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The First v0.2 Board Assembled

A project log for PD Buddy Sink

Smart power jack for USB Power Delivery

clara-hobbsClara Hobbs 05/06/2017 at 20:370 Comments

The first three v0.2 PCBs just arrived from @oshpark today. I was excited to build one, so I ran the 1.5 miles to the mailbox and back to burn off some excess energy. When I got back, I opened the envelope and found these lovely little pieces of FR4.

Then began the arduous process of hand-assembling a board with a 0.5 mm pitch QFN and USB Type-C connector. Not too scary, especially with a vacuum pick-up tool, but still not easy.

After about two hours of soldering, I had a beautiful board assembled. Those 10 kΩ and 2 kΩ SMD resistors look almost exactly the same, don't they?

I bought STM32F072C8T MCUs for these instead of the STM32F072CBT I used on the v0.1 boards. They're almost exactly the same, except the chip on the new board has only 64 KiB of flash instead of 128 KiB. Since the firmware is only about 28 KiB, the smaller chip still has plenty of room for expansion, and costs less too. I had to make a few changes to the firmware to support the smaller flash, but that went very smoothly.

All in all, I'm really happy with how the new board came out. It's a fairly minor revision compared to what v0.3 will bring, but it has a lot of little improvements that make the Sink so much nicer. The USB connector hangs off the board farther, so enclosure walls can be thicker. The current carrying traces are thicker, so the board shouldn't even get warm when it's carrying 5 A. Plus, no rework is needed in the output circuit, so that's nice.

Onward to v0.3!

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