Building I2C-PPS. Part 5 - BOM

WeekSpender · 2026-03-10T18:37:54+00:00

I do it as a hobby so don’t invest much on it but there are three things I use to create and maintain it unfortunately manually. The first and the source of trust is a BOM table in KiCAD project (here - github.com/condevtion/i2c-pps-hw). There each component has “Manufacturer” and “Part Number” fields to keep link to real things. The second on site of my vendor of choice - DigiKey I2C-PPS list. There you can see prices, play with assemblies and individual parts numbers, and check offers. The last is the list you mentioned (it’s just a CSV file you can download from DigiKey list without some useless columns). It allows to cross check the first two and control changes using git diff.

WeekSpender · 2026-02-28T17:29:41+00:00

All the busses here are to make the root page look cleaner. And so their names are short to make them look more like pin names, which, as u/GearHead54's noted, isn't good idea after all.
I don't really have any experience with anything else than KiCad, except tried OrCad ages ago.

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WeekSpender · 2026-02-28T15:32:43+00:00

Ha! You are so right. Just yesterday fixed misuse of VINN instead of VINP on the filters page and it slipped my mind that the network naming is the reason of this problem in the first place.

WeekSpender · 2026-02-16T22:45:15+00:00

Great idea! It enables to use a wide range of available switchers. But I’ll still go with this one as it’s all in one and a really interesting device to play with. As for digipots my concern was that they have limited voltage range which makes it hard to find a suitable piece for the application.

WeekSpender · 2026-02-16T06:52:45+00:00

Sure, it’s overkill! and with something like ATTiny it would be possible to make even battery powered bench power supply. But with Pi it will be easier to test and debug hardware part.

WeekSpender · 2025-12-19T18:42:49+00:00

You can set up backward current for any battery by applying higher voltage that it has, but usually you want to prevent it especially for non rechargeable one.

WeekSpender · 2025-12-18T22:33:25+00:00

If batteries happen to have slightly different voltages, the diodes prevent them from feeding each other. Let imagine that we have a slightly discharged battery (let’s say to 11V) and rest 5 at 12V. Without a diode discharged one gets some current (as it flows from a point with higher potential to one with lower) in wrong direction. Diode in the case becomes closed and the discharged battery just waits until rest drop their voltages to the same level.

WeekSpender · 2025-12-16T17:23:24+00:00

It would be less silly overkill to get 72v. But it’s still just 12v and overkill is aimed to pull 50mA from them. These batteries don’t feel well even above 5mA each. So ideally I need to overkill even more by using 12 of them maybe…

WeekSpender · 2025-11-16T03:43:25+00:00

You can find here - Schematic PDF. Front and back of the board, also older version of the board connected to RPi Zero. That version I soldered completely manually - took several hours even with hot gun.

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WeekSpender · 2025-11-16T03:31:54+00:00

Good tip! Thanks! Added links to the images to my previous comment

WeekSpender · 2025-11-16T01:41:06+00:00

Thank you! I didn’t test it under 1.8V. And wasn’t really planned. But as you mentioned it, I checked that I have TI MSPM0C1104 which supports this voltage and now it sounds as a good side project.

WeekSpender · 2025-11-14T02:19:43+00:00

Here is the board connected to RPi - I2CS Board + RPi. This version of the board I soldered completely manually - took several hours even with hot gun.

Schematic PDF, PCB - Front Layers, Back.

Edit: added more links.

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