SP511E Upgrade project

Here’s my upgrade of the Standard SP511e to support 3 strips from a choice of 6 possible outputs. Why 6? because they were the “easiest” to wire up on the board given my tools and soldering skills. The ones I chose were GPIO’s 1,2,3,13,14,15.
I will say right off, this is not a project for the impatient or faint of skill.
These boards are tiny and the traces and SMD components are sized accordingly.
Feel free to scale back what I’ve shown here if you only need part of the solution.

Shopping list:
Level shifter
I’m a fan of using 74HCT/ACT class of IC’s as level shifters. I have a few 74ACT245’s, so I used that. The advantage is it gives you 8 channels of shifters in one package, the downside is it may be a little bigger than you like. I’m using the SOIC package so the size worked out OK. If you want to use a 74HCT125 (or 74HCT08, or a bunch of other possibilities) that will work fine. You’ll just get 4 channels instead of 8.

Wire
Did I mention these boards are tiny? they are. Optical help to see what you’re doing is going to be a must. And to match that the hookup wire you use will need to be scaled down from what you’re used to seeing. Cat5 wire (24AWG) is way too big. I settled on 30AWG wirewrap wire. It’s fairly strong, solders well and most importantly will fit the tiny thru-holes on the board.

Output Strip
I went all out and included a screw terminal strip to give me easy access to 5 outputs plus ground. Many will probably scale this back to just enabling the 2nd output wire or perhaps adding a 3rd as the board will only support 3 strips at the moment.

The process
Here we go! The first thing you need to do is identify the spots on the board to attach the wires. This diagram will probably help:

When using these spots, Take Your Time. You’re better off getting the spot clean and ready for solder rather than forcing a wire through and just trying to “heat the dirty bits away”. Long applications of heat are not your friend here. I use a straight pin to try and gently ream the thru-hole from both sides of the board. Once I can see light through the hole I’ll try a piece of stripped 30AWG from the top side and move it through a few times. If it moves easily, try a dab of solder on the bottom side of the board. You can usually tell if its spreading nicely. If you’re soldering to an SMD part (like the PWR wire), don’t heat more than you have to, you’ll risk desoldering the part and causing a real mess. You may want to check for continuity from the end of the soldered wire to some other part of the trace with a meter.

When you’ve done the connections (including Pwr and Gnd), the board can look like this:

Then you’ll add in the level shifter:

You’ll change from -

To this -

The Level Shifter board just “floats” above the main board. There’s enough connections in my setup to reliably hold it together. I left the level shifter floating as that should help to let the heat from the main board dissipate. You can see where I’ve spliced in the level shifted GPIO15 to the second output plug (the heavier white wire).

Clean up the details and you’ll get -

Or up close -

Hope that helps to get a few more people started…

2 Likes

If you use 2 or 13 you’ll lose buttons. What pin is the easiest to get to without losing functionality?

The factory default use for GPIO’s is -
2 - PWR button
13 - M Button
14 - S Button
3 - LED drive for both connectors

1 - TX pad
15 - Nothing, but 10K0 pulldown res. (Edit, corrected pulldown, not pullup 2021-10-15)

If you want to keep all your buttons, you can pretty easily get 1 and/or 15.
The pulldown on 15 might might cause some issues but it’s a fairly large value and has worked well for me in the cases I’ve tried.
GPIO 1 will be pretty bullet proof, keep in mind that the point I’ve labelled is after a 100R resistor. It shouldn’t have much of any effect, especially if you add your own level shifter.

So 1 is a fairly easy thru-hole attach and 15 is not too bad either, although it is on one side of an SMD resistor. As I said before, BIG soldering irons won’t be a help here.