So the new revision is finally out! The processor is so small it took me extra time to make sure it’s in the right spot. The pitch between the small processor’s pads is 0.45mm or 0.018 inches so I can’t miss by half of that, usually 1/4 of the pitch, thus 0.0044 inches of tolerance, so less than 5 mils. The following shows how small the processor is. Overall it is 4mm (0.16 inches) wide (see E).
Another change is the protection diode. To deal with constant shortage of various parts, I’ve added a surface-mount diode of the same type near the top right terminal block, the little black box. This way if I run out of the big orange diode I can use the surface mount ones. The two diodes are literally the same, just packaged differently, same for the processors. I have about a dozen or less of the current revision (Oct 2021) and will start making the new revisions since I literally will run out of both Oct 2021 revision boards and processors this week. I will have plenty of the new revision boards, enough for this year and maybe even part of next year!
The above is an order of 9 adapters. So if you have received your order of SDI-12 USB adapters in a stack of boards, hope you will make good use of the M3 standoffs! I’ve been shipping bulk quantities of the adapters lately due to an increase of quantities per order. I thought, the anti-static bags are cheap but are waste once the adapter has been received. So if I could pack the adapters better, I may be able to ship more adapters with a more compact box. Also the standoffs are nice to have for anyone who will mount the adapters in boxes. If there has been any problems with this bulk packaging, please let me know!
Due to the chip shortage, I was unable to make more batches of USB adapters lately and the stock has gone down to zero for some time. Lately I’ve found a small batch of chips to make two small batches to fill out recent orders and have some extra to sell on my square store again. This small batch of chips will not last very long. There’s about a dozen of SDI-12 USB adapters and a few SDI-12 + Analog USB adapters that are in stock. Meanwhile, I’ve sourced a different processor package and am in the process of making updates to my designs to use these new processors. Here is a comparison between the existing processor package (TQFP-32) on the left and the new processor package (QFN-28) on the right.
As you can see, the new package is quite a bit smaller and you can’t even see any pins as there aren’t any. There are metal pads under the processor. The only difference between the processors is how the processor is packaged. The existing adapters use the thin-quad-flat-pack with 32 pins while the new adapters will be using the quad-flat-pack-no-pin with 28 pins. The 4 missing pins are not used by the adapter so there’s no difference. Since the new design is still under development/prototype stage, I’ll still be selling remaining adapters based on the existing design until I completely run out of parts to make them, which is very soon. Here is a comparison of the existing and new designs. The one on the right with a smaller processor at the bottom is the new design:
So not too much has changed. I do, on the other hand, have a new variant that I want to float here: Remove the 12-pole connector at the top. Replace it with a 5V->12V boost converter. This will also remove the power selection jumper and external power terminal because the adapter will provide 12V with the boost converter. Having a 12V is more desirable than the default 5V from USB because some sensors require 12V or minimal 7.5V to operate and you must attach an AC adapter. If you see the benefit of such a variant (my main design remains unchanged), please respond so I can gauge the level of interest. Once my prototyping is done and I’m certain my design works fine, I can make a small batch of the variants that have the boost converter if there’s enough interest. Here is what it looks like:
I have added a 5th terminal for SDI-12 sensors where the external power terminal was. The tentative price is $59. It saves you from having to purchase a separate 12V adapter for each USB adapter and the hassle to wire the adapter. Since I removed the 12-pole terminal and the associated 4 analog pins, it makes routing easier and I used a double footprint of the processor so the board can be assembled with either processor.
