is to tack down one corner with the pins properly aligned.  

Step 1

Then, you can take a close look with a magnifying glass and verify that the pins are aligned.  With only one corner tacked down it is easy to re-heat the pad and re-position the jack.

Once you are comfortable that the pins are properly aligned, tack down the other three corners so the part is now secure.

Step 2

Finally, heat the Vdd pad and flow a little solder onto the pad.  Wait a bit with heat on the pad and the pin will heat up and wick the solder onto the pin. 

Step 3

If you should get a little heavy on the solder, desoldering braid is a wonderful thing!